Intrusive Activity

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Intrusive Activity

• Chapter 18.2

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• Molten Magma is less dense than surrounding
  rocks.
• This forces magma to move upward intrude into,
  the overlying crust.

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Intrusive Activity
A. Magma can force the overlying rock apart and
enter the newly formed fissures. B. Magma can
also cause blocks of rock to break off and sink
into the magma, where the rocks may eventually
melt. C. Magma can melt the rock into which it
intrudes.
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Plutons

• Plutons are intrusive igneous rock bodies that
  can be exposed at Earths surface as a result of
  uplift and erosion and are classified based on
  their size, shape, and relationship to
  surrounding rocks.

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Plutons
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Batholiths

• Batholiths, the largest plutons, are irregularly
  shaped masses of coarse-grained igneous rocks
  covering at least 100 km2 and take millions of
  years to form.

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Batholiths
The Sierra Nevada and San Gabriel mountains are
large Batholiths
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Stocks

• Stocks are irregularly shaped plutons that are
  similar to batholiths but smaller in size.

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Laccoliths

• A laccolith is a mushroom-shaped pluton with a
  round top and flat bottom resulting from a Magma
  intrusion into parallel rock layers close to
  Earths surface.

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Laccoliths
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Sills

• A sill is a pluton, ranging from only a few
  centimeters to hundreds of meters in thickness,
  that forms when magma intrudes parallel to layers
  of rock.

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Sills

• Glacier Park in PreCambrian rocks

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Dikes

• A dike is a pluton, ranging from a few
  centimeters to several meters wide and up to tens
  of kilometers long, that cuts across preexisting
  rocks.

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Dikes
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Dikes

• Sierra Nevada

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Dike Near Shiprock NM
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Dike Near Shiprock NM
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Dike Near Shiprock NM