Vulcanism

Vulcanism, named for the ancient Roman god Vulcan, is defined as the movement of molten rock meterials from the interior of the earth towards the surface. Vulcanism may occur in either an explosiveor quiescent manner. The island volcano of Vulcan in the Mediterranean has helped to characterize the volcanic mountain form. Such activity is called extrusive vulcanism.

similary, magma (moltenrock) may never reach the surface and may solidify within the earth´s crust. this type of volcanism is known as intrusive vulcanism. Evidence of both types of activity is characteristic of volcanicregions. Both provide rock types and landforms that react in their own unique ways to agencies of weathering and erosion, which begin their inexorable attack as soon as the rock and initial landform areexposed.
Volcanoes vary significantly in type from place to place depending on how they are formed. For example, volcanoes that are made up of repeated quiescent flows of lava, and are characterized byrelatively gentle slopes, are termed shield volcanoes. Many of the Hawaiian volcanoes, like Kilauea, Mauna Loa, and Mauna Kea are of this type. Those that are made up of alternate layers of ash andlava, and possess a more nearly conical or prototypical volcanic form, are called composite volcanoes. Composite volcanoes that have a solidified intrusive plug at their core are termed plug domevolcanoes. Those that are built almost entirely of ash (which usually stands in a high angle of repose) are known as cinder cones. Paricutin, in Mexico, typifies the cinder cone type.
Some of the mostsymmetrical volcanic forms are composite types. This extraordinary symmetry is exhibited by volcanoes like Mount Fuji in Japan and Mount Mayon in the Philippines. It is said of Mount Mayon that it is themost perfect volcanic cone in the world. If symmetry of slope is considered, that may be the case, but Fuji with a snow-capped summit has a kind of ethereal beauty about it. Mayon is not high enough...