Re: What tools do volcanologists use to predict eruptions?

Scientists are getting better and better at predicting when a volcano will erupt; however they still have a long way to go. This is because every type of volcano, and furthermore, every individual volcano, has its own character and suite of phenomena before an eruption. The basic procedure scientists use involves characterizing the behavior of a volcano prior to an eruption and then looking for that same behavior again to predict when it will erupt again. If a volcano has never erupted before, then scientists must compare this volcano against other volcanoes of similar type. Of course, this second way of forecasting is not quite as precise.

I will describe some of the tools scientists use to characterize a volcano prior to an eruption, but you might find the content of these web pages interesting:

http:// volcanoes.usgs.gov/Products/Warn/warn.html

http://library.thinkquest.org/J003007/Disasters2/ volcano/predicting/predict.htm

http://www2.ios.com/~dobran/ gvs.html

When a volcano is about to erupt, several changes typically occur. These include changes in, temperature, gas emissions, earthquake frequency, the level of the ground around the volcano, and gravity. I will treat each phenomenon in the order I have listed them here.

Scientists measure the temperature of the ground with pretty much standard thermometers. But they can also use satellite data, which measures the temperature of the ground over large regions, to characterize changes in the temperature of the earth. Every measurement of temperature is difficult because changes in temperature due to volcanic activity need to be separated from changes due to weather.

In the regions around volcanoes, scientists take samples of gas that is trapped in the soil near the surface. Prior to an eruption, carbon dioxide and sulfur dioxide are typically found in increasing concentrations because the pressure of these gasses increases around the magma that is trying to force its way out. Magma pressure is a fundamental quality, which, if it could be measured directly, would tell us when a volcano would erupt. Gas emissions are not only just an indicator, but can be dangerous to humans and wildlife. In the vicinity of Mammoth mountain in California, the concentration of carbon dioxide has increased so much that it is killing the trees all over the mountain!

How often scientists detect small earthquakes is one of the most important tools towards volcano prediction. As magma starts to move around under the earth, small earthquakes are set off, which would not occur if the volcano were "non-active". Earthquakes are detected using a seismometer. The web page at thinkquest.org describes how a seismometer works.

Believe it or not, but the magma pushing against the underside of the earth’s crust, can cause changes in the level and elevation of the surface! Scientists measure this change with standard surveying equipment like you might see road crews using near your home. They also can use high precision Global Positioning Systems (GPS), which use satellites to find detailed earth positions, including elevation.

Finally, magma is typically less dense (it weighs less for the same volume of material) than the hot rock it is moving around under the surface. This means that the gravity of the earth will be different directly over the magma! This is a very small change (you won’t feel lighter if you walked over the magma) but with precise Gravimeters (devices that measure gravity) scientist can measure this change. Knowing where the magma is and how much is there can indicate when an eruption will occur as well as how big it will be.

I hope this helps answer your question! Don’t forget to read cool magazines like "Scientific American" (and check their web site: http://www.sciam.com ) for information about volcanoes and volcano prediction.