The Geosphere


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The Geosphere

  1. 1. THE GEOSPHERE Chapter 3, Section 1
  2. 2. Learning Objectives  Describe the composition and structure of the Earth.  Describe the Earth’s tectonic plates.  Explain the main cause of earthquakes and describe their effects.  Identify the relationship between volcanic eruptions and climate change.  Describe how wind and water alter the Earth’s surface.
  3. 3. The Structure and Composition of the Earth
  4. 4. The Earth as a System  The Earth consists of rock, air, water, and living things that all interact with each other.  There are four parts of the Earth  Geosphere (rock)  Atmosphere (air)  Hydrosphere (water)  Biosphere (living things)
  5. 5. Discovering Earth’s Interior  Scientists can study the interior of the Earth by using seismic waves.  Seismic waves are the waves that travel through Earth’s interior during an earthquake.  A seismic wave is altered by the nature of the material through which it travels.  Seismologists measure changes in the speed and direction of seismic waves that penetrate the interior of the planet.  This has helped seismologists to learn that Earth is made up of different layers and different substances.
  6. 6. The composition of the Earth  The Earth is made of three layers that are made of denser materials toward the center of the Earth.  The layers are determined by the chemical composition.  3 Layers:  Crust  Mantle  Core
  7. 7. Crust  Thin outer layer  Light elements  Oceanic Crust:  5 km to 8 km thick beneath ocean  Oldest is 200 million years old  Continental Crust:  20 km to 70 km thick beneath continents  Average age is 2 billion years old  Oldest is 3.7 to 4.3 billion years old
  8. 8. Mantle  64% of the mass of the Earth  2,900 km thick  500ºC to 900ºC (upper portion of mantle)  4,000ºC (near the core)  Melting mantle produces the crust
  9. 9. Core  Radius = 3,400 km  Mostly iron but also contains some nickel.  Temperature is probably around 5,000ºC
  10. 10. The Structure of the Earth  The Earth can also be divided into layers based on physical properties.  5 Layers:  Lithosphere  Asthenosphere  Mesosphere  Outer Core  Inner Core
  11. 11. Lithosphere  Most outer layer  Cool and rigid  15 km to 300 km thick  Includes the crust and uppermost part of mantle  Divided into huge pieces called tectonic plates
  12. 12. Asthenosphere  Beneath the lithosphere  Plastic, solid layer of the mantle made of rock that flows slowly. This allows the tectonic plates to move.  250 km thick
  13. 13. Mesosphere  Beneath the asthenosphere  2,550 km thick  Name means the “middle sphere”
  14. 14. Outer Core  Beneath the mesosphere  2,200 km thick  Made of liquid nickel and iron
  15. 15. Inner Core  The innermost layer of the Earth  1,228 km radius  A sphere of solid nickel and iron at the center of the Earth.
  16. 16. Plate Tectonics  The lithosphere is divided into pieces called tectonic plates.  These plates glide across the asthenosphere like ice floats across a pond.  The continents are located on tectonic plates and move around with them.  The major tectonic plates include:  Pacific  North American  South American  African  Eurasian  Antarctic
  17. 17. Plate Tectonics
  18. 18. Plate Boundaries  Much of the geologic activity at the surface of the Earth takes place at the boundaries between tectonic plates.  Plates can:  Move away from one another  Collide with one another  Slip past one another  Enormous forces are generated at tectonic plate boundaries where the crust is pulled apart, squeezed together or is constantly slipping.
  19. 19. Mountain Building  When tectonic plates collide, slip by one another, or pull apart, enormous forces causes rock to break and buckle.  Where plates collide, the crust becomes thicker and pushed up and eventually forms a mountain range.
  20. 20. Earthquakes
  21. 21. Earthquakes  A fault is a break in the Earth’s crust.  Blocks of the crust slide past each other along fault lines.  When rocks that are under stress suddenly break, a series of ground vibrations is set off.  These vibrations are known as earthquakes.  Earthquakes are occurring all the time.
  22. 22. The Richter Scale  Used by scientists to quantify the amount of energy released by an earthquake.  Magnitude - The measure of the energy released by an earthquake.  The scale goes from 1.0 to 10.0.  Each increase of magnitude by one whole number is ten times greater and releases 31.7 times more energy than the whole number below it.
  23. 23. Richter Magnitudes Description Earthquake Effects Frequency of Occurrence Less than 2.0 Micro Microearthquakes, not felt. About 8,000 per day 2.0-2.9 Minor Generally not felt, but recorded. About 1,000 per day 3.0-3.9 Often felt, but rarely causes damage. 49,000 per year (est.) 4.0-4.9 Light Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 6,200 per year (est.) 5.0-5.9 Moderate Major damage to poorly constructed buildings over small regions. Slight damage to well-designed buildings. 800 per year 6.0-6.9 Strong Can be destructive in areas up to about 160 kilometres (100 mi) across in populated areas. 120 per year 7.0-7.9 Major Can cause serious damage over larger areas. 18 per year 8.0-8.9 Great Can cause serious damage in areas several hundred miles across. 1 per year 9.0-9.9 Devastating in areas several thousand miles across. 1 per 20 years 10.0+ Epic Never recorded Extremely rare (Unknown)
  24. 24. Volcanoes
  25. 25. Volcanoes  A volcano is a mountain built from magma.  Magma – melted rock that found beneath the surface of the earth  Located near tectonic plate boundaries where plates are sliding or separating from one another.  May occur on the land or under sea.  Under sea volcanoes may eventually break through the surface as islands.
  26. 26. Volcano Eruptions  A volcano erupts when the pressure of the magma inside becomes so great that it blows open the solid surface of the volcano.  Some volcanoes have magma flowing out of them all the time so the pressure never builds up and they never erupt.
  27. 27. Sometime before May 18, 1980 Mt. St. Helens (Washington) Before…
  28. 28. May 18, 1980 Mt. St. Helens, During…
  29. 29. May 18, 1980 Mt. St. Helens, During…
  30. 30. Mt. St. Helens, During… Mt. St. Helens, During…
  31. 31. May 19, 1982 Mt. St. Helens, 2 Years after…
  32. 32. Large trees (some over 100 feet tall) flattened by the lateral blast from Mt. St. Helens. The Lateral Blast
  33. 33. An Approaching Ash Cloud
  34. 34. The Ash Fallout from Mt. St. Helens
  35. 35. Cleaning Up the Ash
  36. 36. The Before and After Before After
  37. 37. The Mudflow
  38. 38. Mt. St. Helens Today
  39. 39. Local Effects of Volcano Eruptions  Volcanic eruptions can be devastating to local economies and can cause great human loss.  Clouds of hot ash, dust, and gases can flow down the slope of a volcano at speeds up to 200 km/hour and sear everything in their path.  Volcanic ash can mix with water and produce a mudflow.  Ash that falls to the ground can cause buildings to collapse, bury crops, damage engines, and cause breathing problems.
  40. 40. Global Effects of Volcanic Eruptions  Can change Earth’s climate for several years.  Clouds of volcanic ash and sulfur-rich gases can reach the upper atmosphere.  Ash and gas spread across the planet and reduce the amount of sunlight that reaches the Earth’s surface.  Reduced sunlight can result in a decrease in the average global temperature over a period of several years.
  41. 41. Erosion
  42. 42. Erosion  The Earth’s surface is continually battered by wind and running water.  This moves rocks around and changes their appearance.  Erosion – the removal and transport of surface material.  Erosion wears down rocks and makes them smoother.
  43. 43. Water Erosion  Ocean waves erode coastlines.  Rivers can carve deep gorges into the Earth.
  44. 44. Water Erosion
  45. 45. Wind Erosion  Plant roots hold soil in place. Without plants the wind can blow soil away very quickly.  Soft rock can be carved away over time.
  46. 46. Wind Erosion