1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu ES 4. Energy enters the Earth system primarily as solar radiation and eventually escapes as heat. ES 7. Each element on Earth moves among reservoirs in the solid Earth, oceans, atmosphere, and organisms as part of biogeochemical cycles. CH 2 EARTH AS A SYSTEM

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth Basics Earth formed about 4.6 billion years ago. Is made mostly of rock. About 70% of Earth’s surface is covered oceans.

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Earth’s Interior Through studies of seismic waves. Seismic waves - vibrations that travel through Earth, are caused by earthquakes or explosions near Earth’s surface.

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth’s Interior, continued Compositional Zones of Earth’s Interior Crust - the thin/solid outermost layer of Earth that lies above the mantle Mantle - the layer of rock that lies between Earth’s crust and core nearly 2,900 km thick Core - central part of Earth that lies below the mantle

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth’s Interior, continued Structural Zones of Earth’s Interior lithosphere - solid, outer layer of Earth Made of the crust and upper part of mantle between 15km and 300 km thick. asthenosphere - solid, plastic layer of mantle made of mantle rock (flows very slowly) allows tectonic plates to move on top of it about 200 km thick.

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth’s Interior, continued Structural Zones of Earth’s Interior, continued Mesosphere - the “middle sphere” has a depth of about 2,900 km. Outer Core - Below the mesosphere, made of liquid. Inner Core – made of solid, begins at a depth of 5,150 km.

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth: A Unique Planet Chapter 2 Earth’s Interior, continued The diagram below shows the layers of Earth’s interior.

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth as a Magnet Motions within the liquid iron of Earth’s outer core produce electric currents that create Earth’s magnetic field.

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth’s Gravity Gravity is the force of attraction that exists between all matter in the universe. The larger the masses of two objects are and the closer together the objects are, the greater the force of gravity between the objects will be.

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth’s Gravity, continued Weight and Mass Weight - a measure of the strength of the pull of gravity on an object. Mass – amount of matter in an object. Measured in grams.

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth-System Science Closed Systems A closed system is a system in which energy, but not matter is exchanged with the surroundings. Open Systems An open system is a system in which both energy and matter are exchanged with the surroundings.

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth-System Science, continued The figure below compares open and closed systems.

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Earth’s Energy Budget, continued The figure below shows Earth’s energy budget.

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth’s Energy Budget, continued Internal Sources of Energy 1. radioactive decay 2. gravitational contraction 3. convection

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Earth’s Energy Budget, continued External Energy Sources 1. Most important external energy source = SUN. Solar radiation warms Earth’s atmosphere and surface. Causes movement of air masses = winds and ocean currents. 2. Gravitational energy from the moon and sun. helps generate tides = currents and mixing of ocean water.

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 2 Cycles in the Earth System A cycle - group of processes where matter and energy are cycled through reservoirs. A reservoir - a place where matter or energy is stored. The length of time that energy or matter spends in a reservoir can vary from a few hours to several million years.

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Cycles in the Earth System, continued The Nitrogen Cycle In the nitrogen cycle, nitrogen moves from the air to soil, from soil to plants and animals, and back to air again. Nitrogen is removed from air mainly by the action of nitrogen-fixing bacteria in the soil. The nitrogen enters plants, which are eaten by animals. The nitrogen is returned to the soil by decay and by animal wastes. Chemical processes that occur in the soil then release the nitrogen back into the air.

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Cycles in the Earth System, continued The figure below illustrates the nitrogen cycle.

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Cycles in the Earth System, continued The Carbon Cycle Carbon moves through all four spheres through the carbon cycle. In the short-term carbon cycle, plants convert carbon dioxide, CO 2, from the atmosphere into carbohydrates. When organisms’ bodies break down the carbohydrates and release some of the carbon back into the air as CO 2 or through their organic wastes as CO 2 or methane, CH 4. In the long-term carbon cycle, carbon is stored in the geosphere in a type of rock called a carbonate.

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Cycles in the Earth System, continued The figure below illustrates the carbon cycle.

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Cycles in the Earth System, continued The Phosphorus Cycle During the phosphorus cycle, phosphorus moves through every sphere except the atmosphere. Phosphorus enters soil and water when rock breaks down, when phosphorus in rock dissolves in water, or when organisms excrete phosphorus in their waste. Plants absorb phosphorus through their roots and incorporate the phosphorus into their tissues. Animals absorb the phosphorus when they eat the plants. When the animals die, the phosphorus returns to the environment through decomposition.

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Cycles in the Earth System, continued The Water Cycle The movement of water from the atmosphere to Earth’s surface and back to the atmosphere is called the water cycle. In the water cycle, water changes from liquid water to water vapor through the energy transfers involved in evaporation and transpiration. During these processes, water absorbs heat and changes into a gaseous state. When the water loses energy, it condenses to form water droplets, such as those that form clouds and fall to Earth’s surface as precipitation.

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Energy in the Earth System Chapter 2 Humans and the Earth System All natural cycles can be altered by human activities. The carbon cycle is affected when humans use fossil fuels. The nitrogen and phosphorus cycles are affected by agriculture. Humans must be careful to moderate their influences on natural systems.