Forces Shaping Earth

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Forces Shaping Earth

• Notes
• Mrs. Seay
• 6th Grade Science

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• Geologists use earthquakes and surface rocks to
  indirectly observe Earths interior

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• 1. Seismic waves change speed and direction
  depending on the density and material they travel
  through.

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• 2. Forces bring rocks formed deep within Earth
  to the surface.

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• 3. Evidence suggests that Earth is formed of
  different materials in layers.

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• B. Earth has four layers.

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• Inner coredense iron core very hot and dense.

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• Outer coremolten metal above the inner core

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• Solid layer that flows slowly like putty is the
  mantle.

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• Outermost layer is the crust.

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• C. Earths structuretheories based on physical
  properties of density, temperature, and pressure
  that change with depth.

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• Earths moving plates are sections of the
  lithosphere, the rigid upper part of the mantle
  and crust.

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• Plate boundaries are edges where plates meet.

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• Tension can pull plates apart, resulting in new
  lithosphere forming in the gaps.

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• Colliding plates could cause mountains to form as
  rock crumbles and folds.

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• Subduction occurs when a denser plate sinks
  underneath a less dense plate.

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• Shearing causes faults and earthquakes as two
  plates slide past each other.

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• Plate movement theoryconvection in the mantle
  circulates material and moves plates.

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• Ridge-push at mid ocean ridges causes plates to
  slide down the slope.

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• Slab-pull happens as plates move away from
  mid-ocean ridges and become denser.

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• Mountains form in different ways.

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• Fault-block mountains form from huge tilted
  blocks of rock separated from surrounding rock by
  large faults.

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• Folded mountains form by compression forces
  folding rock layers.

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• Upwarped mountainsforces push up Earths crust
  and allow the sedimentary rock to erode, leaving
  igneous or metamorphic rock.

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• Over time, layers of lava can form a cone-shaped
  volcanic mountain.

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• Hot spots formed by plumes of magma in the mantle
  can cause underwater volcanic mountains.

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• Isostacy principle in dicates Earths crust and
  lithosphere float on the upper mantle.

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• Earths crust is thicker under mountains.

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• When mountains erode, the crust rises because the
  weight has been removed.