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SEEC Ecuador 2010 Presentation by:Mary D. CurtisBrittany Heller

• Also known as composite cones, • Are the most deadly of the volcano types. • Lower slopes are gentle• Rise steeply near the summit • Summit area typically contains a surprisingly small summit crater.

• Shapes are more variable, primarily because of wide variations in eruptive style and composition.

• Some may contain several eruptive centers, a caldera, or perhaps an amphitheater as the result of a lateral blast (e.g., Mt. St. Helens).

The eruptive history of most stratovolcanoes are often associated with deadly pyroclastic flows composed of hot volcanic fragments and toxic gases that advance down slopes at hurricane-force speeds.

They erupt infrequently, with typical repose intervals of hundreds of years between eruptions. Most active stratovolcanoes worldwide appear to be < 100,000 years old, although some may be more than 1 million years old.

TungurahuaStratovolcano in Ecuador

Typically, as shown in the image to the right, stratovolcanoes have a layered or stratified appearance with alternating lava flows, pyroclastic flows, volcanic mudflows (lahars), and/or debris flows. The compositional spectrum of these rock types may vary.

Typically form at convergent plate margins, in a subduction zone.

Can be located anywhere.Abundant along the Ring of Fire - the rim of the Pacific Ocean

In the Americas, the Ring of Fire includes stratovolcanoes forming the Aleutian islands in Alaska, the crest of the Cascade Mountains in the Pacific Northwest, and the high peaks of the Andes Mountains in South America. A satellite view of three stratovolcanoes from the Andes is shown here: