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L_0248 | natural gas power | T_1482 | Like crude oil, natural gas must be processed before it can be used as a fuel. Some of the chemicals in unprocessed natural gas are poisonous to humans. Other chemicals, such as water, make the gas less useful as a fuel. Processing natural gas removes almost everything except the methane. Once the gas is processed, it is ready to be delivered and used. Natural gas is delivered to homes for uses such as cooking and heating. Like coal and oil, natural gas is also burned to generate heat for powering turbines. The spinning turbines turn generators, and the generators create electricity. Click image to the left or use the URL below. URL: | text | null |
L_0248 | natural gas power | T_1483 | Natural gas burns much cleaner than other fossil fuels, meaning that it causes less air pollution. Natural gas also produces less carbon dioxide than other fossil fuels do for the same amount of energy, so its global warming effects are less (Figure 1.2). Unfortunately, drilling for natural gas can be environmentally destructive. One technique used is hydraulic fractur- ing, also called fracking, which increases the rate of recovery of natural gas. Fluids are pumped through a borehole to create fractures in the reservoir rock that contains the natural gas. Material is added to the fluid to prevent the fractures from closing. The damage comes primarily from chemicals in the fracturing fluids. Chemicals that have been found in the fluids may be carcinogens (cancer-causing), radioactive materials, or endocrine disruptors, which interrupt hormones in the bodies of humans and animals. The fluids may get into groundwater or may runoff into streams and other surface waters. As noted above, fracking may cause earthquakes. Click image to the left or use the URL below. URL: | text | null |
L_0249 | natural resource conservation | T_1484 | So that people in developed nations maintain a good lifestyle and people in developing nations have the ability to improve their lifestyles, natural resources must be conserved and protected (Figure 1.1). People are researching ways to find renewable alternatives to non-renewable resources. Here is a checklist of ways to conserve resources: Buy less stuff (use items as long as you can, and ask yourself if you really need something new). Reduce excess packaging (drink tap water instead of water from plastic bottles). Recycle materials such as metal cans, old cell phones, and plastic bottles. Purchase products made from recycled materials. Reduce pollution so that resources are maintained. Prevent soil erosion. Plant new trees to replace those that are cut down. Drive cars less, take public transportation, bicycle, or walk. Conserve energy at home (turn out lights when they are not needed). Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: | text | null |
L_0250 | neptune | T_1485 | Neptune, shown in Figure 1.1, is the only major planet that cant be seen from Earth without a telescope. Scientists predicted the existence of Neptune before it was discovered because Uranus did not always appear exactly where it should appear. They knew that the gravitational pull of another planet beyond Uranus must be affecting Uranus orbit. Neptune was discovered in 1846, in the position that had been predicted, and it was named Neptune for the Roman god of the sea because of its bluish color. This image of Neptune was taken by Voy- ager 2 in 1989. The Great Dark Spot seen on the left center in the picture has since disappeared, but a similar dark spot has appeared on another part of the planet. In many respects, Neptune is similar to Uranus (Figure 1.2). Neptune has slightly more mass than Uranus, but it is slightly smaller in size. Neptune is much farther from the Sun, at nearly 4.5 billion km (2.8 billion mi). The planets slow orbit means that it takes 165 Earth years to go once around the Sun. | text | null |
L_0250 | neptune | T_1486 | Neptunes blue color is mostly because of frozen methane (CH4 ). When Voyager 2 visited Neptune in 1986, there was a large dark-blue spot, which scientists named the Great Dark Spot, south of the equator. When the Hubble Space Telescope took pictures of Neptune in 1994, the Great Dark Spot had disappeared, but another dark spot had appeared north of the equator. Astronomers think that both of these spots represent gaps in the methane clouds on Neptune. The changing appearance of Neptune is caused by its turbulent atmosphere. The winds on Neptune are stronger than on any other planet in the solar system, reaching speeds of 1,100 km/h (700 mi/h), close to the speed of sound. This extreme weather surprised astronomers, since the planet receives little energy from the Sun to power weather systems. Neptunes core is 7000 C (12,632 C) which means that it produces more energy than it receives from the Sun. Neptune is also one of the coldest places in the solar system. Temperatures at the top of the clouds are about -218 C (-360 F). Neptunes composition is that of a gas giant: (1) upper atmosphere, (2) atmo- sphere composed of hydrogen, helium and methane gas, (3) mantle of water, ammonia and methane ice, (4) core of rock and ice. | text | null |
L_0250 | neptune | T_1487 | Neptune has faint rings of ice and dust that may change or disappear in fairly short time frames. Neptune has 13 known moons. Triton, shown in Figure 1.3, is the only one of them that has enough mass to be spherical in shape. Triton orbits in the direction opposite to the orbit of Neptune. Scientists think Triton did not form around Neptune, but instead was captured by Neptunes gravity as it passed by. This image of Triton, Neptunes largest moon, was taken by Voyager 2 in 1989. | text | null |
L_0251 | nitrogen cycle in ecosystems | T_1488 | Nitrogen (N2 ) is vital for life on Earth as an essential component of organic materials, such as amino acids, chloro- phyll, and nucleic acids such as DNA and RNA (Figure 1.1). Chlorophyll molecules, essential for photosynthesis, contain nitrogen. | text | null |
L_0251 | nitrogen cycle in ecosystems | T_1489 | Although nitrogen is the most abundant gas in the atmosphere, it is not in a form that plants can use. To be useful, nitrogen must be fixed, or converted into a more useful form. Although some nitrogen is fixed by lightning or blue-green algae, much is modified by bacteria in the soil. These bacteria combine the nitrogen with oxygen or hydrogen to create nitrates or ammonia (Figure 1.2). (a) Nucleic acids contain nitrogen (b) Chlorophyll molecules contain nitrogen | text | null |
L_0251 | nitrogen cycle in ecosystems | T_1489 | Although nitrogen is the most abundant gas in the atmosphere, it is not in a form that plants can use. To be useful, nitrogen must be fixed, or converted into a more useful form. Although some nitrogen is fixed by lightning or blue-green algae, much is modified by bacteria in the soil. These bacteria combine the nitrogen with oxygen or hydrogen to create nitrates or ammonia (Figure 1.2). (a) Nucleic acids contain nitrogen (b) Chlorophyll molecules contain nitrogen | text | null |
L_0251 | nitrogen cycle in ecosystems | T_1490 | Animals eat plant tissue and create animal tissue. After a plant or animal dies or an animal excretes waste, bacteria and some fungi in the soil fix the organic nitrogen and return it to the soil as ammonia. Nitrifying bacteria oxidize the ammonia to nitrites, while other bacteria oxidize the nitrites to nitrates, which can be used by the next generation of plants. In this way, nitrogen does not need to return to a gas. Under conditions when there is no oxygen, some bacteria can reduce nitrates to molecular nitrogen. Click image to the left or use the URL below. URL: | text | null |
L_0252 | non renewable energy resources | T_1491 | Nonrenewable resources are natural resources that are limited in supply and cannot be replaced as quickly as they are used up. A natural resource is anything people can use that comes from nature. Energy resources are some of the most important natural resources because everything we do requires energy. Nonrenewable energy resources include fossil fuels such as oil and the radioactive element uranium. | text | null |
L_0252 | non renewable energy resources | T_1492 | Oil, or petroleum, is one of several fossil fuels. Fossil fuels are mixtures of hydrocarbons (compounds containing only hydrogen and carbon) that formed over millions of years from the remains of dead organisms. In addition to oil, they include coal and natural gas. Fossil fuels provide most of the energy used in the world today. They are burned in power plants to produce electrical energy, and they also fuel cars, heat homes, and supply energy for many other purposes. You can see some ways they are used in the Figure 1.1. Q: Why do fossil fuels have energy? A: Fossil fuels contain stored chemical energy that came originally from the sun. | text | null |
L_0252 | non renewable energy resources | T_1493 | When ancient plants underwent photosynthesis, they changed energy in sunlight to stored chemical energy in food. The plants used the food and so did the organisms that ate the plants. After the plants and other organisms died, their remains gradually changed to fossil fuels as they were covered and compressed by layers of sediments. Petroleum and natural gas formed from ocean organisms and are found together. Coal formed from giant tree ferns and other swamp plants. | text | null |
L_0252 | non renewable energy resources | T_1494 | When fossil fuels burn, they release thermal energy, water vapor, and carbon dioxide. The thermal energy can be used to generate electricity or do other work. The carbon dioxide is released into the atmosphere and is a major cause of global climate change. The burning of fossil fuels also releases many pollutants into the air. Pollutants such as sulfur dioxide form acid rain, which kills living things and damages metals, stonework, and other materials. Pollutants such as nitrogen oxides cause smog, which is harmful to human health. Tiny particles, or particulates, released when fossil fuels burn also harm human health. The Figure 1.2 shows the amounts of pollutants released by different fossil fuels. Natural gas releases the least pollution; coal releases the most. Petroleum has the additional risk of oil spills, which may seriously damage ecosystems. Q: Some newer models of cars and other motor vehicles can run on natural gas. Why would a natural gas vehicle be better for the environment than a vehicle that burns gasoline, which is made from oil? A: Natural gas produces much less pollution and carbon dioxide when it burns than gasoline does. So a natural gas vehicle would contribute less to global climate change, acid rain, and air pollution that harms health. Besides being better for the environment, burning natural gas instead of gasoline results in less engine wear and provides more energy for a given amount of fuel. | text | null |
L_0252 | non renewable energy resources | T_1495 | Like fossil fuels, the radioactive element uranium can be used to generate electrical energy in power plants. This source of energy is known as nuclear energy. In a nuclear power plant, the nuclei of uranium atoms are split apart into smaller nuclei in the process of nuclear fission. This process releases a tremendous amount of energy from just a small amount of uranium. The total supply of uranium in the world is quite limited, however, and cannot be replaced once it is used up. Thats why nuclear energy is a nonrenewable resource. The use of nuclear energy also produces dangerous radioactive wastes. In addition, accidents at nuclear power plants have the potential to release large amounts of harmful radiation into the environment. Q: Why is nuclear energy often considered to be greener than energy from fossil fuels? A: Unlike energy from fossil fuels, nuclear energy doesnt produce air pollution or carbon dioxide that contributes to global climate change. | text | null |
L_0253 | nuclear power | T_1496 | When the nucleus of an atom is split, it releases a huge amount of energy called nuclear energy. For nuclear energy to be used as a power source, scientists and engineers have learned to split nuclei and to control the release of energy (Figure 1.1). | text | null |
L_0253 | nuclear power | T_1497 | Nuclear power plants, such as the one seen in Figure 1.2, use uranium, which is mined, processed, and then concentrated into fuel rods. When the uranium atoms in the fuel rods are hit by other extremely tiny particles, they split apart. The number of tiny particles allowed to hit the fuel rods needs to be controlled, or they would cause a dangerous explosion. The energy from a nuclear power plant heats water, which creates steam and causes a turbine to spin. The spinning turbine turns a generator, which in turn produces electricity. Many countries around the world use nuclear energy as a source of electricity. In the United States, a little less than 20% of electricity comes from nuclear energy. | text | null |
L_0253 | nuclear power | T_1497 | Nuclear power plants, such as the one seen in Figure 1.2, use uranium, which is mined, processed, and then concentrated into fuel rods. When the uranium atoms in the fuel rods are hit by other extremely tiny particles, they split apart. The number of tiny particles allowed to hit the fuel rods needs to be controlled, or they would cause a dangerous explosion. The energy from a nuclear power plant heats water, which creates steam and causes a turbine to spin. The spinning turbine turns a generator, which in turn produces electricity. Many countries around the world use nuclear energy as a source of electricity. In the United States, a little less than 20% of electricity comes from nuclear energy. | text | null |
L_0253 | nuclear power | T_1498 | Nuclear power is clean. It does not pollute the air. However, the use of nuclear energy does create other environ- mental problems. Uranium must be mined (Figure 1.3). The process of splitting atoms creates radioactive waste, which remains dangerous for thousands or hundreds of thousands of years. As yet, there is no long-term solution for storing this waste. The development of nuclear power plants has been on hold for three decades. Accidents at Three Mile Island and Chernobyl, Ukraine verified peoples worst fears about the dangers of harnessing nuclear power (Figure 1.4). Recently, nuclear power appeared to be making a comeback as society looked for alternatives to fossil fuels. After all, nuclear power emits no pollutants, including no greenhouse gases. But the 2011 disaster at the Fukushima Daiichi Nuclear Power Plant in Japan may have resulted in a new fear of nuclear power. The cause of the disaster was a 9.0 magnitude earthquake and subsequent tsunami, which compromised the plant. Although a total meltdown was averted, the plant experienced multiple partial meltdowns, core breaches, radiation releases, and cooling failures. The plant is scheduled for a complete cold shutdown before the end of 2011. Damaged building near the site of the Chernobyl disaster. Nuclear power is a controversial subject in California and most other places. Nuclear power has no pollutants including carbon emissions, but power plants are not always safe and the long-term disposal of wastes is a problem that has not yet been solved. The future of nuclear power is murky. | text | null |
L_0253 | nuclear power | T_1498 | Nuclear power is clean. It does not pollute the air. However, the use of nuclear energy does create other environ- mental problems. Uranium must be mined (Figure 1.3). The process of splitting atoms creates radioactive waste, which remains dangerous for thousands or hundreds of thousands of years. As yet, there is no long-term solution for storing this waste. The development of nuclear power plants has been on hold for three decades. Accidents at Three Mile Island and Chernobyl, Ukraine verified peoples worst fears about the dangers of harnessing nuclear power (Figure 1.4). Recently, nuclear power appeared to be making a comeback as society looked for alternatives to fossil fuels. After all, nuclear power emits no pollutants, including no greenhouse gases. But the 2011 disaster at the Fukushima Daiichi Nuclear Power Plant in Japan may have resulted in a new fear of nuclear power. The cause of the disaster was a 9.0 magnitude earthquake and subsequent tsunami, which compromised the plant. Although a total meltdown was averted, the plant experienced multiple partial meltdowns, core breaches, radiation releases, and cooling failures. The plant is scheduled for a complete cold shutdown before the end of 2011. Damaged building near the site of the Chernobyl disaster. Nuclear power is a controversial subject in California and most other places. Nuclear power has no pollutants including carbon emissions, but power plants are not always safe and the long-term disposal of wastes is a problem that has not yet been solved. The future of nuclear power is murky. | text | null |
L_0255 | obtaining energy resources | T_1503 | Net energy is the amount of useable energy available from a resource after subtracting the amount of energy needed to make the energy from that resource available. For example, every 5 barrels of oil that are made available for use require 1 barrel for extracting and refining the petroleum. What is the net energy from this process? About 4 barrels (5 barrels minus 1 barrel). What happens if the energy needed to extract and refine oil increases? Why might that happen? The energy cost of an energy resource increases when the easy deposits of that resource have already been consumed. For example, if all the nearshore petroleum in a region has been extracted, more costly drilling must take place further offshore (Figure 1.1). If the energy cost of obtaining energy increases, the resource will be used even faster. Offshore drilling is taking place in deeper water than before. It takes a lot of energy to build a deep drilling platform and to run it. | text | null |
L_0255 | obtaining energy resources | T_1504 | The net-energy ratio demonstrates the difference between the amount of energy available in a resource and the amount of energy used to get it. If it takes 8 units of energy to make available 10 units of energy, then the net-energy ratio is 10/8 or 1.25. What does a net-energy ratio larger than 1 mean? What if the net-energy ratio is less than 1? A net-energy ratio larger than 1 means that there is a net gain in usable energy; a net-energy ratio smaller than one means there is an overall energy loss. Table 1.1 shows the net-energy ratios for some common energy sources. Energy Source Solar Energy Natural Gas Petroleum Coal-fired Electricity Net-energy Ratio 5.8 4.9 4.5 2.5-5.1 Notice from the table that solar energy yields much more net energy than other sources. This is because it takes very little energy to get usable solar energy. Sunshine is abundant and does not need to be found, extracted, or transported very far. The range for coal-fired electricity is because of the differing costs of transporting the coal. What does this suggest about using coal to generate electricity? The efficiency is greater in areas where the coal is locally mined and does not have to be transported great distances (Figure 1.2). Obtaining coal for energy takes a lot of energy. The coal must be located, extracted, refined, and transported. Because so much of the energy we use is from fossil fuels, we need to be especially concerned about using them efficiently. Sometimes our choices affect energy efficiency. For example, transportation by cars and airplanes is less energy-efficient than transportation by boats and trains. | text | null |
L_0256 | ocean ecosystems | T_1505 | Conditions in the intertidal zone change rapidly as water covers and uncovers the region and waves pound on the rocks. A great abundance of life is found in the intertidal zone (Figure 1.1). High energy waves hit the organisms that live in this zone, so they must be adapted to pounding waves and exposure to air during low tides. Hard shells protect from waves and also protect against drying out when the animal is above water. Strong attachments keep the animals anchored to the rock. In a tide pool, as in the photo, what organisms are found where and what specific adaptations do they have to that zone? The mussels on the top left have hard shells for protection and to prevent drying because they are often not covered by water. The sea anemones in the lower right are more often submerged and have strong attachments but can close during low tides. Many young organisms get their start in estuaries and so they must be adapted to rapid shifts in salinity. Organisms in a tide pool include sea stars and sea urchins. Click image to the left or use the URL below. URL: | text | null |
L_0256 | ocean ecosystems | T_1506 | Corals and other animals deposit calcium carbonate to create rock reefs near the shore. Coral reefs are the rain- forests of the oceans, with a tremendous amount of species diversity (Figure 1.2). Reefs can form interesting shapes in the oceans. Remember that hot spots create volcanoes on the seafloor. If these volcanoes rise above sea level to become islands, and if they occur in tropical waters, coral reefs will form on them. Since the volcanoes are cones, the reef forms in a circle around the volcano. As the volcano comes off the hot spot, the crust cools. The volcano subsides and then begins to erode away (Figure 1.3). Eventually, all that is left is a reef island called an atoll. A lagoon is found inside the reef. | text | null |
L_0256 | ocean ecosystems | T_1507 | The open ocean is a vast area. Food either washes down from the land or is created by photosynthesizing plankton. Zooplankton and larger animals feed on the phytoplankton and on each other. Larger animals such as whales and giant groupers may live their entire lives in the open water. How do fish survive in the deepest ocean? The few species that live in the greatest depths are very specialized (Figure 1.4). Since its rare to find a meal, the fish use very little energy; they move very little, breathe slowly, have minimal bone structure and a slow metabolism. These fish are very small. To maximize the chance of getting a meal, some species may have jaws that unhinge to accept a larger fish or backward-folding teeth to keep prey from escaping. Coral reefs are among the most densely inhabited and diverse areas on the globe. In this image of Maupiti Island in the South Pacific, the remnants of the volcano are surrounded by the circular reef. An 1896 drawing of a deep sea angler fish with a bioluminescent lure to attract prey. | text | null |
L_0256 | ocean ecosystems | T_1507 | The open ocean is a vast area. Food either washes down from the land or is created by photosynthesizing plankton. Zooplankton and larger animals feed on the phytoplankton and on each other. Larger animals such as whales and giant groupers may live their entire lives in the open water. How do fish survive in the deepest ocean? The few species that live in the greatest depths are very specialized (Figure 1.4). Since its rare to find a meal, the fish use very little energy; they move very little, breathe slowly, have minimal bone structure and a slow metabolism. These fish are very small. To maximize the chance of getting a meal, some species may have jaws that unhinge to accept a larger fish or backward-folding teeth to keep prey from escaping. Coral reefs are among the most densely inhabited and diverse areas on the globe. In this image of Maupiti Island in the South Pacific, the remnants of the volcano are surrounded by the circular reef. An 1896 drawing of a deep sea angler fish with a bioluminescent lure to attract prey. | text | null |
L_0256 | ocean ecosystems | T_1507 | The open ocean is a vast area. Food either washes down from the land or is created by photosynthesizing plankton. Zooplankton and larger animals feed on the phytoplankton and on each other. Larger animals such as whales and giant groupers may live their entire lives in the open water. How do fish survive in the deepest ocean? The few species that live in the greatest depths are very specialized (Figure 1.4). Since its rare to find a meal, the fish use very little energy; they move very little, breathe slowly, have minimal bone structure and a slow metabolism. These fish are very small. To maximize the chance of getting a meal, some species may have jaws that unhinge to accept a larger fish or backward-folding teeth to keep prey from escaping. Coral reefs are among the most densely inhabited and diverse areas on the globe. In this image of Maupiti Island in the South Pacific, the remnants of the volcano are surrounded by the circular reef. An 1896 drawing of a deep sea angler fish with a bioluminescent lure to attract prey. | text | null |
L_0256 | ocean ecosystems | T_1508 | Hydrothermal vents are among the most unusual ecosystems on Earth since they are dependent on chemosynthetic organisms at the base of the food web. At mid-ocean ridges at hydrothermal vents, bacteria that use chemosyn- thesis for food energy are the base of a unique ecosystem (Figure 1.5). This ecosystem is entirely separate from the photosynthesis at the surface. Shrimp, clams, fish, and giant tube worms have been found in these extreme places. Giant tube worms found at hydrothermal vents get food from the chemosynthetic bacteria that live within them. The bacte- ria provide food; the worms provide shel- ter. A video explaining hydrothermal vents with good footage is seen here: | text | null |
L_0257 | ocean garbage patch | T_1509 | Trash from land may end up as trash in the ocean, sometimes extremely far from land. Some of it will eventually wash ashore, possibly far from where it originated (Figure 1.1). | text | null |
L_0257 | ocean garbage patch | T_1510 | Although people had once thought that the trash found everywhere at sea was from ships, it turns out that 80% is from land. Some of that is from runoff, some is blown from nearshore landfills, and some is dumped directly into the sea. The 20% that comes from ships at sea includes trash thrown overboard by large cruise ships and many other vessels. It also includes lines and nets from fishing vessels. Ghost nets, nets abandoned by fishermen intentionally or not, float the seas and entangle animals so that they cannot escape. Containers sometimes go overboard in storms. Some noteworthy events, like a container of rubber ducks that entered the sea in 1992, are used to better understand ocean currents. The ducks went everywhere! | text | null |
L_0257 | ocean garbage patch | T_1511 | About 80% of the trash that ends up in the oceans is plastic. This is because a large amount of the trash produced since World War II is plastic. Also many types of plastic do not biodegrade, so they simply accumulate. While many types of plastic photodegrade that is, they break up in sunlight this process only works when the plastics are dry. Plastic trash in the water does break down into smaller pieces, eventually becoming molecule-sized polymers. Other trash in the oceans includes chemical sludge and materials that do biodegrade, like wood. | text | null |
L_0257 | ocean garbage patch | T_1512 | Some plastics contain toxic chemicals, such as bisphenol A. Plastics can also absorb organic pollutants that may be floating in the water, such as the pesticide DDT (which is banned in the U.S. but not in other nations) and some endocrine disruptors. | text | null |
L_0257 | ocean garbage patch | T_1513 | Trash from the lands all around the North Pacific is caught up in currents. The currents bring the trash into the center of the North Pacific Gyre. Scientists estimate that it takes about six years for trash to move from west coast of North America to the center of the gyre. The concentration of trash increases toward the center of the gyre. While recognizable pieces of garbage are visible, much of the trash is tiny plastic polymers that are invisible but can be detected in water samples. The particles are at or just below the surface within the gyre. Plastic confetti-like pieces are visible beneath the surface at the gyres center. This albatross likely died from the plastic it had ingested. The size of the garbage patch is unknown, since it cant be seen from above. Some people estimate that its twice the size of continental U.S, with a mass of 100 million tons. | text | null |
L_0257 | ocean garbage patch | T_1513 | Trash from the lands all around the North Pacific is caught up in currents. The currents bring the trash into the center of the North Pacific Gyre. Scientists estimate that it takes about six years for trash to move from west coast of North America to the center of the gyre. The concentration of trash increases toward the center of the gyre. While recognizable pieces of garbage are visible, much of the trash is tiny plastic polymers that are invisible but can be detected in water samples. The particles are at or just below the surface within the gyre. Plastic confetti-like pieces are visible beneath the surface at the gyres center. This albatross likely died from the plastic it had ingested. The size of the garbage patch is unknown, since it cant be seen from above. Some people estimate that its twice the size of continental U.S, with a mass of 100 million tons. | text | null |
L_0257 | ocean garbage patch | T_1514 | Marine birds, such as albatross, or animals like sea turtles, live most of their lives at sea and just come ashore to mate. These organisms cant break down the plastic and they may eventually die (Figure 1.2). Boats may be affected. Plastic waste is estimated to kill 100,000 sea turtles and marine mammals annually, but exact numbers are unknown. Plastic shopping bags are extremely abundant in the oceans. If an organism accidentally ingests one, it may clog digestion and cause starvation by stopping food from moving through or making the animal not feel hungry. In some areas, plastics have seven times the concentration of zooplankton. This means that filter feeders are ingesting a lot of plastics. This may kill the organisms or the plastics may remain in their bodies. They are then eaten by larger organisms that store the plastics and may eventually die. Fish may eat organisms that have eaten plastic and then be eaten by people. This also exposes humans to toxic chemicals that the fish may have ingested with the plastic. There are similar patches of trash in the gyres of the North Atlantic and Indian oceans. The Southern Hemisphere has less trash buildup because less of the region is continent. | text | null |
L_0258 | ocean zones | T_1515 | Oceanographers divide the ocean into zones both vertically and horizontally. | text | null |
L_0258 | ocean zones | T_1516 | To better understand regions of the ocean, scientists define the water column by depth. They divide the entire ocean into two zones vertically, based on light level. Large lakes are divided into similar regions. Sunlight only penetrates the sea surface to a depth of about 200 m, creating the photic zone ("photic" means light). Organisms that photosynthesize depend on sunlight for food and so are restricted to the photic zone. Since tiny photosynthetic organisms, known as phytoplankton, supply nearly all of the energy and nutrients to the rest of the marine food web, most other marine organisms live in or at least visit the photic zone. In the aphotic zone there is not enough light for photosynthesis. The aphotic zone makes up the majority of the ocean, but has a relatively small amount of its life, both in diversity of type and in numbers. The aphotic zone is subdivided based on depth (Figure 1.1). The average depth of the ocean is 3,790 m, a lot more shallow than the deep trenches but still an incredible depth for sea creatures to live in. What makes it so hard to live at the bottom of the ocean? The three major factors that make the deep ocean hard to inhabit are the absence of light, low temperature, and extremely high pressure. | text | null |
L_0258 | ocean zones | T_1517 | The seabed is divided into the zones described above, but ocean itself is also divided horizontally by distance from the shore. Nearest to the shore lies the intertidal zone (also called the littoral zone), the region between the high and low tidal marks. The hallmark of the intertidal is change: water is in constant motion in the form of waves, tides, and currents. The land is sometimes under water and sometimes exposed. The neritic zone is from low tide mark and slopes gradually downward to the edge of the seaward side of the continental shelf. Some sunlight penetrates to the seabed here. The oceanic zone is the entire rest of the ocean from the bottom edge of the neritic zone, where sunlight does not reach the bottom. The sea bed and water column are subdivided further, as seen in the Figure 1.1. Click image to the left or use the URL below. URL: | text | null |
L_0259 | oil spills | T_1518 | Large oil spills, like the Exxon Valdez in Alaska in 1989, get a lot of attention, as they should. Besides these large spills, though, much more oil enters the oceans from small leaks that are only a problem locally. In this concept, well take a look at a large recent oil spill in the Gulf of Mexico. | text | null |
L_0259 | oil spills | T_1519 | New drilling techniques have allowed oil companies to drill in deeper waters than ever before. This allows us to access oil deposits that were never before accessible, but only with great technological difficulty. The risks from deepwater drilling and the consequences when something goes wrong are greater than those associated with shallower wells. | text | null |
L_0259 | oil spills | T_1520 | Working on oil platforms is dangerous. Workers are exposed to harsh ocean conditions and gas explosions. The danger was never more obvious than on April 20, 2010, when 11 workers were killed and 17 injured in an explosion on a deepwater oil rig in the Gulf of Mexico (Figure 1.1). The drilling rig, operated by BP, was 77 km (48 miles) offshore and the depth to the well was more than 5,000 feet. The U.S. Coast Guard tries to put out the fire and search for missing workers after the explosion on the Deepwater Horizon drilling rig. Eleven workers were killed. | text | null |
L_0259 | oil spills | T_1521 | Two days after the explosion, the drill rig sank. The 5,000-foot pipe that connected the wellhead to the drilling platform bent. Oil was free to gush into the Gulf of Mexico from nearly a mile deep (Figure 1.2). Initial efforts to cap or contain the spill at or near its source all failed to stop the vast oil spill. It was not until July 15, nearly three months after the accident, that the well was successfully capped. Estimating the flow of oil into the Gulf from the well was extremely difficult because the leak was so far below the surface. The U.S. government estimates that about 4.9 million barrels entered the Gulf at a rate of 35,000 to 60,000 barrels a day. The largest previous oil spill in the United States was of 300,000 barrels by the Exxon Valdez in 1989 in Prince William Sound, Alaska. | text | null |
L_0259 | oil spills | T_1522 | Once the oil is in the water, there are three types of methods for dealing with it: 1. Removal: Oil is corralled and then burned; natural gas is flared off (Figure 1.3). Machines that can separate oil from the water are placed aboard ships stationed in the area. These ships cleaned tens of thousands of barrels of contaminated seawater each day. 2. Containment: Floating containment booms are placed on the surface offshore of the most sensitive coastal areas in an attempt to attempt to trap the oil. But the seas must be calm for the booms to be effective, and so were not very useful in the Gulf (Figure 1.4). Sand berms have been constructed off of the Louisiana coast to keep the oil from reaching shore. (a) On May 17, 2010, oil had been leaking into the Gulf for nearly one month. On that date government estimates put the maximum total oil leak at 1,600,000 barrels, according to the New York Times. (b) The BP oil spill on June 19, 2010. The government estimates for total oil leaked by this date was 3,200,000 barrels. 3. Dispersal: Oil disperses naturally over time because it mixes with the water. However, such large amounts of oil will take decades to disperse. To speed the process up, BP has sprayed unprecedented amounts of chemical dispersants on the spill. That action did not receive support from the scientific community since no one knows the risks to people and the environment from such a large amount of these harmful chemicals. Some workers may have become ill from exposure to the chemicals. | text | null |
L_0259 | oil spills | T_1522 | Once the oil is in the water, there are three types of methods for dealing with it: 1. Removal: Oil is corralled and then burned; natural gas is flared off (Figure 1.3). Machines that can separate oil from the water are placed aboard ships stationed in the area. These ships cleaned tens of thousands of barrels of contaminated seawater each day. 2. Containment: Floating containment booms are placed on the surface offshore of the most sensitive coastal areas in an attempt to attempt to trap the oil. But the seas must be calm for the booms to be effective, and so were not very useful in the Gulf (Figure 1.4). Sand berms have been constructed off of the Louisiana coast to keep the oil from reaching shore. (a) On May 17, 2010, oil had been leaking into the Gulf for nearly one month. On that date government estimates put the maximum total oil leak at 1,600,000 barrels, according to the New York Times. (b) The BP oil spill on June 19, 2010. The government estimates for total oil leaked by this date was 3,200,000 barrels. 3. Dispersal: Oil disperses naturally over time because it mixes with the water. However, such large amounts of oil will take decades to disperse. To speed the process up, BP has sprayed unprecedented amounts of chemical dispersants on the spill. That action did not receive support from the scientific community since no one knows the risks to people and the environment from such a large amount of these harmful chemicals. Some workers may have become ill from exposure to the chemicals. | text | null |
L_0259 | oil spills | T_1522 | Once the oil is in the water, there are three types of methods for dealing with it: 1. Removal: Oil is corralled and then burned; natural gas is flared off (Figure 1.3). Machines that can separate oil from the water are placed aboard ships stationed in the area. These ships cleaned tens of thousands of barrels of contaminated seawater each day. 2. Containment: Floating containment booms are placed on the surface offshore of the most sensitive coastal areas in an attempt to attempt to trap the oil. But the seas must be calm for the booms to be effective, and so were not very useful in the Gulf (Figure 1.4). Sand berms have been constructed off of the Louisiana coast to keep the oil from reaching shore. (a) On May 17, 2010, oil had been leaking into the Gulf for nearly one month. On that date government estimates put the maximum total oil leak at 1,600,000 barrels, according to the New York Times. (b) The BP oil spill on June 19, 2010. The government estimates for total oil leaked by this date was 3,200,000 barrels. 3. Dispersal: Oil disperses naturally over time because it mixes with the water. However, such large amounts of oil will take decades to disperse. To speed the process up, BP has sprayed unprecedented amounts of chemical dispersants on the spill. That action did not receive support from the scientific community since no one knows the risks to people and the environment from such a large amount of these harmful chemicals. Some workers may have become ill from exposure to the chemicals. | text | null |
L_0259 | oil spills | T_1523 | BP drilled two relief wells into the original well. When the relief wells entered the original borehole, specialized liquids were pumped into the original well to stop the flow. Operation of the relief wells began in August 2010. The original well was declared effectively dead on September 19, 2010. | text | null |
L_0259 | oil spills | T_1524 | The economic and environmental impact of this spill will be felt for many years. Many people rely on the Gulf for their livelihoods or for recreation. Commercial fishing, tourism, and oil-related jobs are the economic engines of the region. Fearing contamination, NOAA imposed a fishing ban on approximately one-third of the Gulf (Figure 1.5). Tourism is down in the region as beach goers find other ways to spend their time. Real estate prices along the Gulf have declined precipitously. This was the extent of the banned area on June 21, 2010. The Gulf of Mexico is one of only two places in the world where bluefin tuna spawn and they are also already endangered. Marine mammals in the Gulf may come up into the slick as they come to the surface to breathe. Eight national parks and seashores are found along the Gulf shores. Other locations may be ecologically sensitive habitats such as mangroves or marshlands. | text | null |
L_0259 | oil spills | T_1525 | There is still oil on beaches and in sediment on the seafloor in the region. Chemicals from the oil dispersants are still in the water. In October 2011 a report was issued that showed that whales and dolphins are dying in the Gulf at twice their normal rate. The long-term effects will be with us for a long time. Click image to the left or use the URL below. URL: | text | null |
L_0260 | overpopulation and over consumption | T_1526 | The Green Revolution has brought enormous impacts to the planet. | text | null |
L_0260 | overpopulation and over consumption | T_1527 | Natural landscapes have been altered to create farmland and cities. Already, half of the ice-free lands have been converted to human uses. Estimates are that by 2030, that number will be more than 70%. Forests and other landscapes have been cleared for farming or urban areas. Rivers have been dammed and the water is transported by canals for irrigation and domestic uses. Ecologically sensitive areas have been altered: wetlands are now drained and coastlines are developed. | text | null |
L_0260 | overpopulation and over consumption | T_1528 | Modern agricultural practices produce a lot of pollution (Figure 1.1). Some pesticides are toxic. Dead zones grow as fertilizers drain off farmland and introduce nutrients into lakes and coastal areas. Farm machines and vehicles used to transport crops produce air pollutants. Pollutants enter the air, water, or are spilled onto the land. Moreover, many types of pollution easily move between air, water, and land. As a result, no location or organism not even polar bears in the remote Arctic is free from pollution. | text | null |
L_0260 | overpopulation and over consumption | T_1529 | The increased numbers of people have other impacts on the planet. Humans do not just need food. They also need clean water, secure shelter, and a safe place for their wastes. These needs are met to different degrees in different nations and among different socioeconomic classes of people. For example, about 1.2 billion of the worlds people do not have enough clean water for drinking and washing each day (Figure 1.2). | text | null |
L_0260 | overpopulation and over consumption | T_1530 | The addition of more people has not just resulted in more poor people. A large percentage of people expect much more than to have their basic needs met. For about one-quarter of people there is an abundance of food, plenty of water, and a secure home. Comfortable temperatures are made possible by heating and cooling systems, rapid trans- portation is available by motor vehicles or a well-developed public transportation system, instant communication takes place by phones and email, and many other luxuries are available that were not even dreamed of only a few The percentage of people in the world that live in abject poverty is decreasing some- what globally, but increasing in some re- gions, such as Sub-Saharan Africa. decades ago. All of these require resources in order to be produced, and fossil fuels in order to be powered (Figure Many people refer to the abundance of luxury items in these peoples lives as over-consumption. People in developed nations use 32 times more resources than people in the developing countries of the world. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: | text | null |
L_0261 | ozone depletion | T_1531 | At this point you might be asking yourself, Is ozone bad or is ozone good? There is no simple answer to that question: It depends on where the ozone is located (Figure 1.1). In the troposphere, ozone is a pollutant. In the ozone layer in the stratosphere, ozone screens out high energy ultraviolet radiation and makes Earth habitable. | text | null |
L_0261 | ozone depletion | T_1532 | Human-made chemicals are breaking ozone molecules in the ozone layer. Chlorofluorocarbons (CFCs) are the most common, but there are others, including halons, methyl bromide, carbon tetrachloride, and methyl chloroform. CFCs were once widely used because they are cheap, nontoxic, nonflammable, and non-reactive. They were used as spray-can propellants, refrigerants, and in many other products. Once they are released into the air, CFCs float up to the stratosphere. Air currents move them toward the poles. In the winter, they freeze onto nitric acid molecules in polar stratospheric clouds (PSC) (Figure 1.2). In the spring, (1) Solar energy breaks apart oxygen molecules into two oxygen atoms. (2) Ozone forms when oxygen atoms bond together as O3 . UV rays break apart the ozone molecules into one oxygen molecule (O2 ) and one oxygen atom (O). These processes convert UV radiation into heat, which is how the Sun heats the stratosphere. (3) Under natural cir- cumstances, the amount of ozone cre- ated equals the amount destroyed. When O3 interacts with chlorine or some other gases the O3 breaks down into O2 and O and so the ozone layer loses its ability to filter out UV. the Suns warmth starts the air moving, and ultraviolet light breaks the CFCs apart. The chlorine atom floats away and attaches to one of the oxygen atoms on an ozone molecule. The chlorine pulls the oxygen atom away, leaving behind an O2 molecule, which provides no UV protection. The chlorine then releases the oxygen atom and moves on to destroy another ozone molecule. One CFC molecule can destroy as many as 100,000 ozone molecules. PSCs form only where the stratosphere is coldest, and are most common above Antarctica in the wintertime. PSCs are needed for stratospheric ozone to be de- stroyed. | text | null |
L_0261 | ozone depletion | T_1532 | Human-made chemicals are breaking ozone molecules in the ozone layer. Chlorofluorocarbons (CFCs) are the most common, but there are others, including halons, methyl bromide, carbon tetrachloride, and methyl chloroform. CFCs were once widely used because they are cheap, nontoxic, nonflammable, and non-reactive. They were used as spray-can propellants, refrigerants, and in many other products. Once they are released into the air, CFCs float up to the stratosphere. Air currents move them toward the poles. In the winter, they freeze onto nitric acid molecules in polar stratospheric clouds (PSC) (Figure 1.2). In the spring, (1) Solar energy breaks apart oxygen molecules into two oxygen atoms. (2) Ozone forms when oxygen atoms bond together as O3 . UV rays break apart the ozone molecules into one oxygen molecule (O2 ) and one oxygen atom (O). These processes convert UV radiation into heat, which is how the Sun heats the stratosphere. (3) Under natural cir- cumstances, the amount of ozone cre- ated equals the amount destroyed. When O3 interacts with chlorine or some other gases the O3 breaks down into O2 and O and so the ozone layer loses its ability to filter out UV. the Suns warmth starts the air moving, and ultraviolet light breaks the CFCs apart. The chlorine atom floats away and attaches to one of the oxygen atoms on an ozone molecule. The chlorine pulls the oxygen atom away, leaving behind an O2 molecule, which provides no UV protection. The chlorine then releases the oxygen atom and moves on to destroy another ozone molecule. One CFC molecule can destroy as many as 100,000 ozone molecules. PSCs form only where the stratosphere is coldest, and are most common above Antarctica in the wintertime. PSCs are needed for stratospheric ozone to be de- stroyed. | text | null |
L_0261 | ozone depletion | T_1533 | Ozone destruction creates the ozone hole where the layer is dangerously thin (Figure 1.3). As air circulates over Antarctica in the spring, the ozone hole expands northward over the southern continents, including Australia, New Zealand, southern South America, and southern Africa. UV levels may rise as much as 20% beneath the ozone hole. The hole was first measured in 1981 when it was 2 million square km (900,000 square miles). The 2006 hole was the largest ever observed at 28 million square km (11.4 million square miles). The size of the ozone hole each year depends on many factors, including whether conditions are right for the formation of PSCs. The September 2006 ozone hole, the largest observed (through 2013). Blue and purple colors show particularly low levels of ozone. | text | null |
L_0261 | ozone depletion | T_1534 | Ozone loss also occurs over the North Polar Region, but it is not enough for scientists to call it a hole. Why do you think there is less ozone loss over the North Pole area? The region of low ozone levels is small because the atmosphere is not as cold and PSCs do not form as readily. Still, springtime ozone levels are relatively low. This low moves south over some of the worlds most populated areas in Europe, North America, and Asia. At 40o N, the latitude of New York City, UV-B has increased about 4% per decade since 1978. At 55o N, the approximate latitude of Moscow and Copenhagen, the increase has been 6.8% per decade since 1978. Click image to the left or use the URL below. URL: | text | null |
L_0261 | ozone depletion | T_1535 | Ozone losses on human health and environment include: Increases in sunburns, cataracts (clouding of the lens of the eye), and skin cancers. A loss of ozone of only 1% is estimated to increase skin cancer cases by 5% to 6%. Decreases in the human immune systems ability to fight off infectious diseases. Reduction in crop yields because many plants are sensitive to ultraviolet light. Decreases in phytoplankton productivity. A decrease of 6% to 12% has been measured around Antarctica, which may be at least partly related to the ozone hole. The effects of excess UV on other organisms is not known. Whales in the Gulf of California have been found to have sunburned cells in their lowest skin layers, indicating very severe sunburns. The problem is greatest with light colored species or species that spend more time near the sea surface. When the problem with ozone depletion was recognized, world leaders took action. CFCs were banned in spray cans in some nations in 1978. The greatest production of CFCs was in 1986, but it has declined since then. This will be discussed more in the next concept. | text | null |
L_0262 | paleozoic and mesozoic seas | T_1536 | Some of the most important events of the Paleozoic and Mesozoic were the rising and falling of sea level over the continents. Sea level rises over the land during a marine transgression. During a marine regression, sea level retreats. During the Paleozoic there were four complete cycles of marine transgressions and regressions. There were two additional cycles during the Mesozoic (Figure 1.1). One of two things must happen for sea level to change in a marine transgression: either the land must sink or the water level must rise. What could cause sea level to rise? When little or no fresh water is tied up in glaciers and ice caps, sea level is high. Sea level also appears to rise if land is down dropped. Sea level rises if an increase in seafloor spreading rate buoys up the ocean crust, causing the ocean basin to become smaller. What could cause sea level to fall in a marine regression? Six marine transgressions and regres- sions have occurred during the Phanero- zoic. Geologists think that the Paleozoic marine transgressions and regressions were the result of the decrease and increase in the size of glaciers covering the lands. Click image to the left or use the URL below. URL: | text | null |
L_0262 | paleozoic and mesozoic seas | T_1537 | Geologists know about marine transgressions and regressions from the sedimentary rock record. These events leave characteristic rock layers known as sedimentary facies. On a shoreline, sand and other coarse grained rock fragments are commonly found on the beach where the wave energy is high. Away from the shore in lower energy environments, fine-grained silt that later creates shale is deposited. In deeper, low-energy waters, carbonate mud that later hardens into limestone is deposited. | text | null |
L_0262 | paleozoic and mesozoic seas | T_1538 | The Paleozoic sedimentary rocks of the Grand Canyon contain evidence of marine transgressions and regressions, but even there the rock record is not complete. Look at the sequence in the Figure 1.2 and see if you can determine whether the sea was transgressing or regressing. At the bottom, the Tonto Group represents a marine transgression: sandstone (11), shale (10), and limestone (9) laid down during 30 million years of the Cambrian Period. The Ordovician and Silurian are unknown because of an unconformity. Above that is freshwater limestone (8), which is overlain by limestone (7) and then shale (6), indicating that the sea was regressing. After another unconformity, the rocks of the Supai Group (5) include limestone, siltstone, and sandstone indicative of a regressing sea. Above those rocks are shale (4), sandstone (3), a limestone and sandstone mix (2) showing that the sea regressed and transgressed and finally limestone (1) indicating that the sea had come back in. | text | null |
L_0263 | paleozoic plate tectonics | T_1539 | The Paleozoic is the furthest back era of the Phanerozoic and it lasted the longest. But the Paleozoic was relatively recent, beginning only 570 million years ago. Compared with the long expanse of the Precambrian, the Phanerozoic is recent history. Much more geological evidence is available for scientists to study so the Phanerozoic is much better known. The Paleozoic begins and ends with a supercontinent. At the beginning of the Paleozoic, the supercontinent Rodinia began to split up. At the end, Pangaea came together. | text | null |
L_0263 | paleozoic plate tectonics | T_1540 | A mountain-building event is called an orogeny. Orogenies take place over tens or hundreds of millions of years. As continents smash into microcontinents and island arcs collided, mountains rise. Geologists find evidence for the orogenies that took place while Pangaea was forming in many locations. For example, Laurentia collided with the Taconic Island Arc during the Taconic Orogeny (Figure 1.1). The remnants of this mountain range make up the Taconic Mountains in New York. The Taconic Orogeny is an example of a collision between a continent and a volcanic island arc. Laurentia experienced other orogenies as it merged with the northern continents. The southern continents came together to form Gondwana. When Laurentia and Gondwana collided to create Pangaea, the Appalachians rose. Geologists think they may once have been higher than the Himalayas are now. | text | null |
L_0263 | paleozoic plate tectonics | T_1541 | Pangaea was the last supercontinent on Earth. Evidence for the existence of Pangaea was what Alfred Wegener used to create his continental drift hypothesis, which was described in the chapter Plate Tectonics. As the continents move and the land masses change shape, the shape of the oceans changes too. During the time of Pangaea, about 250 million years ago, most of Earths water was collected in a huge ocean called Panthalassa (Figure 1.2). Click image to the left or use the URL below. URL: | text | null |
L_0264 | petroleum power | T_1542 | Oil is a liquid fossil fuel that is extremely useful because it can be transported easily and can be used in cars and other vehicles. Oil is currently the single largest source of energy in the world. | text | null |
L_0264 | petroleum power | T_1543 | Oil from the ground is called crude oil, which is a mixture of many different hydrocarbons. Crude oil is a thick dark brown or black liquid hydrocarbon. Oil also forms from buried dead organisms, but these are tiny organisms that live on the sea surface and then sink to the seafloor when they die. The dead organisms are kept away from oxygen by layers of other dead creatures and sediments. As the layers pile up, heat and pressure increase. Over millions of years, the dead organisms turn into liquid oil. | text | null |
L_0264 | petroleum power | T_1544 | In order to be collected, the oil must be located between a porous rock layer and an impermeable layer (Figure 1.1). Trapped above the porous rock layer and beneath the impermeable layer, the oil will remain between these layers until it is extracted from the rock. Oil (red) is found in the porous rock layer (yellow) and trapped by the impermeable layer (brown). The folded structure has allowed the oil to pool so a well can be drilled into the reservoir. To separate the different types of hydrocarbons in crude oil for different uses, the crude oil must be refined in refineries like the one shown in Figure 1.2. Refining is possible because each hydrocarbon in crude oil boils at a different temperature. When the oil is boiled in the refinery, separate equipment collects the different compounds. | text | null |
L_0264 | petroleum power | T_1545 | Most of the compounds that come out of the refining process are fuels, such as gasoline, diesel, and heating oil. Because these fuels are rich sources of energy and can be easily transported, oil provides about 90% of the energy used for transportation around the world. The rest of the compounds from crude oil are used for waxes, plastics, fertilizers, and other products. Gasoline is in a convenient form for use in cars and other transportation vehicles. In a car engine, the burned gasoline mostly turns into carbon dioxide and water vapor. The fuel releases most of its energy as heat, which causes the gases to expand. This creates enough force to move the pistons inside the engine and to power the car. Refineries like this one separate crude oil into many useful fuels and other chemi- cals. Click image to the left or use the URL below. URL: | text | null |
L_0264 | petroleum power | T_1546 | The United States does produce oil, but the amount produced is only about one-quarter as much as the nation uses. The United States has only about 1.5% of the worlds proven oil reserves, so most of the oil used by Americans must be imported from other nations. The main oil-producing regions in the United States are the Gulf of Mexico, Texas, Alaska, and California (Figure As in every type of mining, mining for oil has environmental consequences. Oil rigs are unsightly (Figure 1.4), and spills are too common (Figure 1.5). Click image to the left or use the URL below. URL: Offshore well locations in the Gulf of Mex- ico. Note that some wells are located in very deep water. Drill rigs at the San Ardo Oil Field in Monterey, California. | text | null |
L_0264 | petroleum power | T_1546 | The United States does produce oil, but the amount produced is only about one-quarter as much as the nation uses. The United States has only about 1.5% of the worlds proven oil reserves, so most of the oil used by Americans must be imported from other nations. The main oil-producing regions in the United States are the Gulf of Mexico, Texas, Alaska, and California (Figure As in every type of mining, mining for oil has environmental consequences. Oil rigs are unsightly (Figure 1.4), and spills are too common (Figure 1.5). Click image to the left or use the URL below. URL: Offshore well locations in the Gulf of Mex- ico. Note that some wells are located in very deep water. Drill rigs at the San Ardo Oil Field in Monterey, California. | text | null |
L_0265 | planet orbits in the solar system | T_1547 | Figure 1.1 shows the relative sizes of the orbits of the planets, asteroid belt, and Kuiper belt. In general, the farther away from the Sun, the greater the distance from one planets orbit to the next. The orbits of the planets are not circular but slightly elliptical, with the Sun located at one of the foci (see opening image). While studying the solar system, Johannes Kepler discovered the relationship between the time it takes a planet to make one complete orbit around the Sun, its "orbital period," and the distance from the Sun to the planet. If the orbital period of a planet is known, then it is possible to determine the planets distance from the Sun. This is how astronomers without modern telescopes could determine the distances to other planets within the solar system. How old are you on Earth? How old would you be if you lived on Jupiter? How many days is it until your birthday on Earth? How many days until your birthday if you lived on Saturn? Click image to the left or use the URL below. URL: The relative sizes of the orbits of planets in the solar system. The inner solar sys- tem and asteroid belt is on the upper left. The upper right shows the outer planets and the Kuiper belt. | text | null |
L_0266 | planets of the solar system | T_1548 | Since the time of Copernicus, Kepler, and Galileo, we have learned a lot more about our solar system. Astronomers have discovered two more planets (Uranus and Neptune), five dwarf planets (Ceres, Pluto, Makemake, Haumea, and Eris), more than 150 moons, and many, many asteroids and other small objects. Although the Sun is just an average star compared to other stars, it is by far the largest object in the solar system. The Sun is more than 500 times the mass of everything else in the solar system combined! Table 1.1 gives data on the sizes of the Sun and planets relative to Earth. Object Mass (Relative to Earth) Sun Mercury Venus Earth 333,000 Earths mass 0.06 Earths mass 0.82 Earths mass 1.00 Earths mass Diameter of Planet (Relative to Earth) 109.2 Earths diameter 0.39 Earths diameter 0.95 Earths diameter 1.00 Earths diameter Object Mass (Relative to Earth) Mars Jupiter Saturn Uranus Neptune 0.11 Earths mass 317.8 Earths mass 95.2 Earths mass 14.6 Earths mass 17.2 Earths mass Diameter of Planet (Relative to Earth) 0.53 Earths diameter 11.21 Earths diameter 9.41 Earths diameter 3.98 Earths diameter 3.81 Earths diameter | text | null |
L_0266 | planets of the solar system | T_1549 | Distances in the solar system are often measured in astronomical units (AU). One astronomical unit is defined as the distance from Earth to the Sun. 1 AU equals about 150 million km, or 93 million miles. Table 1.2 shows the distances to the planets (the average radius of orbits) in AU. The table also shows how long it takes each planet to spin on its axis (the length of a day) and how long it takes each planet to complete an orbit (the length of a year); in particular, notice how slowly Venus rotates relative to Earth. Planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Average Distance from Sun (AU) 0.39 AU 0.72 1.00 1.52 5.20 9.54 19.22 30.06 Length of Day (In Earth Days) 56.84 days 243.02 1.00 1.03 0.41 0.43 0.72 0.67 Length of Year (In Earth Years) 0.24 years 0.62 1.00 1.88 11.86 29.46 84.01 164.8 Click image to the left or use the URL below. URL: | text | null |
L_0268 | ponds and lakes | T_1552 | Ponds are small bodies of fresh water that usually have no outlet; ponds are often are fed by underground springs. Like lakes, ponds are bordered by hills or low rises so the water is blocked from flowing directly downhill. | text | null |
L_0268 | ponds and lakes | T_1553 | Lakes are larger bodies of water. Lakes are usually fresh water, although the Great Salt Lake in Utah is just one exception. Water usually drains out of a lake through a river or a stream and all lakes lose water to evaporation. Lakes form in a variety of different ways: in depressions carved by glaciers, in calderas (Figure 1.1), and along tectonic faults, to name a few. Subglacial lakes are even found below a frozen ice cap. As a result of geologic history and the arrangement of land masses, most lakes are in the Northern Hemisphere. In fact, more than 60% of all the worlds lakes are in Canada most of these lakes were formed by the glaciers that covered most of Canada in the last Ice Age (Figure 1.2). Lakes are not permanent features of a landscape. Some come and go with the seasons, as water levels rise and fall. Over a longer time, lakes disappear when they fill with sediments, if the springs or streams that fill them diminish, (a) Crater Lake in Oregon is in a volcanic caldera. Lakes can also form in volcanic craters and impact craters. (b) The Great Lakes fill depressions eroded as glaciers scraped rock out from the landscape. (c) Lake Baikal, ice coated in winter in this image, formed as water filled up a tectonic faults. Lakes near Yellowknife were carved by glaciers during the last Ice Age. or if their outlets grow because of erosion. When the climate of an area changes, lakes can either expand or shrink (Figure 1.3). Lakes may disappear if precipitation significantly diminishes. Large lakes have tidal systems and currents, and can even affect weather patterns. The Great Lakes in the United States contain 22% of the worlds fresh surface water (Figure 1.1). The largest them, Lake Superior, has a tide that rises and falls several centimeters each day. The Great Lakes are large enough to alter the weather system in Northeastern United States by the lake effect, which is an increase in snow downwind of the relatively warm lakes. The Great Lakes are home to countless species of fish and wildlife. Many lakes are not natural, but are human-made. People dam a stream in a suitable spot and then let the water back up behind it, creating a lake. These lakes are called "reservoirs." Click image to the left or use the URL below. URL: | text | null |
L_0268 | ponds and lakes | T_1553 | Lakes are larger bodies of water. Lakes are usually fresh water, although the Great Salt Lake in Utah is just one exception. Water usually drains out of a lake through a river or a stream and all lakes lose water to evaporation. Lakes form in a variety of different ways: in depressions carved by glaciers, in calderas (Figure 1.1), and along tectonic faults, to name a few. Subglacial lakes are even found below a frozen ice cap. As a result of geologic history and the arrangement of land masses, most lakes are in the Northern Hemisphere. In fact, more than 60% of all the worlds lakes are in Canada most of these lakes were formed by the glaciers that covered most of Canada in the last Ice Age (Figure 1.2). Lakes are not permanent features of a landscape. Some come and go with the seasons, as water levels rise and fall. Over a longer time, lakes disappear when they fill with sediments, if the springs or streams that fill them diminish, (a) Crater Lake in Oregon is in a volcanic caldera. Lakes can also form in volcanic craters and impact craters. (b) The Great Lakes fill depressions eroded as glaciers scraped rock out from the landscape. (c) Lake Baikal, ice coated in winter in this image, formed as water filled up a tectonic faults. Lakes near Yellowknife were carved by glaciers during the last Ice Age. or if their outlets grow because of erosion. When the climate of an area changes, lakes can either expand or shrink (Figure 1.3). Lakes may disappear if precipitation significantly diminishes. Large lakes have tidal systems and currents, and can even affect weather patterns. The Great Lakes in the United States contain 22% of the worlds fresh surface water (Figure 1.1). The largest them, Lake Superior, has a tide that rises and falls several centimeters each day. The Great Lakes are large enough to alter the weather system in Northeastern United States by the lake effect, which is an increase in snow downwind of the relatively warm lakes. The Great Lakes are home to countless species of fish and wildlife. Many lakes are not natural, but are human-made. People dam a stream in a suitable spot and then let the water back up behind it, creating a lake. These lakes are called "reservoirs." Click image to the left or use the URL below. URL: | text | null |
L_0268 | ponds and lakes | T_1553 | Lakes are larger bodies of water. Lakes are usually fresh water, although the Great Salt Lake in Utah is just one exception. Water usually drains out of a lake through a river or a stream and all lakes lose water to evaporation. Lakes form in a variety of different ways: in depressions carved by glaciers, in calderas (Figure 1.1), and along tectonic faults, to name a few. Subglacial lakes are even found below a frozen ice cap. As a result of geologic history and the arrangement of land masses, most lakes are in the Northern Hemisphere. In fact, more than 60% of all the worlds lakes are in Canada most of these lakes were formed by the glaciers that covered most of Canada in the last Ice Age (Figure 1.2). Lakes are not permanent features of a landscape. Some come and go with the seasons, as water levels rise and fall. Over a longer time, lakes disappear when they fill with sediments, if the springs or streams that fill them diminish, (a) Crater Lake in Oregon is in a volcanic caldera. Lakes can also form in volcanic craters and impact craters. (b) The Great Lakes fill depressions eroded as glaciers scraped rock out from the landscape. (c) Lake Baikal, ice coated in winter in this image, formed as water filled up a tectonic faults. Lakes near Yellowknife were carved by glaciers during the last Ice Age. or if their outlets grow because of erosion. When the climate of an area changes, lakes can either expand or shrink (Figure 1.3). Lakes may disappear if precipitation significantly diminishes. Large lakes have tidal systems and currents, and can even affect weather patterns. The Great Lakes in the United States contain 22% of the worlds fresh surface water (Figure 1.1). The largest them, Lake Superior, has a tide that rises and falls several centimeters each day. The Great Lakes are large enough to alter the weather system in Northeastern United States by the lake effect, which is an increase in snow downwind of the relatively warm lakes. The Great Lakes are home to countless species of fish and wildlife. Many lakes are not natural, but are human-made. People dam a stream in a suitable spot and then let the water back up behind it, creating a lake. These lakes are called "reservoirs." Click image to the left or use the URL below. URL: | text | null |
L_0269 | population size | T_1554 | Biotic and abiotic factors determine the population size of a species in an ecosystem. What are some important biotic factors? Biotic factors include the amount of food that is available to that species and the number of organisms that also use that food source. What are some important abiotic factors? Space, water, and climate all help determine a species population. When does a population grow? A population grows when the number of births is greater than the number of deaths. When does a population shrink? When deaths exceed births. What causes a population to grow? For a population to grow there must be ample resources and no major problems. What causes a population to shrink? A population can shrink either because of biotic or abiotic limits. An increase in predators, the emergence of a new disease, or the loss of habitat are just three possible problems that will decrease a population. A population may also shrink if it grows too large for the resources required to support it. | text | null |
L_0269 | population size | T_1555 | When the number of births equals the number of deaths, the population is at its carrying capacity for that habitat. In a population at its carrying capacity, there are as many organisms of that species as the habitat can support. The carrying capacity depends on biotic and abiotic factors. If these factors improve, the carrying capacity increases. If the factors become less plentiful, the carrying capacity drops. If resources are being used faster than they are being replenished, then the species has exceeded its carrying capacity. If this occurs, the population will then decrease in size. | text | null |
L_0269 | population size | T_1556 | Every stable population has one or more factors that limit its growth. A limiting factor determines the carrying capacity for a species. A limiting factor can be any biotic or abiotic factor: nutrient, space, and water availability are examples (Figure 1.1). The size of a population is tied to its limiting factor. What happens if a limiting factor increases a lot? Is it still a limiting factor? If a limiting factor increases a lot, another factor will most likely become the new limiting factor. This may be a bit confusing, so lets look at an example of limiting factors. Say you want to make as many chocolate chip cookies as you can with the ingredients you have on hand. It turns out that you have plenty of flour and other ingredients, but only two eggs. You can make only one batch of cookies, because eggs are the limiting factor. But then your neighbor comes over with a dozen eggs. Now you have enough eggs for seven batches of cookies, but only two pounds of butter. You can make four batches of cookies, with butter as the limiting factor. If you get more butter, some other ingredient will be limiting. Species ordinarily produce more offspring than their habitat can support (Figure 1.2). If conditions improve, more young survive and the population grows. If conditions worsen, or if too many young are born, there is competition between individuals. As in any competition, there are some winners and some losers. Those individuals that survive to fill the available spots in the niche are those that are the most fit for their habitat. Click image to the left or use the URL below. URL: A frog in frog spawn. An animal produces many more offspring than will survive. | text | null |
L_0269 | population size | T_1556 | Every stable population has one or more factors that limit its growth. A limiting factor determines the carrying capacity for a species. A limiting factor can be any biotic or abiotic factor: nutrient, space, and water availability are examples (Figure 1.1). The size of a population is tied to its limiting factor. What happens if a limiting factor increases a lot? Is it still a limiting factor? If a limiting factor increases a lot, another factor will most likely become the new limiting factor. This may be a bit confusing, so lets look at an example of limiting factors. Say you want to make as many chocolate chip cookies as you can with the ingredients you have on hand. It turns out that you have plenty of flour and other ingredients, but only two eggs. You can make only one batch of cookies, because eggs are the limiting factor. But then your neighbor comes over with a dozen eggs. Now you have enough eggs for seven batches of cookies, but only two pounds of butter. You can make four batches of cookies, with butter as the limiting factor. If you get more butter, some other ingredient will be limiting. Species ordinarily produce more offspring than their habitat can support (Figure 1.2). If conditions improve, more young survive and the population grows. If conditions worsen, or if too many young are born, there is competition between individuals. As in any competition, there are some winners and some losers. Those individuals that survive to fill the available spots in the niche are those that are the most fit for their habitat. Click image to the left or use the URL below. URL: A frog in frog spawn. An animal produces many more offspring than will survive. | text | null |
L_0270 | precambrian continents | T_1557 | The first crust was made of basaltic rock, like the current ocean crust. Partial melting of the lower portion of the basaltic crust began more than 4 billion years ago. This created the silica-rich crust that became the felsic continents. | text | null |
L_0270 | precambrian continents | T_1558 | The earliest felsic continental crust is now found in the ancient cores of continents, called the cratons. Rapid plate motions meant that cratons experienced many continental collisions. Little is known about the paleogeography, or the ancient geography, of the early planet, although smaller continents could have come together and broken up. Geologists can learn many things about the Pre-Archean by studying the rocks of the cratons. Cratons also contain felsic igneous rocks, which are remnants of the first continents. Cratonic rocks contain rounded sedimentary grains. Of what importance is this fact? Rounded grains indicate that the minerals eroded from an earlier rock type and that rivers or seas also existed. One common rock type in the cratons is greenstone, a metamorphosed volcanic rock (Figure 1.1). Since greenstones are found today in oceanic trenches, what does the presence of greenstones mean? These ancient greenstones indicate the presence of subduction zones. Ice age glaciers scraped the Canadian Shield down to the 4.28 billion year old greenstone in Northwestern Quebec. | text | null |
L_0270 | precambrian continents | T_1559 | Places the craton crops out at the surface is known as a shield. Cratons date from the Precambrian and are called Precambrian shields. Many Precambrian shields are about 570 million years old (Figure 1.2). The Canadian Shield is the ancient flat part of Canada that lies around Hudson Bay, the northern parts of Minnesota, Wisconsin and Michigan and much of Greenland. | text | null |
L_0270 | precambrian continents | T_1560 | In most places the cratons were covered by younger rocks, which together are called a platform. Sometimes the younger rocks eroded away to expose the Precambrian craton (Figure 1.3). | text | null |
L_0270 | precambrian continents | T_1561 | During the Pre-Archean and Archean, Earths interior was warmer than today. Mantle convection was faster and plate tectonics processes were more vigorous. Since subduction zones were more common, the early crustal plates were relatively small. Since the time that it was completely molten, Earth has been cooling. Still, about half the internal heat that was generated when Earth formed remains in the planet and is the source of the heat in the core and mantle today. | text | null |
L_0271 | precambrian plate tectonics | T_1562 | By the end of the Archean, about 2.5 billion years ago, plate tectonics processes were completely recognizable. Small Proterozoic continents known as microcontinents collided to create supercontinents, which resulted in the uplift of massive mountain ranges. The history of the North American craton is an example of what generally happened to the cratons during the Precambrian. As the craton drifted, it collided with microcontinents and oceanic island arcs, which were added to the continents. Convergence was especially active between 1.5 and 1.0 billion years ago. These lands came together to create the continent of Laurentia. About 1.1 billion years ago, Laurentia became part of the supercontinent Rodinia (Figure 1.1). Rodinia probably contained all of the landmass at the time, which was about 75% of the continental landmass present today. Rodinia broke up about 750 million years ago. The geological evidence for this breakup includes large lava flows that are found where continental rifting took place. Seafloor spreading eventually started and created the oceans between the continents. The breakup of Rodinia may have triggered Snowball Earth around 700 million years ago. | text | null |
L_0277 | preventing hazardous waste problems | T_1581 | Nations that have more industry produce more hazardous waste. Currently, the United States is the worlds largest producer of hazardous wastes, but China, which produces so many products for the developed world, may soon take over the number-one spot. Countries with more industry produce more hazardous wastes than those with little industry. Problems with haz- ardous wastes and their disposal became obvious sooner in the developed world than in the developing world. As a result, many developed nations, including the United States, have laws to help control hazardous waste disposal and to clean toxic sites. As mentioned in the "Impacts of Hazardous Waste" concept, the Superfund Act requires companies to clean up contaminated sites that are designated as Superfund sites (Figure 1.1). If a responsible party cannot be identified, because the company has gone out of business or its culpability cannot be proven, the federal government pays for the cleanup out of a trust fund with money put aside by the petroleum and chemical industries. As a result of the Superfund Act, companies today are more careful about how they deal with hazardous substances. Superfund sites are located all over the nation and many are waiting to be cleaned up. The Resource Conservation and Recovery Act of 1976 requires that companies keep track of any hazardous materials they produce. These materials must be disposed of using government guidelines and records must be kept to show the government that the wastes were disposed of safely. Workers must be protected from the hazardous materials. To some extent, individuals can control the production and disposal of hazardous wastes. We can choose to use materials that are not hazardous, such as using vinegar as a cleanser. At home, people can control the amount of pesticides that they use (or they can use organic methods of pest control). It is also necessary to dispose of hazardous materials properly by not pouring them over the land, down the drain or toilet, or into a sewer or trashcan. Click image to the left or use the URL below. URL: | text | null |
L_0278 | principle of horizontality | T_1582 | Sedimentary rocks follow certain rules. 1. Sedimentary rocks are formed with the oldest layers on the bottom and the youngest on top. 2. Sediments are deposited horizontally, so sedimentary rock layers are originally horizontal, as are some vol- canic rocks, such as ash falls. 3. Sedimentary rock layers that are not horizontal are deformed. Since sedimentary rocks follow these rules, they are useful for seeing the effects of stress on rocks. Sedimentary rocks that are not horizontal must have been deformed. You can trace the deformation a rock has experienced by seeing how it differs from its original horizontal, oldest- on-bottom position. This deformation produces geologic structures such as folds, joints, and faults that are caused by stresses. | text | null |
L_0278 | principle of horizontality | T_1583 | Youre standing in the Grand Canyon and you see rocks like those in the Figure 1.1. Using the rules listed above, try to figure out the geologic history of the geologic column. The Grand Canyon is full mostly of sedimentary rocks, which are important for deciphering the geologic history of a region. In the Grand Canyon, the rock layers are exposed like a layer cake. Each layer is made of sediments that were deposited in a particular environment - perhaps a lake bed, shallow offshore region, or a sand dune. (a) The rocks of the Grand Canyon are like a layer cake. (b) A geologic column showing the rocks of the Grand Canyon. In this geologic column of the Grand Canyon, the sedimentary rocks of groups 3 through 6 are still horizontal. Group 2 rocks have been tilted. Group 1 rocks are not sedimentary. The oldest layers are on the bottom and youngest are on the top. The ways geologists figure out the geological history of an area will be explored more in the chapter Earth History. Click image to the left or use the URL below. URL: | text | null |
L_0279 | principle of uniformitarianism | T_1584 | The outcrop in the Figure 1.1 is at Checkerboard Mesa in Zion National Park, Utah. It has a very interesting pattern on it. As a geology student you may ask: how did this rock form? If you poke at the rock and analyze its chemistry you will see that its made of sand. In fact, the rock formation is called the Navajo sandstone. But knowing that the rock is sandstone doesnt tell you how it formed. It would be hard to design an experiment to show how this rock formed. But we can make observations now and apply them to this rock that formed long ago. | text | null |
L_0279 | principle of uniformitarianism | T_1585 | James Hutton came up with this idea in the late 1700s. The present is the key to the past. He called this the principle of uniformitarianism. It is that if we can understand a geological process now and we find evidence of that same Checkerboard Mesa in Zion National Park, Utah. process in the past, then we can assume that the process operated the same way in the past. Hutton speculated that it has taken millions of years to shape the planet, and it is continuing to be changed. He said that there are slow, natural processes that changed, and continue to change, the planets landscape. For example, given enough time, a stream could erode a valley, or sediment could accumulate and form a new landform. Lets go back to that outcrop. What would cause sandstone to have layers that cross each other, a feature called cross-bedding? | text | null |
L_0279 | principle of uniformitarianism | T_1586 | In the photo of the Mesquite sand dune in Death Valley National Park, California (Figure 1.2), we see that wind can cause cross-bedding in sand. Cross-bedding is due to changes in wind direction. There are also ripples caused by the wind waving over the surface of the dune. Since we can observe wind forming sand dunes with these patterns now, we have a good explanation for how the Navajo sandstone formed. The Navajo sandstone is a rock formed from ancient sand dunes in which wind direction changed from time to time. This is just one example of how geologists use observations they make today to unravel what happened in Earths past. Rocks formed from volcanoes, oceans, rivers, and many other features are deciphered by looking at the geological work those features do today. Click image to the left or use the URL below. URL: | text | null |
L_0280 | principles of relative dating | T_1587 | Early geologists had no way to determine the absolute age of a geological material. If they didnt see it form, they couldnt know if a rock was one hundred years or 100 million years old. What they could do was determine the ages of materials relative to each other. Using sensible principles they could say whether one rock was older than another and when a process occurred relative to those rocks. | text | null |
L_0280 | principles of relative dating | T_1588 | Remember Nicholas Steno, who determined that fossils represented parts of once-living organisms? Steno also noticed that fossil seashells could be found in rocks and mountains far from any ocean. He wanted to explain how that could occur. Steno proposed that if a rock contained the fossils of marine animals, the rock formed from sediments that were deposited on the seafloor. These rocks were then uplifted to become mountains. This scenario led him to develop the principles that are discussed below. They are known as Stenos laws. Stenos laws are illustrated in Figure 1.1. Original horizontality: Sediments are deposited in fairly flat, horizontal layers. If a sedimentary rock is found tilted, the layer was tilted after it was formed. Lateral continuity: Sediments are deposited in continuous sheets that span the body of water that they are deposited in. When a valley cuts through sedimentary layers, it is assumed that the rocks on either side of the valley were originally continuous. Superposition: Sedimentary rocks are deposited one on top of another. The youngest layers are found at the top of the sequence, and the oldest layers are found at the bottom. (a) Original horizontality. (b) Lateral continuity. (c) Superposition. | text | null |
L_0280 | principles of relative dating | T_1589 | Other scientists observed rock layers and formulated other principles. Geologist William Smith (1769-1839) identified the principle of faunal succession, which recognizes that: Some fossil types are never found with certain other fossil types (e.g. human ancestors are never found with dinosaurs) meaning that fossils in a rock layer represent what lived during the period the rock was deposited. Older features are replaced by more modern features in fossil organisms as species change through time; e.g. feathered dinosaurs precede birds in the fossil record. Fossil species with features that change distinctly and quickly can be used to determine the age of rock layers quite precisely. Scottish geologist, James Hutton (1726-1797) recognized the principle of cross-cutting relationships. This helps geologists to determine the older and younger of two rock units (Figure 1.2). If an igneous dike (B) cuts a series of metamorphic rocks (A), which is older and which is younger? In this image, A must have existed first for B to cut across it. | text | null |
L_0280 | principles of relative dating | T_1590 | The Grand Canyon provides an excellent illustration of the principles above. The many horizontal layers of sedi- mentary rock illustrate the principle of original horizontality (Figure 1.3). The youngest rock layers are at the top and the oldest are at the bottom, which is described by the law of superposition. Distinctive rock layers, such as the Kaibab Limestone, are matched across the broad expanse of the canyon. These rock layers were once connected, as stated by the rule of lateral continuity. The Colorado River cuts through all the layers of rock to form the canyon. Based on the principle of cross- cutting relationships, the river must be younger than all of the rock layers that it cuts through. | text | null |
L_0281 | processes of the water cycle | T_1591 | The movement of water around Earths surface is the hydrological (water) cycle (Figure 1.1). Water inhabits reservoirs within the cycle, such as ponds, oceans, or the atmosphere. The molecules move between these reservoirs by certain processes, including condensation and precipitation. There are only so many water molecules and these molecules cycle around. If climate cools and glaciers and ice caps grow, there is less water for the oceans and sea level will fall. The reverse can also happen. The following section looks at the reservoirs and the processes that move water between them. | text | null |
L_0281 | processes of the water cycle | T_1592 | The Sun, many millions of kilometers away, provides the energy that drives the water cycle. Our nearest star directly impacts the water cycle by supplying the energy needed for evaporation. | text | null |
Subsets and Splits