Copahue
Encyclopedia
Copahue is a stratovolcano
on the border between Argentina
and Chile
. There are nine volcanic crater
s along a 2 km (1.2 mi) line, and the eastern summit crater contains a briny, acidic 300 m (1000 ft) wide crater lake
. Twentieth-century eruptions from the crater lake have ejected pyroclastic rock
s and chilled liquid sulfur
fragments.
The modern structure is an elongated shield volcano, with a maximum thickness of 22 kilometers and a minimum of 8 kilometers. There have been at least 6 eruptions within the Holocene
, with the most recent in 2000. The easternmost (and most active) crater contains a crater lake
with a pH ranging between .18 and .30. While it emptied during the 2000 eruption, it has returned to its previous levels.
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
on the border between Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
and Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. There are nine volcanic crater
Volcanic crater
A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth...
s along a 2 km (1.2 mi) line, and the eastern summit crater contains a briny, acidic 300 m (1000 ft) wide crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...
. Twentieth-century eruptions from the crater lake have ejected pyroclastic rock
Pyroclastic rock
Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic...
s and chilled liquid sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
fragments.
Geology and Geography
Copahue sits on a basement of sedimentary and volcanic rocks ranging from the Eocene to the Pliocene. The modern volcano sits in a volcanically active area, with a caldera from the Pliocene, measuring 20 km by 15 km, lying to the east of Copahue. The modern volcano became active roughly 1.2 Ma. The modern caldera formed .6 to .4 Ma, and produced large pyroclastic flows, extending up to 37 kilometers from the volcano.The modern structure is an elongated shield volcano, with a maximum thickness of 22 kilometers and a minimum of 8 kilometers. There have been at least 6 eruptions within the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
, with the most recent in 2000. The easternmost (and most active) crater contains a crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...
with a pH ranging between .18 and .30. While it emptied during the 2000 eruption, it has returned to its previous levels.