Geology and Remote Sensing ofMt. Pinatubo & Taal Volcanoes,

the Philippines

Peter Mouginis-MarkUniversity of Hawaii pmm@pgd.hawaii.edu

Work funded by NASA’s

Solid Earth and Natural Hazards Program

LOCATION OF VOLCANOESIN THE PHILIPPINES

Landsat 7 coverage(obtained over 3 different days)

Mt. PINATUBO ERUPTIONSJune 1991

Prior to eruption

Fumaroles on flanks, April 1991

June 12th, 1991 eruption

Giant pyroclastic flows, June 15th 1991form off of collapsing eruption column

The view from space via theJapanese 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. 1999.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 onNW. flank, November 1999

Erosion of river valley on thenorthern flank, Nov. 1999

Sediment fills valley floor downslope on lower E. flank November 1999

Detail of lahar-filled valleyE. flank, Nov. 1999

GROUND PHOTOS

Exploring eroded valley, SW flankNov. 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

Amazinglandscapes!

Vegetation is starting to grow back on westernfan. Summit of Mt. Pinatubo in background

“LAHARS” (MUDFLOWS) AND

THE RESULTANT DAMAGE

Major changes in valley floor elevation aftersingle lahar has formed after typhoon.

The impact on villages within the path of a lahar can be extreme

While old houses are buried, new homesare built on stilts to try to avoid the next lahar

An old church has been partially-buried sothat you now enter on the 2nd floor. RonnieTorres shows the church prior to the lahars.

Giant dikes made from old lahar and covered withconcrete now try to protect areas from new lahars

The contrast between areas protected by thedikes and unprotected is striking -- and it’s

all an issue of insurance for redevelopment!

Some homes, once buried by lahar, andnow being exposed by recent erosion

REMOTE SENSINGDATA

Landsat 7Path 116Row 50

RADARSAT radar backscatter imageof 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 Summitfrom SPOT dataobtained between1991 and 1998

Red showsvegetation,the ash depositsare light blue

Summit is atlower right

Changes in Mt. Pinatubo lahar deposits. Lower Pasig-Potrero River 1991 - 1996

ERS-1 radar backscatter image ofPasig-Potrero River showing

low-backscatter lahar deposits

Shaded relief image of lahar fans SE ofMt. Pinatubo summit from NASA TOPSAR topographic data

Nighttime Landsat 7 thermal dataof Mt. Pinatubo shows warm streams

TAAL VOLCANO(just south of Manila)

RADARSATscansar beam 1(50 m/pixel)image of TaalVolcano andsurroundingarea

Space Shuttle radar(SIR-C/X-SAR)multi-wavelength(3, 5.6 and 24 cm)image of northernpart 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 viewof recently activevent on VolcanoIsland, in themiddle of Taal Volcano

Even around the rim of Lake Taal, people and their fish farms are at risk from

tsunamis generated by eruptions.