Posted By SinontukMukzmo on February 5, 2012
A shield volcano forms when magma moves slowly, creating a large, gently sloping volcanic cone. A well known example of a shield volcano is Mauna Loa in Hawaii. The lava emitted by a shield volcano has a low viscosity, so it pours out readily, and these volcanoes may form slowly over a long period of time, with fresh lava deposits layering on top of older ones. Volcanic cones of this type have a very low profile, looking rather like a giant warrior’s shield lying on the ground.
Volcanic cones of the spatter type are formed by thick lava and magma which erupts violently around a vent, creating gobs of material which fuse together as the lava cools. Spatter cones are characterized by very irregular surfaces, caused by large chunks of lava and other material. Fans of the Lord of the Rings series may be familiar with spatter cones, as Mount Doom is a classic example.
Composite volcanic cones are caused by alternating layers of magma, rock fragments, and ash. They often erupt violently and unpredictably; Vesuvius, Mount St. Helens, and Mt. Shasta are all examples of composite cones. Composite cones can also cause lahars, mudflows of volcanic ash which can be quite devastating.
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