Draft volcano primer: Mt. Pinatubo and Taal volcanoes, the Philippines. 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. - PowerPoint PPT Presentation
Transcript of Draft volcano primer: Mt. Pinatubo and Taal volcanoes, the Philippines
Draft volcano primer:Mt. Pinatubo and Taal volcanoes,
the Philippines
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(recent views)
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 of 1991 deposit
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
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
TAAL VOLCANO(just south of Manila)
RADARSATscansar beam 1(50 m/pixel)image of TaalVolcano andsurroundingarea
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.
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.