Tuesday, April 6, 2010
Avalanche, Volcano and Earthquake are the big ones.
An avalanche can be make up of rocks, mud and/or snow but all can be quite deadly.
You'll be driving through the mountains and see signs to beware of falling rocks, some falling rocks closed I-70 near Vail because boulders the size of school buses smashed through the pavement.
Rock avalanches often happen in the Spring and Fall when the temperature swings below freezing at night and above during the day. Water from rain or snow runoff has gotten between the rocks and when it freezes forces the rocks apart.
Mudslides often occur in the rainy season after a wildfire. The ground becomes soft from the rain but all the vegetation was burnt off in the fire. There is nothing to hold it all together.
Snow is more complex it depends on how the types of previous snows and how they have layered up. If you are caught in one you might die of asphyxiation.
They can also be caused by earthquake. There is more then enough force in an avalanche to destroy cars and buildings and kill people. Most people are smart enough not to live at the bottom of a cliff or build on top of one that can give way.
Earthquakes are top of mind right now after the ones in Haiti and Chile. They tend to cause earth movements which can cut utilities and damage transportation infrastructure making getting food and supplies harder. Obviously it will also damage and destroy buildings.
Other effects include avalanche, soil liquefaction (the ground acts like water and buildings sink), sinkholes, and if underwater, tsunamis (which cause flooding).
Finally, volcanoes or an exploding mountain.
Volcanoes tend to cause one or more of the following: Pyroclastic flows (fast moving clouds of gas and ash that fry everything in their path), Lava (molten rock) flows, Lahar (mudflow), Ashfall, and Ejecta (flying rocks, boulders and debris). Some volcanoes like the ones in Hawaii are quite calm just producing lots of lava. Others like Mount St. Helens explode with the force of multiple nuclear weapons.
Volcanos have destroyed plenty of cities throughout history and even brought down civilizations. A super-volcano may have even caused a mass extinction event millions of years ago. If a foot of snow is hard to get around in what is a foot of ash going to do, ash doesn't melt.