Mount Spurr (
Dena'ina: ''K'idazq'eni'') is a
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 ...
in the
Aleutian Arc
The Aleutian Arc is a large volcanic arc of islands extending from the Southwest tip of the U.S. state of Alaska to the Kamchatka Peninsula of the Russian Federation.
It consists of a number of active and dormant volcanoes that have formed as a ...
of
Alaska
Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
, named after
United States Geological Survey
The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...
geologist and explorer
Josiah Edward Spurr
Josiah Edward Spurr (1870–1950) was an American geologist, explorer, and author.
Born in Gloucester, Massachusetts, he was considered something of a failure as a youth, unsuited for the family fishing business, since on a voyage he invariably ...
, who led an expedition to the area in 1898. The
Alaska Volcano Observatory
The Alaska Volcano Observatory (AVO) is a joint program of the United States Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surv ...
(AVO) rates Mount Spurr as
Level of Concern Color Code Yellow.
[ The mountain is known aboriginally by the Dena'ina Athabascan name ''K'idazq'eni'', literally 'that which is burning inside'.]volcano
A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most oft ...
of the Aleutian Arc, is a large stratocone at the center of a roughly horseshoe-shaped 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 south. The volcano lies west of Anchorage
Anchorage, officially the Municipality of Anchorage, is the most populous city in the U.S. state of Alaska. With a population of 291,247 at the 2020 census, it contains nearly 40 percent of the state's population. The Anchorage metropolita ...
and northeast of Chakachamna Lake. The caldera was formed by a late-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 ...
or early 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 ...
sector collapse and associated pyroclastic flows that destroyed an ancestral Spurr volcano. The debris avalanche traveled more than to the southeast, and the resulting deposit contains blocks as large as in diameter. Several ice-carved post-caldera domes lie in the caldera. Mount Spurr is the highest of the post-caldera. The regrown summit peak of Spurr experienced a heating event in 2004 which created a small crater lake. By 2008, the summit crater had cooled enough to have begun to have accumulated significant amounts of snow again. The youngest post-caldera dome, Crater Peak (), formed at the breached southern end of the caldera about south of Spurr, has been the source of about 40 identified Holocene tephra
Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism.
Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
layers. Spurr's two historical eruptions, from Crater Peak in 1953 and 1992, deposited ash on the city of Anchorage. Crater Peak has a summit crater that is itself slightly breached along the south rim; the north wall of the crater exposes the truncated remains of an older dome or lava lake
Lava lakes are large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression. The term is used to describe both lava lakes that are wholly or partly molten and those that are solidified (sometim ...
. Before the 1992 eruption, a small crater lake occupied the bottom of Crater Peak's crater.
As with other Alaskan volcanoes, the proximity of Spurr to major trans-Pacific aviation routes means that an eruption of this volcano could significantly disrupt air travel. Volcanic ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...
can cause jet engines to fail.
Recent activity
On July 26, 2004, the AVO raised the "Color Concern Code" at Spurr from green to yellow due to an increasing number of earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
s. Earthquakes beneath a volcano may indicate the movement of magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...
preceding a volcanic eruption
A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior h ...
, but the earthquakes might also die out without an eruption. In the first week of August 2004, the AVO reported the presence of a collapse pit, filled with water forming a new crater lake, in the ice and snow cover on the summit. This lake may have been caused by an increase in heat flow through the summit lava dome.
On May 3, 2005, a debris flow was observed in webcam images, as well as by a nearby pilot. A subsequent overflight revealed that much of the sitting pond within the melt hole had drained away, leaving a cauldron, and the color of concern was lowered back to green on February 21, 2006.
Gallery
File:Eruption column from Crater Peak vent.jpg, Eruption column from Crater Peak vent in 1992
File:Mountains to the west of Ancorage (5452885646).jpg, Mount Spurr (center) and Mount Chichantna (upper right) from east
See also
* Mount Chichantna
References
External links
Volcano World article about Spurr
Mount Spurr Webcam
{{DEFAULTSORT:Spurr, Mount
Volcanoes of Kenai Peninsula Borough, Alaska
Mountains of Kenai Peninsula Borough, Alaska
Three-thousanders of the United States
Stratovolcanoes of Alaska
Subduction volcanoes
Active volcanoes
Volcanic crater lakes
20th-century volcanic events
Calderas of Alaska