Transcript File - AstroGeology

Mt Rainier from the west. Stan Shebs. 11/13/13 (http://commons.wikimedia.org/wiki/File:Mount_Rainier_from_west.jpg)
 Stratovolcano, otherwise known as composite cones,
are the most picturesque and dangerous of
volcanoes. These dangerous structures have been
the cause of much death and loss of property. Many
of these volcanoes lie near well populated areas
making understanding them very important.
Mt.fuji from R469. Yuno-yuno, 23 May 2007
(http://commons.wikimedia.org/wiki/File:Mt_fuji%28R469_Yuno%29.jpg
 Stratovolcano are characterized by shallow slopes that
increase in angle as you approach the summit.
 These volcanoes are dotted with many secondary vents
along there surface
 In general, stratovolcanoes have small summit craters.
 Stratovolcanoes may differ in shape dramatically due to
composition or violent past eruptions i.e. Mt. St. Helens
http://www.decadevol
cano.net/photos/keyw
ords/stratovolcano.ht
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 Stratovolcano take tens of thousands to hundreds of thousands of
years to form.
 Most currently active volcanoes of this type are less than 100,000
years old, but some, such as Mount Rainier are possibly over a
million
 These volcanoes alternate between eruptions of pyroclastic
material and lava flows. This variation allows the volcano to grow to
tremendous heights.
 The materials extruded from these volcanoes can range from fine
grained basaltic flows to coarse grained rhyolitic flows in the same
volcano. However, the most common composition is andesite.
http://www.geology.sdsu.ed
u/how_volcanoes_work/Thu
mblinks/volcschema_page.h
tml
 Stratovolcano typically form at convergent boundaries, where
two plates meet and one is subducted beneath the other.
 Subduction zones are found in abundance along the rim of the
pacific ocean in a region known as ‘the Ring of Fire’
 Mt. St. Helens, Mt. Rainier, Mt. Hood, the Aleutian islands, and the Andes
mountain range in South America are all stratovolcano ranges located along
the ring of fire.
11 February 2009,
http://upload.wikimedia.org/wi
kipedia/commons/5/52/Pacific
_Ring_of_Fire.svg
 On March 16, 1980 earthquakes began to rumble beneath the
surface of Mt. St. Helens. A bulge began to form indicating
activity in the volcano.
 On March 18, following an earthquake, the volcanos summit
and bulge slid away, causing the largest landslide in recorded
history, and depressurizing the magma system within.
 The subsequent explosion shot ash and debris to the north at
300 mph.
 An hour later massive pyroclastic flows flowed five miles to the
north.
 The resulting cloud of ash spread far eastward and left
Spokane, Washington in complete darkness 250 miles away.
Lyn Topinka, 19 May 1982 (http://en.wikipedia.org/wiki/File:MSH82_st_helens_plume_from_harrys_ridge_05-19-82.jpg)
 Mount Vesuvius is the only active volcano in mainland Europe
 Vesuvius is “fueled” by the subduction of the African plate
beneath the Adriatic Sea.
 Vesuvius is most commonly known for its 79 A.D. eruption that
destroyed Pompeii and Herculaneum.
 The eruption of Vesuvius in 79 A.D. is estimated to have killed
16,000 people, burying them in hot ash.
 Mt. Vesuvius last erupted in 1944, during world war II, causing
problems for the newly arrived allied forces.
http://blog.otel.com/top-tenfamous-volcanoes/mt-vesuvius/
 Krakatoa is a stratovolcano located in the Indonesian island arc
 In it’s historic 1883 eruption 36,000 people are estimated to have
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been killed, due to thermal injury from the blast or from the
tsunamis that occurred when the volcano collapsed into the
caldera.
The volcanic activity of Krakatoa is caused by the subduction of the
Indo-Australian tectonic plate into the Eurasian plate.
The eruption could be heard as far away as Perth, Australia, more
than 2,500 miles away.
The force of the eruption is estimated at 2,000 megatons. (10,000
times larger than the explosion at Hiroshima)
The resulting cloud of ash reduced the worlds temperature by
around 1.2 degrees farenheight for the next five years.
Nearby mount Tambora had an even larger explosion that reduced
global temperatures by 5 degrees
 Mt. Rainier is known as Americas most dangerous volcano
 Rainier’s danger comes not from a possible eruption, but rather
from a hollow interior
 5,600 years ago, the top portion of Mt. Rainier collapsed into a
massive lahar, flowing over 100 miles to Puget Sound.
 Around 150,000 people live atop these ancient mud flows, and
many more live in the cities of Seattle and Tacoma directly
adjacent to the volcano.
 The people in the area surrounding Mt. Rainier have prepared
evacuation routes and watch the mountain closely, waiting for
the possible collapse.
 . N.p.. Web. 13 Nov 2013. <http://basicplanet.com/stratovolcano/>.
 Camp, V.. N.p.. Web. 13 Nov 2013.
<http://www.geology.sdsu.edu/how_volcanoes_work/stratovolc_page
.html>.
 Brantley, S., and B. Myers. N.p.. Web. 13 Nov 2013.
<http://pubs.usgs.gov/fs/2000/fs036-00/>.
 Ball, J.. N.p.. Web. 13 Nov 2013. <http://geology.com/volcanoes/vesuvius/>.
 Fink, M.. N.p.. Web. 13 Nov 2013.
<http://www.pbs.org/wnet/savageplanet/01volcano/03/indexmid.html>.