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The Geosphere

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The Geosphere The Geosphere Presentation Transcript

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