Transcript Stratovolcanoes Powerpoint

gsc.nrcan.gc.ca
www2.jpl.nasa.gov
SEEC Ecuador 2010
Presentation by:
Mary D. Curtis
Brittany Heller
science-art.com
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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.
Tungurahua
Stratovolcano 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: