Scientists at NASA's Jet Propulsion Laboratory, Pasadena, Calif., say images of Kilauea volcano on the island of Hawaii show there are distinct differences in heat emission from different lava flows even though the lavas are all very similar in composition (olivine-bearing basalts).

Drs. Alan R. Gillespie, Anne B. Kahle and Michael J. Abrams presented their findings at session of the annual fall meeting of the American Geophysical Union, now meeting in San Francisco.

The remote sensor used in the study was the Airborne Thermal Infrared Multispectral Scanner (TIMS).

Gillespie, currently on assignment at University of Washington Geology Department, Seattle, and his colleagues attributed the differences to two causes: differences in surface roughness of the lava, and mechanical and chemical changes in surface composition during weathering.

A rough surface will emit higher fraction of blackbody, or emitted, radiation than smooth surface because of the multiple reflections of the radiation emitted from surface irregularities.

Weathering affects the heat emissions in at least two ways. One is the destruction of thin glassy rinds that coat new "pahohoe" or smooth lava surfaces, and the second is chemical alteration of exposed lava. At Kilauea these effects occur in systematic way on time scale of tens to hundreds of years.

The scientists said that remotely sensed thermal emittance measurements appear to form convenient, quantitative basis for the relative dating of young basalts, and are therefore important tools in understanding the history of many volcano eruptions.

Kilauea recently began erupting. It sent seven mile-long river of lava to the sea, destroyed several homes, and added at least 13 acres to the island.

Research conducted by the Gillespie led team was funded by the Land Processes Banch, Office of Space Science and Applications, NASA, Headquarters, Washington, D.C.

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