philippines tectonics

7/28/2019 Philippines Tectonics

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By: Java, John Aldrin, Go Patrick, Managa Nylle

3CS


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Indeed the plate is squeezed inbetween the Eurasian plate andthe Pacific Plate, but the situationis more complex than that.

The Philippine Islands aresurrounded by complex plateboundaries, and the PhilippinesPlate rather consists of severalmicro-plates - squeezed in betweentwo convergent plate margins.


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The lines with black triangles are active subductionzones with teeth on the over-riding plate.

Lines with white triangles are passive subductionzones with teeth on the over-riding plate.

The major Philippine fault zone is shown as a blackline with arrows showing the movement direction.The volcanoes Pinatubo and Mayon are shown asred dots.

Thevolcanoes of the Philippines are probably the

most deadly in world. They are concentrated in a northern volcanic arc

above and east of the north-western subduction zone(Manila Trench) and in a southern volcanic arcabove and west of the south-eastern subduction zone(Philippine trench).

The Sulu trench also produce a (discontinuous) lineof active volcanoes.

The Mayon volcano may be associated with thetransform fault that connects the eastern and thewestern subduction zones.

This transform fault is offset by the younger north-south directed Philippine Fault


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The Philippine is estimated to have formed during

the Pleistocene Period 2 million B.C. It has distinctgeographical features and has an array of land andwater forms. These can all be explained by the PlateTectonic Theory.

ICE AGE


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The Philippine is the product ofthe continental drift of the Philippine

Sea Plate.

The collision of the Eurasianplate and the Philippine Sea plate

with the Pacific plate and Indian-Australian plate created the currentlow and high lands, islands and seas inthe Philippines.

Evidences of these were the SierraMadre range and Zambales range inthe eastern upward movement ofthe Philippine Sea while it was beingsqueezed between the movement of

the Eurasian plate and the Pacific plate.


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The Philippines was considered

as Proto-Philippine with theislands of Bicol, Leyte,and Eastern Mindanao that

were formed during theCretaceous Period100-65 million

B.C.

It was concentrated inthe Equatorial Zone in betweenthe Philippine Sea Plate and

the Eurasian plate which servedas the first islands that shapedthe country.


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Back then Palawan and Zamboanga were

connected to the Eurasian plate.

They stirred towards the east and joined togetherthe islands of the Philippines.

During this movement, three major island groupsemerged:

Luzon which covered Luzon upto Samar, Eastern and Central

Mindanao and Zamboanga and WesternMindanao.


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The continental drift caused some volcanicactivities and earthquakes.

It also created trenches of which volcanoes arise.Examples of these can be seen at the eastern partof the country, like Bicol and Leyte.

They were located at the Philippine Seatrench and the East Luzon trough which resultedform the collision of the Philippine Sea plate andthe Pacific plate.

It can also be seen in the western part of thecountry like the volcanoes in Batanes, Tagalog

region, Panay-Negros,Zamboanga-Sulu.

There are also trenches in Manila-Negros-Sulu-Cotabato due to the continent drift ofthe Eurasian plate and the Philippine Sea plate.


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In addition, faults were created.

There were earthquakes because of themovement of the faults.

There were constant earthquakes

that started in Mindanao that ranthrough Leyte, Masbate,and Quezon until it haltedat Cordillera.

The formation of rivers and valleysin Marikina and Central Luzon wereassumed to be the result ofthe convergent plate boundaries.


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South China Sea widen becauseof the aperture in betweenthe Eurasian plate and the Microcontinental Block duringthe early Miocene period.

A major event during the middleMiocene period was thecollision of the Micro continentalBlock of Palawan into the original

islands of the Philippines whichcaused volcanic activitiesin Sulu.


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In the late Miocene period, the volcanic eruptions ceased in the

islands ofSulu but the Pacific and Philippine plates continued tomove.

The northern part of the Manila trench crashed into Taiwan thatcaused the low lands ofLuzon to appear from the ocean.

The Manila Trench reached the Western Mindanao in the last

part of the Miocene period. It was cut-off and became Negros and Cotabato trenches

when Mindoro-Palawan and the Peninsula of Zamboanga werepinned to the original islands of the Philippines.

It was also during this time that the eastern part of the

Philippines sank in the Philippine trench area. This was the start of the formation of the Philippines in its

current location, form and shape.


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The plate tectonics in the Philippines is complex andincludes plate boundaries that are changing rapidly.

Several micro-plates are getting squeezed between twoconvergent plate margins.

Stratigraphic evidence indicates cessation andreactivation of subduction at some trenches.

The currently active volcanoes in the Philippinesdefine two north-south trending arcs.

The scale and type of volcanism varies from

monogenetic cinder cone fields to largestratovolcanoes and calderas.

Composition of volcanic rocks range from tholeiiticbasalt to andesite to shoshonite.

Black triangles = active subduction zones with "teeth"on the over-riding plate, white triangles = inactivesubduction zones with "teeth" on the over-riding plate,

arrows = transform or major strike-slip faults, redtriangles = volcanoes active in the last 10,000 years.

Plates and micro-plates shown in different colors.Based on Divis (1983). Volcanoes from Simkin andSiebert (1994).


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In the west, more steeplyeast-dipping subduction ofthe Eurasian Plate along the560 mile (900 km) lengthof the Manila and Sulutrenches produces a

discontinuous line of activevolcanoes from Taal in thesouth to Iraya in the north.

Volcanism associated withthis subduction zone beganabout 10 million years ago.


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In the east, shallow west-dipping subduction of thePhilippine Plate at the Philippine Trench producesa line of volcanoes from Balut in the south toMayon in the north. Based on Divis (1983).

Volcanoes in an east-west zone across centralLuzon may be associated with a "leaky" transformfault that connects the two subduction zones.

The transform fault is offset to the right by theyounger Philippine Fault. Based on Divis (1983).

The volcanoes of the Philippines are the mostdeadly and costly in the world. Fatalities have been

caused by 13% of the historic eruptions, mostnotably at Taal and Mayon, and 22% of theeruptions caused damage.

Mudflows are more common in the Philippines,compared to other regions, because of heavy rains.Tsunami are more commonly associated witheruptions at the Philippines than in any other

volcanic region. Many of the Holocene volcanoes in the Philippines

have eruptive products that have not been dated.Since the Philippines Institute of Volcanology andSeismology has been established the impacts oferuptions have been greatly reduced.

philippines tectonics

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