Presentation on theme: "(9) Solid Earth. The student knows Earth's interior is differentiated chemically, physically, and thermally. The student is expected to: (a) evaluate heat."— Presentation transcript:
(9) Solid Earth. The student knows Earth's interior is differentiated chemically, physically, and thermally. The student is expected to: (a) evaluate heat transfer through Earth's subsystems by radiation, convection, and conduction and include its role in plate tectonics, volcanism, ocean circulation, weather, and climate; Greenhouse effect (radiation) Deep sea vs. surface currents (b) examine the chemical, physical, and thermal structure of Earth's crust, mantle, and core, Including the lithosphere and asthenosphere; Earth’s internal structure
Earth’s subsystems include: the lithosphere the atmosphere the hydrosphere the biosphere Thermal energy from the sun is transferred through each of these subsystems in three ways. Conduction Convection Radiation Contains all of the planet’s land, and rocky surfaces…which may be beneath the ocean. Contains the envelope of protective gases which surround the planet. Contains all the water on the planet, which can be solid, liquid, and gas. Contains all of the planet’s living things, animals and plants, fungi, bacteria, and protists.
Conduction is the transfer of heat energy between two objects that are in direct contact with each other. Walk on a sidewalk with bare feet in the summer and you know about conduction. Dive into a swimming pool, and you know about conduction. The better the conductor, the faster the heat energy will transfer. Objects and substances that do not make good conductors are called insulators. In the Lithosphere: In the Atmosphere: In the Hydrosphere: In the Biosphere: The conduction of heat slowly through the outer layers of the lithosphere, causes it to cool and thicken over time. The atmosphere is an EXTREMELY poor conductor of heat energy, and only the first few millimeters above the Earth’s surface are capable of it. The hydrosphere is also EXTREMELY poor at conducting heat energy, and again, only the regions close to the surface of the Earth conduct heat energy efficiently The Earth’s terrestrial surface is obviously linked to the atmosphere by conduction. Once the surface is heated by radiant energy, it can be transferred to organisms…or through simple body-to-body contact.
1.What are the four Earth subsystems we will be studying in terms of energy transfer? 2.By what three ways is thermal energy transferred? 3.If a substance is not a good conductor of thermal energy, it is called what? 4.In which subsystems is conduction most efficient? 5.How does the biosphere experience conduction? 6.In which two subsystems is conduction inefficient?
Convection is the “up and down” movement of fluids (both gases and liquids) that is caused by heat transfer. As gases and liquids are heated, they expand and rise, and become less dense. As they cool they contract, and sink…and become more dense. This rising and falling motion is called a “convection current”. In the Lithosphere: In the Atmosphere: In the Hydrosphere: In the Biosphere: As the lithosphere is the rigid, rocky, outermost portion of our solid planet, it does not convect heat energy. Only fluids transfer energy through convection. Heat gained by the lowest layer of the atmosphere from radiation or conduction is most often transferred by convection. Convective motions in the atmosphere are responsible for the redistribution of heat from the warm equatorial regions to higher latitudes and from the surface upward The biosphere is not directly affected by convection, but given the high degree of interconnection between different Earth subsystems, convection indirectly affects the biosphere in the air, and waters Energy from the Sun heats the Earth’s surfaces unevenly. As a result, convection currents develop in the oceans. These redistribute heat in oceans.
Convection occurs in Earth’s mantle, as directed by the internal heat furnace of the Earth’s interior. Remember, some of this heat energy is left-over from the accretion process. Most of it, however, is a direct result of the radioactive decay of the heavy Earth elements such as plutonium, and uranium. The thermal structure of the Earth’s interior is impressive, and at its core, the temperature is as hot as the outer surface of the Sun. Certainly, enough heat energy to drive the tectonic plates on Earth’s surface!
In the lithosphere, biosphere, and hydrosphere, radiant energy has an indirect role, as radiation moves most readily through space. This radiant energy is transferred to Earth’s surfaces, and transformed into thermal energy and chemical energy. It can either be absorbed, or re- radiated back to space. When electromagnetic energy waves move through the vacuum of space from a star, as soon as they come into contact with a planet or other object, the waves transfer the heat to that object. Our sun produces electromagnetic waves that move through space and strike the Earth (and all the objects in our Solar System). This warms the Earth. The Atmosphere The atmosphere has the capacity to accept and transmit the Sun’s radiant energy. Radiation occurs through any transparent medium (solid or fluid) but also occurs across a vacuum. We feel the warmth of the Sun on a summer day because of radiation.
7. Which two subsystems are the most efficient at convection? 8.How is the biosphere indirectly influenced by convection? 9.Label and describe the thermal structure of each of the following: 1. Crust 2. Mantle 3. Outer core 4. Inner core 10. Once the sun’s radiant energy strikes the Earth’s surface, how is it transformed? 11. % absorbed? % redirected?
The hydrologic cycle is driven by the Sun’s energy. Evaporation Condensation Precipitation Infiltration Transpiration Runoff Solar energy input dominates the surface processes (wind, weather, climate, ocean circulation, etc.) of the Earth, and because the Earth is a sphere, its input is not uniform across the planet. The concentration of solar energy depends on the angle at which the solar radiation arrives. In equatorial regions, where the sun's rays come in close to perpendicular, a maximum amount of heat is received. In polar regions, on the other hand, the sun's rays come in slanted at a shallow angle and considerably less heat is received.
12. Describe each of the following: Evaporation Condensation Precipitation Infiltration Transpiration Runoff 13. Where on Earth is the angle of insolation greatest? 14. Where on Earth is the angle of insolation least? 15. How does angle of insolation influence temperatures on the surface of the Earth?
With deep ocean currents, we see another “mock” convective current. “Mock”, because it is only indirectly driven by heat energy. This deep ocean current is more a product of density, or salt concentration. Density, however, is an indirect product of heat energy, as rainwater (due to heat energy driving the hydrologic cycle) dilutes saltwater. For this reason, ocean water closer to tropical regions is “less salty”, than ocean water near the poles. The denser something is, the faster it sinks. The cold dense ocean water in the poles, sinks along the ocean bottom in the North Atlantic, and follows this “conveyer belt” all the way to the Indian Ocean. Tropical waters are less dense, and they rise, and the water begins its trek northward along the same path. These currents regulate temperatures on the continents. Because global warming is changing the density of these polar oceans due to glacial and ice-cap melt, this current could stop. Ultimately, this could alter the temperatures over the continents by as much as 10˚C. Global warming could cause continental cooling in the Northern Hemisphere! Surface currents are driven by winds. These winds are also driven by convection currents in our atmosphere! The Trade Winds propel ocean water westward along the equator, and when it strikes a continent, it is diverted poleward. However, a narrow return flow also occurs along the equator. In mid-latitudes the currents are driven eastward by the Westerlies. The opposing wind belts cause currents in all the ocean basins to form gyres, or giant loops
16. Deep ocean currents occur due to… 17. What force drives surface currents? 18. How can global warming cause continents in the NH to cool? 19.Which oceans are saltier, and why? 20.Which oceans are less salty, and why?
Heated air at the equator rises up, and spreads north and south towards the poles. As it cools, it first sinks down in the sub-tropics, and then again in the poles, where it moves again towards the equator. It heats up again in these areas, and the convective cycle is repeated. It isn’t an accident that the Earth’s tropical zones are in the warm air near the equator. The deserts, likewise, are located in the mid-latitude zones…and the poles are perpetually cold.
Think of the Earth’s envelope of gases as being the walls of a greenhouse. The sun’s short wave ultraviolet energy easily penetrates through these gases. The Earth’s surface absorbs some, and radiates some. The Earth’s radiated energy is transformed into infrared thermal energy. This long wave infrared energy CANNOT penetrate the Earth’s envelope of gases, trapping the heat close to us. We may think that the greenhouse effect is bad, because ultimately it leads to global warming. While it is true, that greenhouse effect is one of the mechanisms that drives global warming, without greenhouse effect, our Earth would be uninhabitable! The surface of the Earth would average about -18˚C (0˚F). Millions of years ago, Mars’ atmosphere was lost, leaving it without the ability to experience greenhouse effect. The same thing would happen to Earth, were we to lose our atmosphere. We may not be AS cold as Mars, because we are much closer to the Sun…but it would still be mighty cold!
21. How do convective atmospheric currents affect biome placement on Earth? Tropics Deserts Poles 22. Radiant energy belongs to which end of the em spectrum? 23. Thermal energy belongs to which end of the em spectrum? 24. How does Greenhouse Effect affect temperatures on Earth? 25. Is the Greenhouse Effect bad? Why, or why not? 26. What happened to Mars?
The crust is the outermost layer, and is rigid and very thin compared with the other two layers. Beneath the oceans, the crust varies little in thickness, generally extending only to about 5-10 km. The main chemical composition of the Earth’s crust is: The thickness of the crust beneath continents is much more variable but averages about 30 km; under large mountain ranges, like the Alps or the Sierra Nevada, the base of the crust can be as deep as 100 km. Like the shell of an egg, the Earth's crust is brittle and can break.
Not surprisingly, the Earth's internal structure influences plate tectonics. The upper part of the mantle is cooler and more rigid than the deep mantle, and in many ways, it behaves like the overlying crust. This rigid portion of the mantle, together with the outer crust, forms a rigid layer of rock called the lithosphere. The lithosphere has been broken up into the moving plates that contain the world's continents and oceans. There are currently seven or eight major, and many minor plates. The lithospheric plates ride on the asthenosphere. These plates move in relation to one another at one of three types of plate boundaries: convergent boundaries, divergent boundaries, and transform boundaries. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries.
27. Describe differences between the Earth’s crust beneath the continents, and oceans. 28. What are the four main elements that make up the Earth’s crust? 29. What are the 8 major tectonic plates called? 30. Lithospheric plates ride on top of the ___________. 31. Describe the three types of plate boundaries. 32. What forms along these boundaries?
Below the crust is the mantle, a dense, hot layer of non-newtonian fluid rock, approximately 2,900 km thick. The mantle, which contains more iron, magnesium, and calcium than the crust, is hotter and denser because temperature and pressure inside the Earth increase with depth. If the crust is the shell of the egg, the mantle is the egg- white. Remember, it is the “fluid” nature of the rocks in the mantle, which are heated through the radioactive decay of heavy elements, that drives the convection currents that move the tectonic plates on Earth’s crust.
In keeping with the egg-analogy, unlike the yolk of an egg, however, the Earth's core is actually made up of two distinct parts: a 2,200 km-thick liquid outer core and a 1,250 km-thick solid inner core. At the center of the Earth lies the core, which is nearly twice as dense as the mantle because its composition is metallic (iron-nickel alloy) rather than stony. As the Earth rotates, the liquid outer core spins, creating the Earth's magnetic field. This field is important, because it protects Earth from dangerous solar winds and cosmic rays by deflecting them away. Liquid Solid
33. Describe the chemical nature of the mantle. 34. Describe the chemical nature of the Earth’s core. 35. Using the Earth-Egg analogy, describe how each of these parts is like an egg: Crust Mantle Core 36. How does the Earth-Egg analogy not work? 37. Why is the outer core so important to the Earth?