HKDSE Geography/M1/Intrusive Vulcanicity

Intrusive vulcanicity occurs when the magma enters and solidifies in lines of weakness or chambers in the earth's crust.

Process

 * 1) The magma is under great pressure.
 * 2) Plate movements and tectonic processes produce lines of weakness in the crust.
 * 3) The lines of weakness extend downwards and to the magma chamber below.
 * 4) The magma pressure is released.
 * 5) Magma and gases in the mantle rise along the cracks.
 * 6) They intrude into and solidify in chambers the earth's crust (intrusive vulcanicity).

Associated Landforms
Refer to the diagram and table below. The features on the left part of the diagram are landforms formed by intrusive vulcanicity.



Note: The precise definition of bedding planes will be discussed in the Dynamic Earth elective. For now, bedding planes are rock layers.

Intrusive rocks
Intrusive rocks are formed by intrusive vulcanicity. When magma cools and solidifies in the earth's crust, rocks with large crystals are formed. If it was formed very deep in the earth's crust, it is a plutonic rock. They can be exposed onto the earth's surface after denudation. Intrusive rocks are a subset of igneous rocks, which include rocks formed from intrusive and extrusive vulcanicity. These will be covered in great detail in the Dynamic Earth elective.