Mount Natib is a dormant

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

and

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

complex in the

Zambales Mountains The Zambales Mountains is a mountain range in western Luzon. The mountains spread along a north-south axis, separating Luzon's central plain from the South China Sea. The range extends into five Provinces of the Philippines, provinces: Zambales, ...

on western

Luzon Luzon ( , ) is the largest and most populous List of islands in the Philippines, island in the Philippines. Located in the northern portion of the List of islands of the Philippines, Philippine archipelago, it is the economic and political ce ...

Island of the Philippines. Occupying the northern portion of the

Bataan Peninsula Bataan (, , , ; ) , officially the Province of Bataan, is a Provinces of the Philippines, province in the Central Luzon Regions of the Philippines, region of the Philippines. Its capital is the city of Balanga, Bataan, Balanga while Mariveles, ...

, the mountain and adjacent surrounding is a

protected area Protected areas or conservation areas are locations which receive protection because of their recognized natural or cultural values. Protected areas are those areas in which human presence or the exploitation of natural resources (e.g. firewood ...

first declared as the Bataan National Park in 1945.Mt. Natib"
. Bataan...Raging Peninsula. Retrieved on 2012-02-21.

Physical features

Mount Natib is a

type of volcano topped by a acorn-shaped Natib

Caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

that is open to the northwest. East of its caldera is the smaller wide Pasukulan Caldera. The highest peak of Mount Natib has an elevation of asl and is at the point of convergence of the two calderas. The caldera complex has an overall base diameter of .

Volcanic activity

There are no historical eruptions within the Natib caldera complex. Studies in 1991 (Panum and Rayem) indicate that the last eruptive activity was probably

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

to upper

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. An earlier study in 1971 (Ebasco Services) dated the eruptive products between 69,000 +/- 27,000 years old. A recent study by Dr. Kevin Rodolfo of the Department of Earth and Environmental Sciences at the

University of Illinois at Chicago The University of Illinois Chicago (UIC) is a public research university in Chicago, Illinois, United States. Its campus is in the Near West Side community area, adjacent to the Chicago Loop. The second campus established under the Universi ...

, had Mount Natib's latest eruption between 11,000 and 18,000 years ago after studying a prehistoric

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...

from the volcano that entered

Subic Bay Subic Bay is a bay on the west coast of the island of Luzon in the Philippines, about northwest of Manila Bay. An extension of the South China Sea, its shores were formerly the site of a major United States Navy facility, U.S. Naval Base Subi ...

Zambales Zambales, officially the Province of Zambales (; ; ; ; ), is a Provinces of the Philippines, province in the Philippines located in the Central Luzon Regions of the Philippines, region. Its capital is Iba, Zambales, Iba, which is located in t ...

province. Current activity on Natib is through five thermal areas. The

hot spring A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...

s in the Natib

are Asin, Mamot, Tigulangin, Uyong, and Paipit springs. The hot springs have temperatures ranging from 30-56 °C, with low flows, and a neutral to slightly alkaline water discharge. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) lists Mount Natib as a potentially active volcano."Natib"
. Philippine Institute of Volcanology and Seismology. Retrieved on 2012-02-21.

Geology

The rocks found on Natib are predominantly

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

hornblende Hornblende is a complex silicate minerals#Inosilicates, inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common ...

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

, trending to

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...

flows and dacitic tuffs, which are similar to Mount Mariveles, the southern half of the Bataan Peninsula. Natib is part of the Western Bataan Lineament

volcanic belt A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields or volcanic systems. Volcanic belts are found above zones of unusually high temperature () where magma is created ...

, which includes the active

Mount Pinatubo Mount Pinatubo is an active stratovolcano in the Zambales Mountains in Luzon in the Philippines. Located on the tripoint of Zambales, Tarlac and Pampanga provinces, most people were unaware of its eruptive history before the pre-eruption volc ...

."Pinatubo Volcano"
. Philippine Institute of Volcanology and Seismology. Retrieved on 2012-02-21.

References

External links

Philippine Institute of Volcanology and Seismology (PHIVOLCS), Natib pageSmithsonian Institution's Global Volcanism Program, Natib page
{{Volcanoes of the Philippines Natib Natib Natib Natib Landforms of Bataan Natib Natib Pleistocene stratovolcanoes Zambales Mountains

Physical features

Volcanic activity

Geology

See also

References

External links