Answer: The type of equipment and techniques we use to study volcanoes depends on the particular volcano topic we are investigating and on the experiment we are conducting. When specialized instruments are not available for a special study or for monitoring a specific type of activity, we design and build our own; for example the acoustic flow monitor (AFM) for detecting lahars and an experimental flume for studying flowing mixtures of water and rock debris under controlled conditions.
For studying and monitoring restless and erupting volcanoes, several onsite and remote methods are used to gather data that also help us answer four critical questions during a volcano emergency.
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For reconstructing a volcano's eruptive history so that we can identify the type of activity most likely to occur in the future as well as the areas around a volcano that are likely to be effected by future eruptions, we use many geologic mapping and dating strategies. These include:
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Identifying rock outcrops, formations, and features on the ground and identifying their exact location on detailed aerial photographs and topographic maps or in computerized geographic information systems (GIS).
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Collecting dozens to hundreds of volcanic rock and ash samples from sites located on or near the volcano and also tens of kilometers downwind or downstream, and then using laboratory techniques for determining their chemistry and mineral compositions.
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Determining the ages of as many rock deposits formed by past activity of the volcano by using several common methods:
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Carbon-14 dating when a volcanic deposit either incorporated or came to rest on top of vegetation or organic-rich soil and sufficient carbon-bearing material can be found. It's based on the fact that living trees and other organic matter contain small amounts of carbon's radioactive isotope (atomic weight of 14). When a tree is killed by a volcanic deposit, its radioactive carbon begins to decrease by radioactive decay at a known rate. By measuring the 14C/12C ratio in the wood sample, its age can be calculated. This technique can adequately date deposits that are as old as about 50,000 years, and each date may have an error range of between a few tens to several hundred years. The most common technique for dating recent volcanic deposits, only a few scientific laboratories in the United States can perform the carbon analysis.
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Tree-ring dating when a volcanic deposit caused an unusual growth pattern of annual rings among trees growing at the time the deposits were emplaced. This technique can sometimes date deposits to an actual calendar year or to within a few years when used to on deposits of the past few hundred years.
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Paleomagnetism in some volcanic areas where scientists have determined the yearly changes in the position of the Earth's magnetic pole over the past several hundreds or thousands of years and when the Earth's magnetic direction is preserved in volcanic rocks (usually lava flows and individual large rocks in pyroclastic flows); this technique usually yields ages with a range of between a few tens and several hundred years.
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Representing the types and ages of volcanic rock deposits and/or identifying volcanic hazard areas around the volcano on a paper map or computerized geographic information system.
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