South Sister

3 Pages 734 Words

SOUTH SISTER

Redmond Oregon is where my brother lives. The town is located near the Oregon’s cascade range where there are several large snow covered volcanoes. I well be focusing on the south sister, which is the youngest and highest of a trio of closely grouped volcanoes called the three sisters. The south sister could be a threat to my brother because he lives only a few miles away, and according to sources the volcano may be coming to life.
South sister is a composite volcano 10,358 feet high, it cone is comprised of adesite, dacite and rhyodacite, and is relatively young compared to its neighboring volcanoes. The latest eruptions on south sister occurred in two closely spaced episodes about 200 years ago. The eruption was a modest eruption producing small pyroclastic flows and tephra. But preceding that, similar style eruptions up to ten times larger occurred during and just before the last ice age 30,000-15,000 years ago. These larger eruptions produced pyroclastic flows that covered over a very large area from sisters to bend(see map) and tephra fallout deposits as thick as 42 feet. Such an eruption would be catastrophic today due to the mass population located near the base of the volcano. The wilderness around the volcano is becoming increasingly populated. Some 110,000 people live in areas that were criss-crossed by rivers of hot ash and rubble in previous Sister eruptions.

According to (Ann Carns, 2002) the south sister volcano is beginning to show signs of activity after several thousand years of slumber. About a year ago scientist at the (USGS) detected a bulge in the earths crust near the base of the south sister. Using radar data they found that the ground of the south sister swelled about 4 in since 1996. This swelling has continued at a rate of about 1 in per year. In addition to the swelling small amounts of gas (chloride and sulfate) from molten rock are showing up in some spring waters around the bulge...