THREE PRIMARY TYPES OF VOLCANOES

Mauna Loa, Hawaii, is an excellent example of a shield volcano.

(1) Shield volcanoes, the largest of the three types, are gently sloping and built almost entirely of low viscosity basaltic lava flows. The eruptions are generally nonexplosive due to the low silica content. Shield volcanoes are typified by those on the Hawaiian and Galapagos Islands and on Iceland, although Iceland also caontains other types of voclanoes.. Numerous small shield volcanoes are typical throughout the eastern Snake River Plain in Idaho, USA. Examples include the Wapi lava field and Hells Half Acre.

 

Mt. Shasta is a stratovolcano or Composite Volcano.

(2)  Composite volcanoes are the most beautiful - - - and ! - - - the most deadly of the volcano types, at least in Holocene time.
Their lovely steep-sided, symmetrical cone shapes are built up by eruptions of intermediate viscosity andesitic lava and explosive tephra.
Examples of composite volcanoes, also called stratovolcanoes, are Mount Shasta in California, Mount St. Helens and Mount Rainier in Washington state, and Mount Fuji in Japan.
East Butte, on the eastern Snake River Plain in Southern Idaho (USA), is a rhyolitic volcanic dome.
Photo by Scott Hughes

(3) Volcanic Domes comprise the third primary type of volcano. They are formed by highly viscous rhyolitic magma (approximately 70% silica). Volcanic domes are typically small. Some are subject to explosive blowouts during dome building processes. Domes commonly occur adjacent to or within craters of composite volcanoes. Other domes begin as shallow laccolithic intrusions that grow and expand beyond subsurface confinement.