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The Geosphere


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  • 1. THE GEOSPHERE Chapter 3, Section 1
  • 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. The Structure and Composition of the Earth
  • 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. 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. 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. 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. 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. Core  Radius = 3,400 km  Mostly iron but also contains some nickel.  Temperature is probably around 5,000ºC
  • 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. 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. 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. Mesosphere  Beneath the asthenosphere  2,550 km thick  Name means the “middle sphere”
  • 14. Outer Core  Beneath the mesosphere  2,200 km thick  Made of liquid nickel and iron
  • 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. 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. Plate Tectonics
  • 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. 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. Earthquakes
  • 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. 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. 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. Volcanoes
  • 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. 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. Sometime before May 18, 1980 Mt. St. Helens (Washington) Before…
  • 28. May 18, 1980 Mt. St. Helens, During…
  • 29. May 18, 1980 Mt. St. Helens, During…
  • 30. Mt. St. Helens, During… Mt. St. Helens, During…
  • 31. May 19, 1982 Mt. St. Helens, 2 Years after…
  • 32. Large trees (some over 100 feet tall) flattened by the lateral blast from Mt. St. Helens. The Lateral Blast
  • 33. An Approaching Ash Cloud
  • 34. The Ash Fallout from Mt. St. Helens
  • 35. Cleaning Up the Ash
  • 36. The Before and After Before After
  • 37. The Mudflow
  • 38. Mt. St. Helens Today
  • 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. 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. Erosion
  • 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. Water Erosion  Ocean waves erode coastlines.  Rivers can carve deep gorges into the Earth.
  • 44. Water Erosion
  • 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. Wind Erosion