Volcano Watch: Mapping New Lava

Geologists everywhere like to study rocks in the field, but few of them get to map rocks that are still molten and on the move. In Hawaii, scientists with the U.S. Geological Survey map the new lava flows erupted from Kilauea Volcano to determine their extent and volume.

Mapping also helps to keep track of how fast flows are advancing toward areas where people live. In the past three years, the way scientists map lava has undergone a revolution. Instead of trying to figure out a flow's location and then mark it on paper maps or aerial photographs, scientists now map with portable GPS (Global Positioning System) receivers.

These devices receive the radio waves from global positioning system satellites to determine the position of the receiver on the Earth's surface. Portable receivers record positions to within 15 feet, which is well suited for lava-flow maps.

To map flows, scientists walk around them as near their edges as possible, noting their characteristics and position. With GPS receivers, the position is recorded by pushing a button, and the data are recorded in the computerized memory of the device. Back in the office, scientists download the coordinates and connect the dots, so to speak. The result is an outline of the lava flow.

It's easy to distinguish the margin of a new flow where it laps against substantially older flows. New flow is a shiny, silvery gray color, because none of its glass, which forms most of the rock, has altered chemically or physically. If the flow is less than a week old, scientists may feel substantial heat as we approach it or step onto it. Shimmering heat waves in the air above a recent lava flow may give it away, too.

If the mapping doesn't begin until the flow is cool, it can be more difficult to recognize new flow from old flows. Scientists will look for other clues, including burned trees or brush, ash from the burned vegetation and subtle differences in color. Scientists say that the law flows begin to revegetate quickly - meaning plants return to the area. Even near flows only a few months old, tiny ferns can be seen sprouting where moisture collects.