Philippine Mobile Belt

The Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian Plate and the Philippine Sea Plate, comprising most of the country of the Philippines. It includes two subduction zones, the Manila Trench to the west and the Philippine Trench to the east, as well as the Philippine Fault System. Within the Belt, a number of crustal blocks or microplates which have been shorn off the adjoining major plates are undergoing massive deformation.[1]

Most segments of the Philippines, including northern Luzon, are part of the Philippine Mobile Belt, which is bounded by the Philippine Sea Plate to the east, the Molucca Sea Collision Zone to the south, Sunda Plate to the southwest, and the South China Sea Basin to the west and north-west.[2] To the north it ends in eastern Taiwan, the zone of active collision between the North Luzon Trough portion of the Luzon Volcanic Arc and South China.[3] The Philippine Mobile Belt has also been called the Philippine Microplate[4] and the Taiwan-Luzon-Mindoro Belt.[5]

PhilippineMobileBelt007
Major physiographic elements of the Philippine Mobile Belt
Puerto Princesa Subterranean River National Park geologic marker
Puerto Princesa Subterranean River National Park marker describing the geologic history of the Philippines

Palawan and Sulu

Although they are part of the Republic of the Philippines, Palawan with the Calamian Islands, plus the Sulu Archipelago with the Zamboanga Peninsula of western Mindanao, are the tops of two protruding north-eastern arms of the Sunda Plate. They are not part of the Philippine Mobile Belt but are in collision with it. The Sulu Trench marks the boundary of the Sulu micro-block with the Sulu Sea basin and the Palawan micro-block. The inactive Palawan Trench marks the subduction boundary between the Palawan microblock and the Spratly Islands plateau of the South China Sea basin.[6] The Palawan/Calamian arm was also known in 1981 as the Palawan block and Palawan microcontinent,[7] and in 1989 as the Palawan Micro-Block.[8]

Boundaries

The Philippine Mobile Belt is bounded on the west by the Manila Trench and its associates the Negros Trench and the Cotabato Trench, which subducts the Sunda Plate under the Philippine Mobile Belt. To the east is the Philippine Trench and its northern associate, the East Luzon Trench which subducts Philippine Sea Plate the Philippine Mobile Belt.[9] The continuity of the Philippine-East Luzon Trench is interrupted and displaced by Benham Plateau on the Philippine Sea Plate,[10] which collided and is still colliding with the Sierra Madre of eastern Luzon.[11]

To the north the Philippine Mobile Belt ends in Taiwan, where accreted portions of the Luzon Arc and Luzon forearc form the eastern Coastal Range and the inland Longitudinal Valley of Taiwan, respectively.[12]

To the south the Philippine Mobile Belt terminates in the Molucca Sea Collision Zone, which is itself part of the elongated zone of convergence extending north through the Philippines into Taiwan. Within the Molucca Sea Collision Zone, the Molucca Sea Plate has been totally subsumed by the arc-arc collision of the Halmahera Arc and the Sangihe Arc of eastern Indonesia.[13]

Regional Geology

The belt's basement rock complex consists of oceanic crust from the Philippine Sea Plate, including ophiolites in North Luzon, or continental crust from the Sunda Plate. On top of which are Cretaceous to Quaternary magmatic arcs. These magmatic arcs are exposed in the western Central Cordillera, and the northern Sierra Madre. The Cagayan River Basin is an intra-arc rift. Subduction of Late Oligocene to Early Miocene South China sea oceanic crust occurs at the Manila Trench. Subduction of Eocene Philippine Sea oceanic crust occurs at the East Luzon Trough - Philippine Trench system. The strike-slip, left lateral fault, Philippine Fault System is associated with the northward movement of the belt.[14]

Collision zones

  • Taiwan: Continent-Arc Collision – 400 km-long island dominated by mountain ranges. Represents an active orogenic belt resulting from the collision of the western edge of the Philippine Sea Plate where the Luzon arc has developed, with the continental margin of Eurasia. Start of collision is associated with the kinematic reorganization of the Philippine Sea Plate 4 Ma involving a change in the direction of its movement from a northerly to a northwesterly motion.
  • Mindoro-Panay: Arc-Continent Collision – Southern termination of the Manila Trench. North Palawan Block enters into collision with the central portion of the Philippine Mobile Belt within Miocene times after cessation of the accretion of South China Sea oceanic crust bet 32 and 17 Ma.
  • Moluccas Sea: Arc-Arc Collision – South of Mindanao Island in the Moluccas Sea. Subducting into 2 directions: to the East and to the West. This double-vergent subduction causes consequently the convergence/collision of the 2 corresponding active volcanic arcs. Start of collision in Upper Miocene. Corresponding arcs, the Sangihe and Halmahera, are presently separated by at least 100 km.

Luzon

The island of Luzon is bisected by the braided N-S trending Philippine Fault System.[15] Luzon is not bisected E-W, and illustrations showing anything similar are erroneous. Northern Luzon is integral with southern Luzon. Any suggestion that Northern Luzon is not part of the Philippine Mobile Belt is not borne out by the detailed fault mapping of Pinet and Stephan (1989),[16] and others. A common tectonic plate illustration for the Philippines[17] is incorrect in this regard.

Collage of 17 principal blocks

The composition of the Philippine Mobile Belt is generally interpreted as a collage of a large variety of blocks or terrane of diverse origin amalgamated before collision with the Eurasian margin.[18] Seven principal blocks have been identified in Luzon: the Sierra Madre Oriental, Angat, Zambales, Central Cordillera of Luzon, Bicol and Catanduanes Island blocks. In the Central Philippines four principal blocks have been identified: Panay, Mindoro, Cebu and Bohol. In Mindanao six principal blocks have been identified: Pacific Cordillera, Surigao, Pujada peninsular, Central Cordillera of Mindanao, Daguma range and Zamboanga.[19]

Well-known micro-continental blocks

Magmatic arcs

Ancient arcs

In Luzon, the Middle Oligocene to Late Miocene age of the arc is well constrained stratigraphically as well as radiometrically. Most of the intrusive rocks are dioritic in composition, although alkali rocks also occur. In the Central Cordillera of Luzon, intrusive rocks include Paleogene rocks related to an ancient arc and Neogene intrusive and volcanic rocks related to eastward subduction from the Manila Trench.

In Visayas, oldest known magmatic rocks in the Philippines are found in Cebu Island, where dioritic rocks have been dated at Lower Cretaceous (Walther and others, 1981), similar rocks have been recognized in neighboring Bohol Island.

In Mindanao, interpretation of the age of these rocks is further complicated by their petrographic diversity. Sajona and others (1993) analyzed Pliocene-Pleistocene adakitic rocks in Zamboanga Peninsula and mention a possible association with activity along the Philippine Fault in Surigao and northern Davao.

Active arcs

The distribution of Philippine Pliocene-Quaternary volcanoes generally reflects the activity along subduction zones presently bounding the archipelago.

Sedimentary Basins

The archipelago has 16 sedimentary basins formed by tectonic processes. Here are the following sedimentary basins:[20]

  • Luzon
    • Bicol Shelf
    • Cagayan Valley Basin
    • Central Luzon Basin
    • Ilocos Trough
    • Mindoro-Cuyo Basin
    • East Palawan Basin
    • Northwest Palawan Basin
    • Reed Bank Basin
    • Southeast Luzon Basin
    • Southwest Palawan Basin
    • West Luzon Basin
  • Visayas
    • Visayan Basin (or in Luzon)
    • West Masbate-Iloilo Basin
  • Mindanao
    • Agusan-Davao Basin
    • Cotabato Basin
    • Sulu Sea Basin

See also

References

  1. ^ Galgana, G.A.; Hamburger, M.W.; McCaffrey, R.; Bacolcol, T.C.; Aurelio, M.A. (1 December 2007). "Modeling the Philippine Mobile Belt: Tectonic blocks in a deforming plate boundary zone". AGU Fall Meeting Abstracts. 2007: G21C–0670. Bibcode:2007AGUFM.G21C0670G.
  2. ^ Rangin and Pubellier (1990) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p140 ff
  3. ^ Clift, Schouten and Draut (2003) in Intra-Oceanic Subduction Systems: Tectonic and Magmatic Processes, ISBN 1-86239-147-5 p84-86
  4. ^ Hashimoto, M, ed., (1981) Accretion Tectonics in the Circum-Pacific Regions, ISBN 90-277-1561-0 p302
  5. ^ Nicolas Pinet and Jean Francois Stephan (1989) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p165
  6. ^ Rangin and Pubellier (1990) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p148
  7. ^ Hashimoto, M, ed., (1981) Accretion Tectonics in the Circum-Pacific Regions, ISBN 90-277-1561-0 p303
  8. ^ Nicolas Pinet and Jean Francois Stephan (1989) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p167 Fig 1, p175, p177
  9. ^ Hashimoto, M, ed., (1981) Accretion Tectonics in the Circum-Pacific Regions, ISBN 90-277-1561-0 p299
  10. ^ Deschamps and Lallemand (2003) in Intra-Oceanic Subduction Systems: Tectonic and Magmatic Processes ISBN 1-86239-147-5 p165
  11. ^ Rangin and Pubellier (1990) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4, p149
  12. ^ Clift, Schouten and Draut (2003) in Intra-Oceanic Subduction Systems: Tectonic and Magmatic Processes, ISBN 1-86239-147-5 p86
  13. ^ Macpherson, Forde, Hall and Thirlwall (2003) in Intra-Oceanic Subduction Systems: Tectonic and Magmatic Processes, ISBN 1-86239-147-5 p208
  14. ^ Polve, Mireille; Maury, Rene; Jego, Sebastien; Bellon, Jerve; Margoum, Ahmed; Yumul, Graciano; Payot, Betchaida; Tamayo, Rodolfo; Cotten, Joseph (2007). "Temporal Geochemical Evolution of Neogene Magmatism in the Baguio Gold-Copper Mining District (Northern Luzon, Philippines)". Resource Geology. 57 (2): 197–218. doi:10.1111/j.1751-3928.2007.00017.x.
  15. ^ Nicolas Pinet and Jean Francois Stephan (1989) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p170
  16. ^ Nicolas Pinet and Jean Francois Stephan (1989) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p167 Fig 1
  17. ^ File:Philippine Sea plate.JPG
  18. ^ Rangin and Pubellier (1990) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p149
  19. ^ Rangin and Pubellier (1990) in Tectonics of Circum-Pacific Continental Margins ISBN 90-6764-132-4 p148 fig 4
  20. ^ "::.......CCOP EPF..." www.ccop.or.th. Retrieved 20 April 2018.
1976 Moro Gulf earthquake

The 1976 Moro Gulf earthquake and tsunami took place on August 17 at 00:11 local time near the islands of Mindanao and Sulu, in the Philippines. Its magnitude was calculated as being as high as 8.0 on the moment magnitude scale.

2012 Samar earthquake

An earthquake off the coast of Samar occurred on August 31, 2012, at 20:47 local time (12:47 UTC) in the Philippines. The populated islands of Visayas were struck by an earthquake of magnitude Mw 7.6. The earthquake has a depth of 45 km (27.9 miles). A tsunami warning was announced within the Pacific area and was later lifted after two hours. The Philippine archipelago is located in the Pacific Ring of Fire, where earthquakes and volcanic activity are common.

Geography of the Philippines

The Philippines is an archipelago that comprises 7,641 islands with a total land area of 300,000 square kilometers (115,831 sq mi). It is the world's 5th largest island country. The eleven largest islands contain 95% of the total land area. The largest of these islands is Luzon at about 105,000 square kilometers (40,541 sq mi). The next largest island is Mindanao at about 95,000 square kilometers (36,680 sq mi). The archipelago is around 800 kilometers (500 mi) from the Asian mainland and is located between Taiwan and Borneo.

The Philippine archipelago is divided into three island groups: Luzon, Visayas, and Mindanao. The Luzon islands include Luzon itself, Palawan, Mindoro, Marinduque, Masbate, Romblon, Catanduanes, Batanes and Polilio. The Visayas is the group of islands in the central Philippines, the largest of which are: Panay, Negros, Cebu, Bohol, Leyte, Samar, Siquijor, Biliran and Guimaras. The Mindanao islands include Mindanao itself, Dinagat, Siargao, Camiguin, Samal, plus the Sulu Archipelago, composed primarily of Basilan, Sulu, and Tawi-Tawi.

Halmahera Plate

Halmahera Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.

Huadong Valley

The Huadong Valley or Hualien–Taitung Valley (Chinese: 花東縱谷; pinyin: Huādōng Zònggǔ; Wade–Giles: Hua1-tung1 Tsung4-ku3), also known as East Rift Valley or the Longitudinal Valley, is a long and narrow valley located between the Central Mountain Range and the Coastal Mountain Range. It is also recognized as a plain area which stretches for about 180 kilometers near the eastern coast of Taiwan, passes from Hualien City at the north to Taitung City at the south. It was called Nakasendō Plain (中仙道平野, Nakasendō Heiya) or simply Nakasendō during the era of Japanese rule.The valley is believed to be part of the northern terminus of the Philippine Mobile Belt, a complex collection of tectonic plate fragments and volcanic intrusions. There are three large river systems flowing through this valley, including the Hualian, Xiugulan and Beinan Rivers, all of which flow into the Pacific Ocean.

The Huadong Highway, a section of Provincial Highway No. 9, runs the entire length of the valley from north to south.

Intermontane Belt

The Intermontane Belt is a physiogeological region in the Pacific Northwest of North America, stretching from northern Washington into British Columbia, Yukon, and Alaska. It comprises rolling hills, high plateaus and deeply cut valleys. The rocks in the belt have very little similarities with the North American continent.

Intermontane Plate

The Intermontane Plate was an ancient oceanic tectonic plate that lay on the west coast of North America about 195 million years ago. The Intermontane Plate was surrounded by a chain of volcanic islands called the Intermontane Islands, which had been accumulating as a volcanic chain in the Pacific Ocean since the Triassic period, beginning around 245 million years ago. The volcanism records yet another subduction zone. Beneath the far edge of the Intermontane microplate, another plate called the Insular Plate was sinking. This arrangement with two parallel subduction zones is unusual. The modern Philippine Islands are located on the Philippine Mobile Belt, one of the few places on Earth where twin subduction zones exist today. Geologists call the ocean between the Intermontane islands and North America the Slide Mountain Ocean. The name comes from the Slide Mountain Terrane, a region made of rocks from the floor of the ancient ocean.

List of Ultras of the Philippines

This is a list of all the Ultra prominent peaks (with topographic prominence greater than 1,500 metres) in the Philippines.

List of rivers of the Philippines

This is a list of rivers in the Philippines.

The country's longest river is the Cagayan River, with a length of 505 kilometres (314 mi), followed by the Mindanao River and Agusan River, with respective lengths of 373 kilometres (232 mi) and 349 kilometres (217 mi). With an area of 27,753 square kilometres (10,715 sq mi), the Cagayan River has the largest drainage basin, followed by the Mindanao (23,169 km2 or 8,946 sq mi), Agusan (11,937 km2 or 4,609 sq mi), and Pampanga Rivers (10,434 km2 or 4,029 sq mi).

List of tectonic plate interactions

Tectonic plate interactions are of three different basic types:

Divergent boundaries are areas where plates move away from each other, forming either mid-oceanic ridges or rift valleys. These are also known as constructive boundaries.

Convergent boundaries are areas where plates move toward each other and collide. These are also known as compressional or destructive boundaries.

Subduction zones occur where an oceanic plate meets a continental plate and is pushed underneath it. Subduction zones are marked by oceanic trenches. The descending end of the oceanic plate melts and creates pressure in the mantle, causing volcanoes to form.

Obduction occurs when the continental plate is pushed under the oceanic plate, but this is unusual as the relative densities of the tectonic plates favours subduction of the oceanic plate. This causes the oceanic plate to buckle and usually results in a new mid ocean ridge forming and turning the obduction into subduction

Orogenic belts occur where two continental plates collide and push upwards to form large mountain ranges. These are also known as collision boundaries.

Transform boundaries occur when two plates grind past each other with only limited convergent or divergent activity.

List of tectonic plates

This is a list of tectonic plates on the Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks.

Manila Trench

The Manila Trench is an oceanic trench in the Pacific Ocean, located west of the islands of Luzon and Mindoro in the Philippines. The trench reaches a depth of about 5,400 metres (17,700 ft), in contrast with the average depth of the South China Sea of about 1,500 metres (4,900 ft). It is created by subduction, in which the Sunda Plate (part of Eurasian Plate) is subducting under the Philippine Mobile Belt, producing this almost N-S trending trench. The convergent boundary is terminated to the north by the Taiwan collision zone, and to the south by the Mindoro terrane (Sulu-Palawan block colliding with SW Luzon). It is an area pervaded by negative gravity anomalies.The Manila Trench is associated with frequent earthquakes, and the subduction zone is responsible for the belt of volcanoes on the west side of the Philippine island of Luzon, which includes Mount Pinatubo.

Convergence between the Philippine Mobile Belt and the Sunda Plate have been estimated using GPS measurements, and this value ranges from ~ 50+ mm/yr in Taiwan, to 100 mm/yr near N. Luzon, and ~ 50 mm/yr near Zambales and ~20+mm/yr near Mindoro island. Plate locking between the Sunda Plate and Luzon is about 1% coupled, almost unlocked as determined by elastic block models, suggesting that the trench absorbs the Philippine Mobile Belt-Eurasian Plate convergence.

Mindoro Block

The Mindoro block is a microcontinental block located in the Philippine Mobile Belt and the east side of North Palawan Block. It has comprises a metamorphic basement (Mindoro Metamorphics of Teves, 1953) of unknown but probably pre-late cretaceous age, overlain locally by upper cretaceous basalts (Karig, 1983), and more regionally succeeded by a probable upper eocene sequence of basinal clastic rocks, plus local basalt intercalations and carbonates. These rocks are exposed over a broad area of northern and west-central Mindoro as well as on the Lubang Islands in Verde Island Passage. The Mindoro block is bounded on the west by the Mindoro Suture Zone, and on the north by the Verde Passage Suture (Karig, 1983), which separates it from the Zambales Ophiolite terrane of Luzon. The eastern terrane boundary may be the East Mindoro Fault Zone, a probable transcurrent boundary that has not yet been studied, but which displays evidence of recent activity (Karig, 1983). Late Miocene and Pliocene basinal clastic strata lie east of this fault zone (Metal Mining Agency, 1982), but it is not known if subjacent rocks are related to rocks of the Mindoro block, or if they are part of a third terrane on Mindoro.

Molucca Sea Collision Zone

The Molucca Sea Collision Zone is postulated by paleogeologists to explain the tectonics of the area based on the Molucca Sea in Indonesia, and adjacent involved areas.

Philippine Fault System

The Philippine Fault System is a major inter-related system of faults throughout the whole of the Philippine Archipelago, primarily caused by tectonic forces compressing the Philippines into what geophysicists call the Philippine Mobile Belt.

Philippine Sea Plate

The Philippine Sea Plate or the Philippine Plate is a tectonic plate comprising oceanic lithosphere that lies beneath the Philippine Sea, to the east of the Philippines. Most segments of the Philippines, including northern Luzon, are part of the Philippine Mobile Belt, which is geologically and tectonically separate from the Philippine Sea Plate.

Philippine Sea plate is bordered mostly by convergent boundaries:

To the north, the Philippine Sea Plate meets the Okhotsk Plate at the Nankai Trough. The Philippine Sea Plate, the Amurian Plate, and the Okhotsk Plate meet at Mount Fuji in Japan. The thickened crust of the Izu-Bonin-Mariana arc colliding with Japan constitutes the Izu Collision Zone.

To the east, Philippine Sea Plate meets the Pacific Plate, subducting at the Izu-Ogasawara Trench. The east of the plate includes the Izu-Ogasawara (Bonin) and the Mariana Islands, forming the Izu-Bonin-Mariana Arc system. There is also a divergent boundary between the Philippine Sea Plate and the small Mariana Plate which carries the Mariana Islands.

To the south, the Philippine Sea Plate is bounded by the Caroline Plate and Bird's Head Plate.

To the west, the Philippine Sea Plate subducts under the Philippine Mobile Belt at the Philippine Trench and the East Luzon Trench. (The adjacent rendition of Prof. Peter Bird's map is inaccurate in this respect.)

To the northwest, the Philippine Sea Plate meets Taiwan and the Nansei islands on the Okinawa Plate, and southern Japan on the Amurian Plate.

Sangihe Plate

Sangihe Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.

Sunda Plate

The Sunda Plate is a minor tectonic plate straddling the equator in the eastern hemisphere on which the majority of Southeast Asia is located.The Sunda Plate was formerly considered a part of the Eurasian Plate, but GPS measurements have confirmed its independent movement at 10 mm/yr eastward relative to Eurasia.

Taiwanese hot springs

Taiwan is part of the collision zone between the Yangtze Plate and Philippine Sea Plate. Eastern and southern Taiwan are the northern end of the Philippine Mobile Belt.

Located next to an oceanic trench and volcanic system in a tectonic collision zone, Taiwan has evolved a unique environment that produces high-temperature springs with crystal-clear water, usually both clean and safe to drink. These hot springs are not only clean and potable but also commonly used for spas and resorts.

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