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.
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