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Geology and Remote Sensing of Mt. Pinatubo & Taal Volcanoes, the Philippines Peter Mouginis-Mark University of Hawaii pmm@pgd.hawaii.edu Work funded by NASA’s Solid Earth and Natural Hazards Program
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LOCATION OF VOLCANOES IN THE PHILIPPINES
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Landsat 7 coverage (obtained over 3 different days)
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Mt. PINATUBO ERUPTIONS June 1991
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Prior to eruption
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Fumaroles on flanks, April 1991
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June 12th, 1991 eruption
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Giant pyroclastic flows, June 15th 1991 form off of collapsing eruption column
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The view from space via the Japanese GMS-5 geostationary satellite
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Early effects on the ground
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Sediment-laden rivers destroy roads & bridges
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Major landscape changes: Pyroclastic flows in-filled pre-existing river valleys (the peaks in two views below are the same feature)
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AIR PHOTOS
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Summit caldera of Mt. Pinatubo, Nov. 1999. The low-point in the rim is a future hazard as the lake will eventually over-top here.
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Typical view of eastern flank, Nov. 1999
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Erosion of ignimbrite fan on NW. flank, November 1999
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Erosion of river valley on the northern flank, Nov. 1999
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Sediment fills valley floor downslope on lower E. flank November 1999
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Detail of lahar-filled valley E. flank, Nov. 1999
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GROUND PHOTOS
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Exploring eroded valley, SW flank Nov. 1999
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Crossing the sediment-laden streams is a real challenge! So much sediment is in these streams that they easily knock you over.
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Valley erosion can be extreme in places: Up to 20 m down-cutting during one typhoon! This mosaic shows the remains of the 1991 deposit (white unit) that has been cut by younger flash floods
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Erosion within the 1991 deposit
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Erosion of 1991 deposit
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Amazing landscapes!
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Vegetation is starting to grow back on western fan. Summit of Mt. Pinatubo in background
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“LAHARS” (MUDFLOWS) AND THE RESULTANT DAMAGE
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Major changes in valley floor elevation after single lahar has formed after typhoon.
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The impact on villages within the path of a lahar can be extreme
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While old houses are buried, new homes are built on stilts to try to avoid the next lahar
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An old church has been partially-buried so that you now enter on the 2nd floor. Ronnie Torres shows the church prior to the lahars.
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Giant dikes made from old lahar and covered with concrete now try to protect areas from new lahars
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The contrast between areas protected by the dikes and unprotected is striking -- and it’s all an issue of insurance for redevelopment!
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Some homes, once buried by lahar, and now being exposed by recent erosion
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REMOTE SENSING DATA
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Landsat 7 Path 116 Row 50
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RADARSAT radar backscatter image of Mt. Pinatubo, February 1998
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SPOT image of Mt. Pinatubo December 1991
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RADARSAT radar backscatter image of western fan of Mt. Pinatubo
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Clark Air Base: RADARSAT standard beam data set (25 m/pixel)
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SPOT data of Mt. Pinatubo summit area soon after the eruption
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Comparison of NW Summit from SPOT data obtained between 1991 and 1998 Red shows vegetation, the ash deposits are light blue Summit is at lower right
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Changes in Mt. Pinatubo lahar deposits. Lower Pasig-Potrero River 1991 - 1996
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ERS-1 radar backscatter image of Pasig-Potrero River showing low-backscatter lahar deposits
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Shaded relief image of lahar fans SE of Mt. Pinatubo summit from NASA TOPSAR topographic data
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Nighttime Landsat 7 thermal data of Mt. Pinatubo shows warm streams
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TAAL VOLCANO (just south of Manila)
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RADARSAT scansar beam 1 (50 m/pixel) image of Taal Volcano and surrounding area
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Space Shuttle radar (SIR-C/X-SAR) multi-wavelength (3, 5.6 and 24 cm) image of northern part of Taal Volcano
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View of Lake Taal and Volcano Island from north rim, Nov. 1999
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NW corner of Lake Taal
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Over 4,000 people live without permission on the shores of Volcano Island
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In the event of an eruption of Taal, all the population would have to leave Volcano Island via small boats
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View of the volcanic lake in middle of Volcano Island (middle of Lake Taal)
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In Fall 1999, this vent on Volcano Island was actively geysering. It was quiet in November 1999.
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Close-up view of recently active vent on Volcano Island, in the middle of Taal Volcano
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Even around the rim of Lake Taal, people and their fish farms are at risk from tsunamis generated by eruptions.
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