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... on of material into the air. Nonexplosive eruptions produce lava flows and eject very little pyroclastic material into the air. Explosive eruptions can eject liquid and semisolid lava as well as solid fragments of volcanic or nonvolcanic rock that have been carried along by the rising magma before eruption. Very violent explosive eruptions are called Plin ian eruptions, after Roman naturalist Pliny the Elder.
These eruptions can last for several hours to days and eject a large amount of pyroclastic material. Some volcanoes can produce much more energetic eruptions that eject materials farther from the vents because of their andesites and diacritic composition. Andesitic and diacritic lava is generally thicker than basaltic lava. Stiff lava generally produces more-explosive eruptions. If the eruption is nonexplosive, as is typical for Hawaiian volcanoes, lava flows are produced.
The lava comes out of rifts in the sides of the volcano, or vents in a rift. Tephra is rarely ejected during a nonexplosive eruption. Nonexplosive eruptions are characterized by basaltic lava and by the type of volcanoes they form, called shield Aerial view of Mount St. Helen in Washington Volcanic eruptions can hurl hot rocks for at least 20 miles. Floods, airborne ash, or noxious fumes can spread 100 miles or more.
If you live near a known volcano, active or dormant, be ready to evacuate at a Learn about your community warning systems. Be prepared for these disasters that can be spawned by volcanoes. Landslides and mudflows You want to get to high ground away from the eruption. Plan a route out and have a backup route in mind. Develop an emergency communication plan.
In case family members are separated from one another during a volcanic eruption (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together. Ask an out-of-state relative or friend to serve as the "family contact. " After a disaster, it's often easier to call long distance. Make sure everyone knows the name, address, and phone number of the contact Have disaster supplies on hand. Flashlight and extra batteries Portable, battery-operated radio and extra batteries First aid kit and manual Emergency food and water Nonelectric can opener Essential medicines Cash and credit cards Get a pair of goggles and a throw-away breathing mask for each member of the household. Contact your local emergency management office or American Red Cross chapter for more information on volcanoes. Although it may seem safe to stay at home and wait out an eruption, doing so could be very dangerous.
The rock debris from a volcano can break windows and set buildings on fire. Stay safe. Follow authorities' instructions and leave the area before the disaster begins. Follow the evacuation order issued by authorities. Avoid areas downwind of the volcano. Close all windows, doors, and dampers.
Put all machinery inside a garage or barn. Bring animals and livestock into closed shelters. Seek shelter indoors. If caught in a rockfall, roll into a ball to protect head. Avoid low-lying area where poisonous gases can collect and flash floods can be most dangerous. If caught near a stream, beware of mudflows.
Wear long sleeved shirts and pants. Use goggles to protect eyes. Use a dust-mask or hold a damp cloth over face to help Keep car or truck engines off. A lateral blast of a volcano can travel many miles from the mountain. Trying to watch an erupting volcano is a deadly idea. Mudflows are powerful "rivers" of mud that can move faster than people can walk or run.
Mudflows occur when rain falls through ash-carrying clouds or when rivers are date during an eruption. They are most dangerous close to stream channels. When you approach a bridge, first look upstream. If a mudflow is approaching or moving beneath the bridge, do not cross the bridge. The power of the mudflow can destroy Listen to a battery-powered radio or television for the latest emergency Stay away from volcanic ash fall.
Cover your mouth and nose. A number of victims of the Mount St. Helens volcano died from inhaling ash. Wear goggles to protect your eyes. Keep skin covered to avoid irritation or burns. If you have a respiratory ailment, avoid contact with any amount of ash.
Stay indoors until local health officials advise it is safe to go outside. Avoid driving in heavy ash fall. Driving will stir up more ash that can clog engines and stall vehicles. Ash fall is very heavy and can cause buildings to collapse. Remember to help your neighbors who may require special assistance -- infants, elderly people, and people with disabilities. Is Chemistry Involved in Studying Volcanoes?
Chemistry is involved for studying volcanoes in a number of ways. For one thing, volcanologist's (scientist who study volcanoes) are often interested in the processes that go on down deep within a volcano such as within a magma chamber. By studying in detail the chemical characteristics of some of the minerals in a volcanic rock, they can start to get a handle on these processes. They can also start to understand what goes on when the first magma is produced. For example, when the upper mantle starts to partially melt to produce magma, not all the minerals in the mantle melt at the same rate. Some start melting first so their chemical constituents will be concentrated in the first blobs of melt.
As melting continues other minerals start to melt as well, and the chemistry of the magma changes. From studies like this geologists have determined that the early stages of a Hawaiian volcano's life is generated by magmas derived from only small degrees of partial melting (such as only 5 % of the source melting and the rest staying behind). On the other hand, when the volcano really gets going (such as at Kilauea and Mauna Loa), the percentage of source rock that melts to produce the magma is perhaps as high as 20 %. There are many other ways in which chemistry is used in volcanology, including the studies of volcanic gases, crater lakes, and trying to determine the temperatures that lava had at the time they were erupted even long after the eruption has ended. Bibliography: Bibliography 1999 Microsoft Encarta; Volcanoes 1980 USGS; web 2000 Volcano World; web 1980 - 2000 USGS; web 1993 - 2000 Microsoft Corporation; various volcano media 2000 FEMA; web
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