Avacha Volcano
Encyclopedia
Avachinsky is an active stratovolcano
on the Kamchatka Peninsula
in the far east of Russia
. It lies within sight of the capital of Kamchatka Krai, Petropavlovsk-Kamchatsky
. Together with neighboring Koryaksky
volcano, it has been designated a Decade Volcano, worthy of particular study in light of its history of explosive eruptions and proximity to populated areas.
Avachinsky's last eruption occurred in 2001. This eruption was tiny compared to the volcano's major Volcanic Explosivity Index
4 eruption in 1945.
, at a point where the Pacific Plate
is sliding underneath the Eurasian Plate
at a rate of about 80 mm/year. A wedge of mantle
material lying between the subducting
Pacific Plate and the overlying Eurasian Plate is the source of dynamic volcanism over the whole Kamchatka Peninsula.
The volcano is one of the most active volcanoes on the Kamchatka Peninsula, and began erupting in the middle to late Pleistocene
era. It has a horseshoe-shaped caldera
, which formed 30-40,000 years ago in a major landslide
which covered an area of 500 km² south of the volcano, underlying the city of Petropavlovsk-Kamchatsky. Reconstruction of a new cone inside the caldera occurred in two major eruption phases, 18,000 and 7,000 years ago.
records the eruption of Avachinsky on June 15, 1779. He refers to Koryaksky
and Avachinsky as Peter and Paul.
s and lahar
s have tended to be directed to the south west by the breached caldera. The most recent large eruption (VEI
=4) occurred in 1945, when about 0.25 km³ of magma
was ejected. The volcano has since had small eruptions in 1991 and 2001.
The volcano continues to experience frequent earthquake
s, and many fumarole
s exist near the summit. The temperature of gases emitted at these fumaroles has been measured at over 400°C. In light of its proximity to Petropavlovsk-Kamchatsky, Avachinsky was designated a Decade Volcano in 1996 as part of the United Nations
' International Decade for Natural Disaster Reduction, together with the nearby Koryaksky
volcano.
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 Kamchatka Peninsula
Kamchatka Peninsula
The Kamchatka Peninsula is a peninsula in the Russian Far East, with an area of . It lies between the Pacific Ocean to the east and the Sea of Okhotsk to the west...
in the far east of Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. It lies within sight of the capital of Kamchatka Krai, Petropavlovsk-Kamchatsky
Petropavlovsk-Kamchatsky
Petropavlovsk-Kamchatsky is the main city and the administrative, industrial, scientific, and cultural center of Kamchatka Krai, Russia. Population: .-History:It was founded by Danish navigator Vitus Bering, in the service of the Russian Navy...
. Together with neighboring Koryaksky
Koryaksky
Koryaksky or Koryakskaya Sopka is a volcano on the Kamchatka Peninsula in the far east of Russia. It lies within sight of Kamchatka Krai's administrative center, Petropavlovsk-Kamchatsky...
volcano, it has been designated a Decade Volcano, worthy of particular study in light of its history of explosive eruptions and proximity to populated areas.
Avachinsky's last eruption occurred in 2001. This eruption was tiny compared to the volcano's major Volcanic Explosivity Index
Volcanic Explosivity Index
The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....
4 eruption in 1945.
Geological history
Avachinsky lies on the Pacific Ring of FirePacific Ring of Fire
The Pacific Ring of Fire is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. In a horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements...
, at a point where the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
is sliding underneath the Eurasian Plate
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
at a rate of about 80 mm/year. A wedge of mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
material lying between the subducting
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
Pacific Plate and the overlying Eurasian Plate is the source of dynamic volcanism over the whole Kamchatka Peninsula.
The volcano is one of the most active volcanoes on the Kamchatka Peninsula, and began erupting in the middle to late Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
era. It has a horseshoe-shaped caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
, which formed 30-40,000 years ago in a major landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
which covered an area of 500 km² south of the volcano, underlying the city of Petropavlovsk-Kamchatsky. Reconstruction of a new cone inside the caldera occurred in two major eruption phases, 18,000 and 7,000 years ago.
Recorded history
In his Journal of Captain Cook's Last Voyage, John LedyardJohn Ledyard
John Ledyard was an American explorer and adventurer.-Early life:Ledyard was born in Groton, Connecticut, the oldest son of John and Abigail Ledyard and the nephew of Continental Army Colonel William Ledyard...
records the eruption of Avachinsky on June 15, 1779. He refers to Koryaksky
Koryaksky
Koryaksky or Koryakskaya Sopka is a volcano on the Kamchatka Peninsula in the far east of Russia. It lies within sight of Kamchatka Krai's administrative center, Petropavlovsk-Kamchatsky...
and Avachinsky as Peter and Paul.
Recent activity
Avachinsky has erupted at least 16 times in recorded history. Eruptions have generally been explosive, and pyroclastic flowPyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...
s and lahar
Lahar
A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley. The term is a shortened version of "berlahar" which originated in the Javanese language of...
s have tended to be directed to the south west by the breached caldera. The most recent large eruption (VEI
Volcanic Explosivity Index
The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....
=4) occurred in 1945, when about 0.25 km³ of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
was ejected. The volcano has since had small eruptions in 1991 and 2001.
The volcano continues to experience frequent earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s, and many fumarole
Fumarole
A fumarole is an opening in a planet's crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The steam is created when superheated water turns to steam as its pressure drops when it emerges from...
s exist near the summit. The temperature of gases emitted at these fumaroles has been measured at over 400°C. In light of its proximity to Petropavlovsk-Kamchatsky, Avachinsky was designated a Decade Volcano in 1996 as part of the United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...
' International Decade for Natural Disaster Reduction, together with the nearby Koryaksky
Koryaksky
Koryaksky or Koryakskaya Sopka is a volcano on the Kamchatka Peninsula in the far east of Russia. It lies within sight of Kamchatka Krai's administrative center, Petropavlovsk-Kamchatsky...
volcano.