As Okmok caldera in Alaska continues to erupt I thought it would be appropriate to outline some of the potential hazards faced by those who occupy that area and any area around an active volcano. Today’s portion is about volcanic ash.
While seemingly annoying and non-threatning volcanic ash is one of the biggest hazards from an erupting volcano. The photo above shows a piece of volcanic ash from the 1980 eruption of Mount St. Helens in Washington State.
One of the most common misconceptions about volcanic ash is that it is the same material found in your fireplace or charcoal grill. Unfortunately that could not be further from the truth. While normal ashes found around the house or normally organic based remains of whatever was burned volcanic ash is actually tiny pieces of rock. This particular sample is only 30 microns across and can only be seen well under 200x magnification.
When this ash falls over an area it is devestating in many ways. For instance if a jet airliner were to fly through an ash cloud it would be like flying into a giant sandblaster. The ash ingested into the engines melts over fuel nozzles and other critical engine parts causing the engines to shut down. However aircraft that have entered an ash cloud can usually re-start they’re engines when they reach clear air. By now the damage has been done. The engines are badly damaged and now the pilot must make an emergency landing. However the cockpit windows would be scratched so badly that you could not see out of them forcing the pilots to land blind. To help pilots avoid these clouds Volcanic Ash Advisory Centers (or VAAC) ws established. To learn more about their mission please visit: http://www.ssd.noaa.gov/VAAC/washington.html
Not all of the trouble is in the air. On the ground underneath the cloud day quickly turns to night. And after the cloud dissapates the area is left with a surreal “moon” type of landscape.
in this photo a helicopter attempts to land in the area around Mt. St. Helens after it’s eruption in 1980. Note the barren grey landscape.
Another danger from ash is accumulation. Being composed of rock ash is extremely dense and when accumulated in large ammounts will quickly collapse the roofs of buildings. There are many occasions in which rain follows a volcanic event and the moisture added to ash only increase its weight.
Rain also triggers another volcanic hazard called a Lahar which is a volcanic mudflow. We will discuss this more at length in the next segment.
Finally, the greatest hazard put forth by the ash is the fact it can be breathed in. Ash is much like powdered concrete and upon inhalation the ash mixes with moisture in the lungs. The victim essentially drowns in “liqiud concrete”.
This posting does not cover all of the hazards associated by ashfall and is meant for information purposes only. To learn more about ashfall please visit: http://volcanoes.usgs.gov/ash/
For additional information on eruptions taking place around the globe see the blog by Volcanologist Dr. Erik Klemetti at http://eruptions.wordpress.com
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I must plead ignorance to all I have read here and feel that I have been done a service. What a fascinating blog, one hopes you are more than successful in your educational pursuit, you are obviously going for A+ student. Best of luck, will visit more often. Glenn