Shishaldin Volcano is a stratovolcano that is shaped as nearly a perfect cone in shape. A stratovolcano can also be called a composite volcano- or a volcano made of layers of hardened lava flow and pyroclastic materials. It is situated where the Pacific Plate, which is an oceanic plate, is colliding and subducting under other similar plates.
Thursday, March 26, 2009
The Shishaldin Volcano is located in Alaska, United States. It is close to the cities Akutan and Cold Bay, which are relatively unknown towns when compared to Anchorage, Alaska, which Shishaldin it is 1100 kilometers away from. Shishaldin is found along a line that is commonly referred to as "The Ring of Fire". The Ring of Fire is an extensive zone of volcanic activity where the Pacific Plate is colliding and subducting beneath other plates, meaning the Shishaldin Volcano formed on a subduction boundary. It is the highest peak, at 2857 meters tall, in the Aleutian Islands
The Shishaldin Volcano is extremely active. It has undergone many eruptions over the past two decades, including major eruptions in 1993, 1995, 1997, and 2004. It suffered two particularly violent eruptions in 1830 and 1932, but probably the most famous of eruptions occured in 1999.Between March 13 and May 27, the Shishaldin Volcano erupted after several months of earthquakes and other signs of volcanic unrest like tremors of low frequency signifying ash explosions. When spewing ash upwards of between 15 and 20 kilometers, the Shishaldin euption reached it peak on April 19. Basaltic lava flowed down the northern flank of the mountain. It was the largest eruption seen at Shishaldin in the last 175 years. Thankfully, Shishaldin is not near enough to surrounding towns to cause severe devastation, but it did damage seismic instrumentation.
Shishaldin is part of the Aleutian Islands, which are extremely volcanicly active because they are part of the Ring of Fire, where the Pacific Plate is continually subducting under other plates. The Wrangell Mountain chain covers over 2000 square miles and is volcanicly active. it includes one of the largest active volcanoes in the world. Wrangell is a shield volcano and has a caldera at its summit although it only has minor steam plumes and phreatic ash. Also near Shishaldin is the Spurr Volcano, which is a stratovolcano as Shishaldin is as well. it also has a large explosion caldera. Its mean peak has not experience eruption in what scientists have predicted, over 10000 years. Its smaller peak, Crater Peak, has erupted in 1953 and 1992, showering ash on Anchorage, Alaska. Crater Peak is still monitored closely.
Wednesday, March 25, 2009
The Shishaldin Volcano is not very explosive, possessing basaltic lava, which is extremely dense. When erupting, the volcano can spew ash 20 kilometers into the air, making any air traffic potentially lethal. Ash clouds can destroy plane engines and other electronics, and ash clouds can drift and affect other, further, nations. Eruptions can also melt polar icecaps, causing massive flooding, as well as lahars, which are mudslides made of volcanic fragments. Pyroclastic flows are also common. They are strong and incredibly hot surges of semi solid material and they destroy everything in their path. Lava flows are also common.
The Shishaldin Volcano affects the environment in both positive and negative ways. Harmful gases are emitted into the air during eruptions and stay in the air for long periods of time. Shishaldin can cause large pyrocalstic flows but, luckily, it is far enough away from any major towns to prevent any catastrophic damage. Few people visit the mountain and there are no towns near enough to be harmed.