EOS Volcanology Logo University of Hawaii: EOS Volcanology, Thermal and Topographic Studies

Sample Images
Surface Change (62K image)
One of the new techniques being developed by the EOS Volcanology Team is the detection and quantification of the changes in area of new lava flows using repeat-pass radar interferometry. This technique has been demonstrated using data from the second SIR-C flight in October, 1994. In the top panel, we see the area of interest just south of Pu'u O'o cone in Hawaii. The active areas are labelled 1, 2, and 3. In the middle panels, are field photos that we took during the period of radar observations, with the red arrows correlating specific areas that were active with the radar images in the third row. These radar images show the degree of correlation between successive observations taken one day apart. Pink areas have zero correlation, meaning that a new lava flow has formed sometime over the last 24 hours. Yellow is higher correlation, associated with old flows. These data have been used by Zebker et al. (1996) to estimate a volume of eruption of 2 cubic meters per second over the four days of observations.

Mauna Kea Topography (133K image)
Data validation will be a very important aspect of the radar determination of topography. Repeat-pass interferometry with the SIR-C L-band radar was used over Hawaii to produce a digital elevation model. Here we see (at left) a shaded relief map of the volcano Mauna Kea. While these data look quite good, on comparison with the USGS DEM (which has 30 meter postings) there are several areas where the two data sets differ by more than 100 meters. These differences are believed to be due to atmospheric effects in the radar data. The EOS IDS team is working to develop techiques to identify and reduce this type of error, because in many parts of the world we will have to rely on the radar interferometry to produce the DEM.

SIR-C Hawaii (351K image)
In April 1994, the Space Shuttle Endeavor carried an imaging radar system called SIR-C / X-SAR. Several of the EOS Volcanology IDS Team, including Pete Mouginis-Mark, Chuck Wood and Howard Zebker participated in numerous volcanology experiments using with this radar. Here we see the combination of C-band (5.6 cm) and L-band (24 cm) wavelength radar data for Kilauea Volcano, Hawaii. Particularly interesting is the range of colors (produced by the different radar backscatter properties at different wavelengths and polarizations) of the lava flows from Mauna Ulu and Pu'u O'o. These flows are both a'a and pahoehoe, which have a rough and smooth texture, respectively. The dark area south of Kilauea caldera is due to the ash deposits from the big explosive eruption in 1790. This ash absorbs most of the radar energy.

SIR-C Pinatubo (423K image)
In April 1994, the Space Shuttle Endeavor carried an imaging radar system called SIR-C / X-SAR. Several members of the EOS Volcanology IDS Team, including Pete Mouginis-Mark, Chuck Wood and Howard Zebker, participated in numerous volcanology experiments using this radar. SIR-C/X-SAR imaged Pinatubo volcano in the Philippines at different wavelengths and polarizations. Here the pyroclastic flows are shown in red, to help distinguish them from the vegetated flanks of the volcano. This contrast is due to the absorption of the short wavelength (C-band, 5.6 cm) radar data. The very dark areas are river valleys buried by lahar deposits. One of the most interesting aspects of the SIR-C/X-SAR mission will be to compare this view of Pinatubo with comparable data taken during the second flight of the radar in August 1994. It is possible that new lahars will change the morphology of the downslope areas. This may enable us to evaluate the volcanic hazards in the area.

Field spectrometer (284K image)
One of the main topics of research for the EOS Volcanology Team is the investigation of the thermal properties of lava flows. Here we see two of our Team at the Phase 50 eruption of Pu'u O'o volcano, Hawaii, in February, 1992. The white box on the tripod is a spectroradiometer, which collects high precision radiance data over the wavelength range 0.4 to 3.0 micrometers. These data enable us to determine the temperature and percent surface area of the lava flow, which in turn lets us predict the type of thermal anomalies that will be observed by ASTER and MODIS on the EOS platforms. We are also using this information to test thermal alarms, so that we can automatically detect new eruptions anywhere around the world using MODIS data.

Landsat images of Hawaii (262K image)
Landsat data have been used to study the distribution of thermal anomalies on active lava flows in Hawaii. Here we see data from July, 1991. In addition to surface activity, the thermal data (Band 6) can be used to detect lava tubes. These data hint at the type of analysis that we will be able to conduct with ASTER data from EOS.

Thermal Energy Map of a Lava Flow (39K image)
In order to investigate the magnitude of an eruption, the EOS Volcanology team has been developing algorithms for the measurement of energy emitted from the surface of an active lava flow. Here we see how the Landsat data for bands 4, 5, 6, and 7 (5 and 6 shown in the previous image) can be processed to show the radiant flux density (in Watts per square meter) for the entire lava flow. North is towards top of the image. Energy values range from less than 500 Watts per square meter (in black) to more than 5,500 Watts/sq. meter (in brown). Maps such as these will be made from ASTER and MODIS data, and will enable us to rapidly evaluate the degree of vigor of an eruption, and hence the potential hazards posed by this activity.

The Big Island of Hawaii: Landsat (287K)
Building databases against which we can compare future eruptions is an important part of the EOS Volcanology project. Here we see a mosaic of Landsat Thematic Mapper images that have been merged with a digital elevation model of Hawaii. Such information is also being used to test models of the emplacement of lava flows, which relates to the study of volcanic hazards due to eruptions.

TOPSAR Relief: Kilauea (383K image)
The NASA TOPSAR instrument is being heavily used by the EOS Volcanology Team to collect high resolution digital elevation models (DEMs) of volcanoes. TOPSAR measures topography with 10 meter spatial resolution and about 2 meter vertical accuracy. Here we see a TOPSAR DEM of the East Rift Zone of Kilauea volcano, Hawaii. This DEM has been processed in a computer so that it is seen as a shaded relief map of the rift zone. Areas of recent activity, such as the Pu'u O'o cone and the Kupaianaha lava shield are seen at the top right of this view.

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