Mount Redoubt (Alaska)

Mount Redoubt, or Redoubt Volcano, is an active and currently erupting stratovolcano in the largely volcanic Aleutian Range of Alaska.

A stratovolcano, sometimes called a composite volcano, is a tall, conical volcano with many layers (strata) of hardened lava, tephra, and volcanic ash. Stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions. The lava that flows from stratovolcanoes tends to be viscous; it cools and hardens before spreading far. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma.

Stratovolcanoes are sometimes called composite volcanoes because of their composite layered structure built up from sequential outpourings of eruptive materials. Stratovolcanoes are one of the most common types of volcanoes.

source :
http://en.wikipedia.org/wiki/Mount_Redoubt_(Alaska)

http://en.wikipedia.org/wiki/Stratovolcano