CRCT Information

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CRCT Information
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Erosion

• Erosion is the process by which soil and
  weathered rock particles (sediment - gravel,
  sand, silt, and clay) are transported, or moved
  from one place to another.

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The agents of erosion are

• Running water
• Wind
• Ice (glaciers)
• Waves
• Gravity (mass wasting)

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Creep

• A SLOW downhill movement of soil and regolith
  (The layer of loose rock resting on bedrock).
  Creep results in tree trunks that are curved at
  the base, tilted utility poles, fence posts, and
  tombstones, and causes retaining walls to be
  broken or overturned.

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Ice-covered Cirques,

• Transantarctic Mountains, AntarcticaIce moves
  off the flat uplands into the cirques
  (bowl-shaped basins resulting from glacial
  erosion).

cirques
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Plucking

• occurs when glacial ice melts and the water
  flows down into cracks in rocks, refreezes, and
  fractures the rock into pieces.

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Loess Deposits

• Many farmlands of Midwestern United States are on
  fertile soil that developed from loess deposits.
  

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• Layers of fine sand and silt deposited by the
  wind form loess deposits. Windblown silt from the
  Pleistocene glaciations formed thick loess
  deposits in the central parts of the Mississippi
  River Valley. They form very fertile soils.

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Sand Dunes

• Forms when sediments are blown against an
  obstacle and settle behind it.

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Alluvial Fan

• Form when river waters empty from a mountain out
  onto a flat open plain.

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The amount of runoff

• Water that doesnt soak into the ground or
  evaporate.
  
• Determined by
• The amount of vegetation
• The amount of rain
• The slope of the land

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Longshore Currents -

• Carry sand down beaches to form features such as
  baymouth bars (Baymouth bar - A linear sand
  deposit that is continuous across the mouth of a
  bay) and spits.
• Spit along California coast.

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Mississippi River Drainage Basin

• Is the largest drainage basin in the United
  States.

Currently active delta front of the Mississippi
River
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Earthquakes

• When the force on rock is great enough, they
  break, producing vibrations.
  

Blue primary waves followed by red secondary
waves move outward in concentric circles from th
e epicenter of an earthquake off British Columbi
a and Washington State.
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Focus

• The point in Earths interior where the energy
  release of an earthquake occurs is the focus.

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Shear

• The force that causes plates to move sideways
  past each other.
  
• Occur at transform boundaries.
• The fault is called a strike-slip fault.

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Normal Faults

• Caused by tensional forces.
• Occur along divergent boundaries.

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Reverse Fault

• In a reverse fault, the block above the fault
  moves up relative to the block below the fault.
  This fault motion is caused by compressional
  forces and results in shortening.

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View Different Types of Faults
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Seismograph

• Earthquakes generate seismic waves which can be
  detected with a sensitive instrument called a
  seismograph.

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Richter scale

• is a standard scale used to compare earthquakes.

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It is a logarithmic scale

• meaning that the numbers on the scale measure
  factors of 10. So, for example, an earthquake
  that measures 4.0 on the Richter scale is 10
  times larger than one that measures 3.0. On the
  Richter scale, anything below 2.0 is undetectable
  to a normal person and is called a microquake.

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seismic waves.

• Energy is released which has been building up
  over many years. This released energy travels
  through rocks in the form of vibrations called
  seismic waves.

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Seismic Waves

• Speed up when they reach the bottom of the crust.

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Primary Waves (P-Waves)

• The first waves to reach a seismograph after an
  earthquake.
  
• They slow down when they hit the liquid outer
  core.

Primary waves are compression waves.
They push and pull the rocks of the earth's
surface.
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Secondary Waves (S-Waves)

• Secondary waves move through solid rock only.
  These shear waves move the earth's surface side
  to side.

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Surface Waves

• The most destructive seismic waves.

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Love Waves (L-waves)

• Love waves move along the surface of the earth
  and cause it to move up and down like something
  bobbing on the surface of the ocean.

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Rayleigh Waves

• A Rayleigh wave rolls along the ground just like
  a wave rolls across a lake or an ocean.
  
• Most of the shaking felt from an earthquake is
  due to the Rayleigh wave.

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Volcanoes
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Three Ways Volcanoes Form

• Subduction zones (Convergent Plate Boundaries)
• Mid-ocean ridges (Divergent Plate Boundaries)
• A hot spot. (Areas of Earths mantle and core
  which are believed to be hot)

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Hot Spot

• A hot spot occurs because of the intense heat of
  the outer core. This heat radiates through the
  mantle bringing hot solid rock upward to the hot
  spot. These areas of rising solid rock are called
  mantle plumes. Because of lower pressure in the
  upper region of the mantle the rock begins to
  melt. This forms magma which rises inch by inch
  until it reaches the surface forming a volcano.

More information
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Composite Volcanoes

• Composite volcanoes are constructed from multiple
  eruptions
  
• Andesite magma, the most common but not the only
  magma type forming composite cones, produces lava
  more brittle than basaltic lava.
  
• There are numerous composite volcano chains on
  earth, notably around the Pacific rim, known as
  the "Rim of Fire".

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Composite Volcano
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Dikes

• Dikes are formed when magma enters a vertical
  crack between rock layers and hardens.

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Batholith

• A batholith is created when magma cools
  underground before reaching the surface.
  
• Large body of igneous rock formed beneath the
  Earth's surface by the intrusion and
  solidification of magma.
  
• Most of the rock in Yosemite National Park is
  exposed batholith.

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Crater

• The steep-walled depression around a volcanoes
  vent is a crater.

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Caldera

• If after an eruption, the tip of a volcano
  collapses down, a caldera is formed.
  
• A caldera is a very large crater.

caldera
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Islands

• Some are formed when lava flows from rifts in the
  seafloor and builds up high enough to break the
  oceans surface.

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Shield Volcano

• Quiet eruptions of basaltic lava spread out in
  flat layers.
  
• The Hawaiian Islands are examples of Shield
  Volcanoes.

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Cinder Cone Volcano

• Cinder cone volcanoes are the most common kind of
  volcanoes. They are steep sided cones of basaltic
  fragments and are smaller and simpler than
  composite volcanoes.
• Explosive eruptions
• Bits of rock or solidified lava dropped from the
  air are called tephra.
  
• A great example of a cinder cone is Paricutin in
  Mexico.
  
• More information

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Water Vapor and Gases

• Are a factor that determines whether a volcanic
  eruption will be quiet or explosive.

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Mt. Kilauea in Hawaii

• Basaltic Magma produces nonexplosive eruptions.
• In 1990, lava from Kilauea covered most of a town
  in Hawaii.
  
• Video View
• Questions and Answers

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Soufriere Hills in Montserrat

• Erupted in 1995
• Formed when ocean floor of the North American
  Plate and the South American Plate partially
  melted as it slid beneath the Caribbean Plate.
  
• Resulted in
• Ash
• Heat
• Acid Rain