4.2The Earth<br />
Terrestrial composition<br />The four terrestrial planets all have similar internal features:<br />Dense, metallic core<br...
Four Stages of planetary development<br />Earth is believed to have formed about 4.6 BYA from the solar nebula.<br />Along...
Four stages ofplanetary development<br />Recall, differentiation, the separation of material according to density, is beli...
Four stages ofplanetary development<br />The heavy bombardment about occurred about 4 BYA and made craters on Earth and ot...
Tectonic plates<br />Earth’s crust is composed into several distinct pieces, which are in constant motion with respect to ...
Tectonic plates<br />Where plates move toward one another, they can be pushed upward or downward  convergent plate bounda...
Hot spots  result of magma penetration through holes in tectonic plates (Hawaii formation)<br />
About 1 BYA, the supercontinent Rodinia, meaning “motherland”, existed.<br />Most landmasses were gathered south of the eq...
About 450 MYA, after Rodinia broke up, Earth’s continents were separated as they are today.<br />The Supercontinent Cycle<...
The continents had joined back together around 200 MYA  in the supercontinent Pangaea, meaning  “all Earth”.<br />Certain ...
When Pangaea split apart, it eventually separated into a northern piece (Laurasia) and a southern piece (Gondwanaland) aro...
About 50 MYA, the continents continued their separation, resembling their current-day locations.<br />India collided with ...
Believed if plate movements continue at current rates, in 150 million years, Africa will collide with Eurasia, closing off...
A new supercontinent, Pangaea Ultima, will form in approximately 250 million years.<br />The Supercontinent Cycle<br />
History of geologic activity<br />Surface formations visible today have emerged only very recently compared to the age of ...
Earth’s interior<br />High temperature and tremendous pressure in Earth’s interior make any direct exploration impossible....
Earth’s interior<br />Two main types of seismic waves:<br />Body – seismic waves traveling through the body of a medium (f...
P Waves<br />Body waves traveling through solids and liquids are called P waves.<br />“Primary” waves<br />“Pressure” wave...
P Waves<br />
S Waves<br />Body waves traveling through only solids are called S waves.<br />“Secondary” Waves<br />“Shear” Waves<br />S...
Rayleigh Waves & Love Waves <br />Rayleigh wavesare surface waves causing the ground to move with an elliptical, rolling m...
seismology<br />The P and S waves (body) caused by an earthquake do not travel in straight lines or at constant speeds wit...
Earth’s structure<br />Solid crust<br />Solid mantle<br />Liquid core<br />Solid inner core<br />Earth’s interior gets hot...
Earth’s magnetic field<br />Earth’s core consists mainly of Iron (Fe) and Nickel (Ni)<br />Both have high electrical condu...
Earth’s magnetic field<br />Earth’s magnetic field protects it from the solar wind (ionized gases).<br />The surface of th...
Earth’s magnetic field<br />As high-energy particles leak into the lower magnetosphere, they excite molecules near the Ear...
Earth’s atmosphere<br />Earth once had a primeval atmospherecomposed of gases captured from the solar nebula during the fo...
Earth’s atmosphere<br />The ozone layerexists in the second layer of Earth’s atmosphere, the stratosphere.<br />Composed o...
Greenhouse effect<br />Earth’s surface is heated by radiation from the Sun.<br />Heat energy is re-radiated from Earth’s s...
Human effects<br />The Greenhouse Effect occurs naturally an is essential to maintain comfortable temperatures on Earth.<b...
Human effects<br />The amount of warming to expect in the future is difficult to predict because Earth’s climate is critic...
Human effects<br />Chlorofluorocarbons (CFC’s), used in industrial processes, refrigeration, and air conditioning destroy ...
AST 4.2 PPT
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AST 4.2 PPT

  1. 1. 4.2The Earth<br />
  2. 2. Terrestrial composition<br />The four terrestrial planets all have similar internal features:<br />Dense, metallic core<br />Less dense, liquid-like mantle<br />Low-density, solid crust<br />
  3. 3.
  4. 4. Four Stages of planetary development<br />Earth is believed to have formed about 4.6 BYA from the solar nebula.<br />Along with the other terrestrial planets, Earth passed through 4 developmental stages:<br />Differentiation<br />Cratering<br />Flooding<br />Slow Surface Evolution<br />
  5. 5. Four stages ofplanetary development<br />Recall, differentiation, the separation of material according to density, is believed to have occurred due to melting of Earth’s interior.<br />Heat generated from radioactive decay and energy released from in-falling matter.<br />
  6. 6. Four stages ofplanetary development<br />The heavy bombardment about occurred about 4 BYA and made craters on Earth and other planets.<br />When the environment cooled, water fell as rain and flooded the deep basins of Earth.<br />Continuing surface evolution over the past 3.5 billion years has constantly re-shaped the surface of the Earth (geologic processes along with weathering/erosion).<br />
  7. 7. Tectonic plates<br />Earth’s crust is composed into several distinct pieces, which are in constant motion with respect to each other and this process is known as plate tectonics.<br />Evidence of this is found on the ocean floor …<br />… and in geologically active regions across the Pacific.<br />
  8. 8. Tectonic plates<br />Where plates move toward one another, they can be pushed upward or downward  convergent plate boundary.<br />Formation of mountain ranges, presence of volcanic activity and/or earthquakes.<br />Where plates move away from each other, magma can rise up, producing volcanism  divergent plate boundary.<br />
  9. 9. Hot spots  result of magma penetration through holes in tectonic plates (Hawaii formation)<br />
  10. 10.
  11. 11. About 1 BYA, the supercontinent Rodinia, meaning “motherland”, existed.<br />Most landmasses were gathered south of the equator.<br />The Supercontinent Cycle<br />
  12. 12. About 450 MYA, after Rodinia broke up, Earth’s continents were separated as they are today.<br />The Supercontinent Cycle<br />
  13. 13. The continents had joined back together around 200 MYA in the supercontinent Pangaea, meaning “all Earth”.<br />Certain mountain ranges formed, including the Appalachians.<br />The Supercontinent Cycle<br />
  14. 14. When Pangaea split apart, it eventually separated into a northern piece (Laurasia) and a southern piece (Gondwanaland) around 150 MYA.<br />The Supercontinent Cycle<br />
  15. 15. About 50 MYA, the continents continued their separation, resembling their current-day locations.<br />India collided with Eurasia  Himalaya Mountain formation.<br />The Supercontinent Cycle<br />
  16. 16. Believed if plate movements continue at current rates, in 150 million years, Africa will collide with Eurasia, closing off Mediterranean Sea.<br />New subduction zones will form, closing off the Atlantic as well.<br />The Supercontinent Cycle<br />
  17. 17. A new supercontinent, Pangaea Ultima, will form in approximately 250 million years.<br />The Supercontinent Cycle<br />
  18. 18. History of geologic activity<br />Surface formations visible today have emerged only very recently compared to the age of Earth.<br />
  19. 19. Earth’s interior<br />High temperature and tremendous pressure in Earth’s interior make any direct exploration impossible.<br />Exploration possible because earthquakes produce vibrations called seismic waves, traveling through the interior of the Earth.<br />Register on sensitive detectors called seismographs all over the world.<br />
  20. 20. Earth’s interior<br />Two main types of seismic waves:<br />Body – seismic waves traveling through the body of a medium (fastest-moving seismic wave category).<br />P waves<br />S waves<br />Surface – seismic waves traveling along the surface of a body rather than through the middle of it (slowest-moving seismic wave category; most destructive).<br />Rayleigh waves<br />Love waves<br />
  21. 21. P Waves<br />Body waves traveling through solids and liquids are called P waves.<br />“Primary” waves<br />“Pressure” waves<br />Fastest moving seismic wave.<br />Avg. speed in crust = 6.1 km/s<br />Particles of rock move in a back-and-forth direction.<br />
  22. 22. P Waves<br />
  23. 23. S Waves<br />Body waves traveling through only solids are called S waves.<br />“Secondary” Waves<br />“Shear” Waves<br />Second fastest seismic wave.<br />Avg. speed in crust = 4.1 km/s<br />Particles of rock move in an side-to-side direction.<br />
  24. 24. Rayleigh Waves & Love Waves <br />Rayleigh wavesare surface waves causing the ground to move with an elliptical, rolling motion.<br />Love wavesare surface waves causing the ground to move with a side to side motion perpendicular to the direction of the traveling wave.<br />
  25. 25.
  26. 26. seismology<br />The P and S waves (body) caused by an earthquake do not travel in straight lines or at constant speeds within the Earth.<br />May reflect off boundaries between the layers of different density, or they may be refracted as hey pass through a boundary.<br />Such information can be analyzed to infer the structure of Earth’s interior.<br />
  27. 27. Earth’s structure<br />Solid crust<br />Solid mantle<br />Liquid core<br />Solid inner core<br />Earth’s interior gets hotter towards the center.<br />Earth’s core is as hot as the Sun’s surface; metals are liquid.<br />Melting point = temperature at which an element melts<br />Melting point increases with increasing pressure towards the center<br />- Reason inner core becomes solid<br />
  28. 28. Earth’s magnetic field<br />Earth’s core consists mainly of Iron (Fe) and Nickel (Ni)<br />Both have high electrical conductivity.<br />The rotation of the convecting, conducting liquid (outer core) generates Earth’s magnetic field in a process called the dynamo effect.<br />Same process that generates the solar magnetic field in the convective layers of the Sun.<br />
  29. 29. Earth’s magnetic field<br />Earth’s magnetic field protects it from the solar wind (ionized gases).<br />The surface of the magnetic field where the solar wind is first deflected is called the bow shock.<br />The region where Earth’s magnetic field dominates is called the magnetosphere.<br />High-energy particles from the solar wind leak into the magnetosphere and become trapped within Earth’s magnetic field and produce belts of radiation known as the Van Allen belts.<br />
  30. 30. Earth’s magnetic field<br />As high-energy particles leak into the lower magnetosphere, they excite molecules near the Earth’s magnetic poles, causing the auroras.<br />
  31. 31. Earth’s atmosphere<br />Earth once had a primeval atmospherecomposed of gases captured from the solar nebula during the formation of Earth (H, He, CH4).<br />Composition was severely altered, eventually led to a secondary atmosphere through 2 main processes:<br />Outgassing: release of gases in Earth’s interior through volcanism. During a volcanic eruption, 50-80% of the gas released is water vapor. The rest is CO2, nitrogen, and small amounts of sulfur gases.<br />Later bombardment with icy meteoroids and comets.<br />
  32. 32.
  33. 33. Earth’s atmosphere<br />The ozone layerexists in the second layer of Earth’s atmosphere, the stratosphere.<br />Composed of 3 oxygen atoms linked together, O3.<br />Absorbs (is opaque to) ultraviolet radiation from the Sun, protecting life on Earth’s surface.<br />
  34. 34. Greenhouse effect<br />Earth’s surface is heated by radiation from the Sun.<br />Heat energy is re-radiated from Earth’s surface as infrared radiation.<br />CO2 makes the atmosphere less transparent to infrared radiation (more opaque).<br />Just as glass is opaque to infrared radiation in a greenhouse.<br />Thus, heat is trapped due to CO2 through a process known as the greenhouse effect.<br />
  35. 35. Human effects<br />The Greenhouse Effect occurs naturally an is essential to maintain comfortable temperatures on Earth.<br />However, human activity may be increasing the concentration of greenhouse gases through CO2 emissions (cars and industrial plants) and deforestation through what is known as global warming.<br />
  36. 36. Human effects<br />The amount of warming to expect in the future is difficult to predict because Earth’s climate is critically sensitive to a number of different factors, not just the abundance of greenhouse gases.<br />For example, a planet’s albedo is the fraction of sunlight hitting it that gets reflected away.<br />Albedo of 1 = WHITE<br />Albedo of 0 = BLACK<br />Earth’s albedo is about 0.39<br />39% of sunlight hitting it reflects back to space.<br />
  37. 37. Human effects<br />Chlorofluorocarbons (CFC’s), used in industrial processes, refrigeration, and air conditioning destroy the ozone layer (which absorbs UV radiation).<br />Destruction of the ozone layer proven  ozone hole over Antarctica.<br />
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