Observations of vertical heat flux in basalt, Hawaii Volcanoes National Park, Hawaii, USA.

Authors: Steven J. Gordon*, US Air Force Academy, Frederick B. Chambers, University of Colorado - Denver
Topics: Physical Geography, Climatology and Meteorology, Geomorphology
Keywords: basalt, microclimatology, Hawaii
Session Type: Poster
Day: 4/4/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Our study addresses the transfer of energy to and from the surface of emplaced pahoehoe basalt to the subsurface. This transfer depends greatly upon the thermal conductivity property of the basalt. Thermal conductivity is dependent upon many factors. A number of studies of thermal conductivity of basalt measure the property under laboratory conditions, rather than in the field.
Measurements of lava temperatures approximately 2 and 4cm below the surface have been carried out over the past two years in order to assess heat flux through the material when exposed to a variety of meteorological conditions. Standard weather measurements of wind direction/speed (at 2m above surface), temperature/relative humidity (both 1m above surface), precipitation, barometric pressure, and short wave in/out (at 1m above surface) were also observed at an adjacent logging weather station. Results appear to indicate that the dark (albedo averages of about 5%) vesicular lava is quite responsive to incoming short-wave radiation with temperatures spiking at both levels shortly after sunrise and peaking at solar noon on each day. Differences in temperature (dT) between the two recorded depths (~2cm) also rise and are commonly seen to approach nearly 13 degrees C, also shortly after solar noon. These differences decrease and reverse as energy is lost to the surface nocturnally.

The heat flux in the upper few centimeters of the pahoehoe impacts weathering of the paheohoe at the surface and in the upper crust, by determining in part the energy available for chemical processes and also physical stresses.

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