Philippine Trench

The Philippine trench is hypothesized to be younger than 8–9 million years old. The central part of the Philippine fault formed during the Plio-Pleistocene times is considered to be an active depression of the Earth's crust. The trench formed from a collision between the Palawan and Zamboanga plates. This caused a change in geological processes creating a subduction zone, that is dropping the ocean floor deeper. though the USGS has recorded many earthquakes with magnitude ≥ 7.2 in the region as shown by the map to the side. Most recently, in 2012 the Philippine Trench experienced an earthquake of Mw 7.6 (the 2012 Samar earthquake). It hit the trench with a hypocenter depth of 34.9 km. Areas adjacent to the subduction zones have experienced large seismic activity. In 1897, northern Samar experienced a Ms 7.3 earthquake while in 1924 southern Mindanao experienced one with a Ms 8.2. == Depth ==

The trench reaches one of the greatest depths in the ocean. Its deepest point is known as Emden Deep and reaches 10,540 meters (34,580 ft or 5,760 fathoms). == Sedimentation ==

Sedimentation of the Philippine trench contains slightly metamorphosed, calc-alkalic, basic, ultrabasic rock and sand grains. The southern area of the trench contains homogeneous blue clay silt and is poor in lime. Sand grains that were also found contained fresh basaltic andesite. The sediments found in the trenches are hypothesized to have been deposited by turbidity currents. A turbidity current is an underwater current that moves rapidly and carries sediment. == Significant quakes ==

This is a list of significant quakes related to the Philippine Trench, which are 7.0+ == Other trenches ==

Other known trenches in the Philippines are: • Manila Trench • East Luzon Trench • Negros Trench • Sulu Trench • Cotabato Trench == References ==