To get a good sampling of lava, geologists must carefully extract the fiery substance as it boils and flows. Reaching temperatures up to 2500 degrees Fahrenheit, lava is a dangerous substance and can burn through almost any material. Therefore, geologists collect their lava samples in coffee cans that will not melt from the high lava temperatures.

Sampling from a Skylight

One place a geologist might get a lava sample is from a crack in the earth through which a flowing river, or tube, of lava can be seen. This crack, called a "skylight", is a place where the roof of the lava tube has collapsed. Before taking a lava sample, the geologist will attempt to guess the depth of the lava flow. Usually, it's not possible to simply stand over a skylight and figure out how deep it is—it's difficult to get close enough to see much of anything, and in general this would be too dangerous. Instead, the geologist tosses a length of steel cable attached to a sampling can into the lava, and then drags it back out.

What Can Go Wrong

Sometimes, the sampling can is tossed too far into the lava. The lava burns right through the chain, and the can is lost. Other times, the sampling can gets stuck on the side of the skylight as it is being pulled out. About one out of every five samples a geologist attempts to get from a lava flow is lost due to the can being caught or separated from the chain.

Why Water Lava?

If lava is allowed to cool slowly over a few hours, the chemical make-up of the lava changes drastically from its hot form. In order to preserve the chemical fingerprint of hot lava, geologists immediately pour cold water onto their lava sample, to cool it down quickly. In this way, the chemical "picture" of the volcano's lava is preserved. The scientists can then conduct a chemical analysis of the sample, to learn more about the volcano and how (and when) it was formed.