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