The Pacific Ring of Fire (see
below)
Tectonic plates of the world.
The
Pacific Ring of Fire (or just
The Ring of Fire) is an area where a large number of
earthquakes and
volcanic eruptions occur in the basin of the
Pacific Ocean. In a 40,000 km (25,000 mi) horseshoe shape, it is associated with a nearly continuous series of
oceanic trenches,
volcanic arcs, and
volcanic belts and/or plate movements. The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and
dormant volcanoes.
[1] It is sometimes called the
circum-Pacific belt or the
circum-Pacific seismic belt.
About 90%
[2] of the world's earthquakes and 81%
[3]
of the world's largest earthquakes occur along the Ring of Fire. The
next most seismic region (5–6% of earthquakes and 17% of the world's
largest earthquakes) is the
Alpide belt, which extends from
Java to
Sumatra through the
Himalayas, the
Mediterranean, and out into the
Atlantic. The
Mid-Atlantic Ridge is the third most prominent earthquake belt.
[4][5]
The Ring of Fire is a direct result of
plate tectonics and the movement and collisions of
lithospheric plates.
[6] The eastern section of the ring is the result of the
Nazca Plate and the
Cocos Plate being
subducted beneath the westward moving
South American Plate. The
Cocos Plate is being subducted beneath the
Caribbean Plate, in
Central America. A portion of the
Pacific Plate along with the small
Juan de Fuca Plate are being subducted beneath the
North American Plate. Along the northern portion the northwestward moving Pacific plate is being subducted beneath the
Aleutian Islands arc. Further west the Pacific plate is being subducted along the
Kamchatka Peninsula arcs on south past
Japan. The southern portion is more complex with a number of smaller tectonic plates in collision with the Pacific plate from the
Mariana Islands, the
Philippines,
Bougainville,
Tonga, and
New Zealand; this portion excludes
Australia, since it lies in the center of its tectonic plate.
Indonesia lies between the
Ring of Fire along the northeastern islands adjacent to and including
New Guinea and the
Alpide belt along the south and west from Sumatra, Java,
Bali,
Flores, and
Timor. The famous and very active
San Andreas Fault zone of
California is a
transform fault which offsets a portion of the
East Pacific Rise under southwestern
United States and
Mexico. The motion of the fault generates numerous small earthquakes, at multiple times a day, most of which are too small to be felt.
[7][8] The active
Queen Charlotte Fault on the west coast of the
Haida Gwaii,
British Columbia,
Canada, has generated three large
earthquakes during the 20th century: a
magnitude 7 event in 1929, a magnitude 8.1 occurred in 1949 (Canada's largest recorded earthquake) and a magnitude 7.4 in 1970.
[9]
Andes
Chile
Earthquake activity in Chile is related to
subduction of the
Nazca Plate to the east. Chile notably holds the record for the
largest earthquake ever recorded, the
1960 Valdivia earthquake.
Villarrica, one of
Chile's most active volcanoes, rises above
Villarrica Lake and the town of
Villarrica. It is the westernmost of three large
stratovolcanoes that trend perpendicular to the Andean chain. A 6-km wide
caldera formed during the late
Pleistocene, >0.9 million years ago.
A 2-km-wide postglacial caldera is located at the base of the
presently active, dominantly basaltic-to-andesitic cone at the NW margin
of the Pleistocene caldera. About 25 scoria cones dot Villarica's
flanks.
Plinian eruptions and
pyroclastic flows
have been produced during the Holocene from this dominantly basaltic
volcano, but historical eruptions have consisted largely of
mild-to-moderate explosive activity with occasional lava effusion.
Lahars from the glacier-covered volcanos have damaged towns on its flanks.
In 2008, Chile experienced two volcanic eruptions, the first one from
Llaima Volcano (January 1) and
Chaitén Volcano (May 1). More recently, an 8.8-magnitude earthquake struck central Chile on February 27, 2010 (
2010 Chile earthquake).
[10]
Bolivia
The country of
Bolivia hosts numerous active and extinct
volcanoes across its territory. The active volcanoes are located in western Bolivia making up the
Cordillera Occidental, the western limit of the
Altiplano plateau. Many of the active volcanoes are international mountains shared with
Chile. All
Cenozoic volcanoes of Bolivia are part of the Central Volcanic Zone (CVZ) of the
Andean Volcanic Belt that results due to processes involved in the
subduction of
Nazca Plate under the
South American Plate. The Central Volcanic Zone is a major upper
Cenozoic volcanic province.
[11] Apart from Andean volcanoes the
geology of Bolivia host the remants of ancient volcanoes around the
Precambrian Guaporé Shield in the eastern part of the country.
Central America
Costa Rica
A powerful, magnitude-7.6 earthquake shook Costa Rica and a wide
swath of Central America. The quake struck at 8:42 a.m. (10:42 a.m. EDT;
1442 GMT) 09/05/2012.
North American Cordillera
Mexico
Volcanoes of Mexico are related to
subduction of the
Cocos and
Rivera plates to the east, which has produced large
explosive eruptions. Most active volcanoes in Mexico occur in the
Trans-Mexican Volcanic Belt,
which extends 900 kilometres (559 mi) from west to east across
central-southern Mexico. A few other active volcanoes in northern Mexico
are related to
extensional tectonics of the
Basin and Range Province, which split the Baja California peninsula from the mainland.
[12] Popocatépetl lies in the eastern half of the Trans-Mexican Volcanic Belt, which is the second highest peak in Mexico after the
Pico de Orizaba.
It is one of most active volcanoes in Mexico, having had more than 20
major eruptions since the arrival of the Spanish in 1519. The 1982
eruption of
El Chichón killed about 2,000 people who lived near the volcano. It created a 1 kilometre (1 mi) wide
caldera that filled with an
acidic crater lake. Prior to 2000, this relatively unknown volcano was heavily forested and of no greater height than adjacent non-volcanic peaks.
[12]
United States
In the western
United States lies the
Cascade Volcanic Arc. It includes nearly 20 major volcanoes, among a total of over 4,000 separate volcanic vents including numerous
stratovolcanoes,
shield volcanoes,
lava domes, and
cinder cones, along with a few isolated examples of rarer volcanic forms such as
tuyas.
Volcanism in the arc began about 37 million years ago, however, most of
the present-day Cascade volcanoes are less than 2,000,000 years old,
and the highest peaks are less than 100,000 years old. It formed by
subduction of the
Gorda and
Juan de Fuca plates at the
Cascadia subduction zone. This is a 680 mi (1,090 km) long
fault, running 50 mi (80 km) off the west-coast of the
Pacific Northwest from
northern California to
Vancouver Island,
British Columbia. The plates move at a relative rate of over 0.4 inches (10 mm) per year at a somewhat oblique angle to the
subduction zone.
Because of the very large fault area, the Cascadia subduction zone
can produce very large earthquakes, magnitude 9.0 or greater, if rupture
occurred over its whole area. When the "locked" zone stores energy for
an earthquake, the "transition" zone, although somewhat plastic, can
rupture. Thermal and deformation studies indicate that the locked zone
is fully locked for 60 kilometers (about 40 miles) down-dip from the
deformation front. Further down-dip, there is a transition from fully
locked to
aseismic sliding.
Unlike most subduction zones worldwide, there is no
oceanic trench present along the
continental margin in
Cascadia. Instead,
terranes and the
accretionary wedge
have been uplifted to form a series of coast ranges and exotic
mountains. A high rate of sedimentation from the outflow of the three
major rivers (
Fraser River,
Columbia River, and
Klamath River)
which cross the Cascade Range contributes to further obscuring the
presence of a trench. However, in common with most other subduction
zones, the outer margin is slowly being compressed, similar to a giant
spring.
When the stored energy is suddenly released by slippage across the
fault at irregular intervals, the Cascadia subduction zone can create
very large
earthquakes such as the
magnitude 9
Cascadia earthquake of 1700.
Geological evidence indicates that great earthquakes may have occurred
at least seven times in the last 3,500 years, suggesting a return time
of 400 to 600 years. There is also evidence of accompanying tsunamis
with every earthquake, as the prime reason they know of these
earthquakes is through "scars" the tsunami left on the coast, and
through
Japanese records (tsunami waves can travel across the Pacific).
The
1980 eruption of Mount St. Helens was the most significant to occur in the contiguous 48
U.S. states in recorded history (
VEI = 5, 0.3 cu mi, 1.2 km
3 of material erupted), exceeding the destructive power and volume of material released by the 1915 eruption of
California's
Lassen Peak. The eruption was preceded by a two-month series of
earthquakes and
steam-venting episodes, caused by an injection of
magma at shallow depth below the mountain that created a huge bulge and a fracture system on
Mount St. Helens'
north slope. An earthquake at 8:32 a.m. on May 18, 1980, caused the
entire weakened north face to slide away, suddenly exposing the partly
molten, gas- and
steam-rich
rock in the volcano to lower pressure. The rock responded by exploding into a very hot mix of pulverized
lava and older rock that sped toward
Spirit Lake so fast that it quickly passed the avalanching north face.
Alaska is known for its seismic and volcanic activity, holding the record for the second
largest earthquake in the world the
Good Friday Earthquake, and having more than 50 volcanoes which have erupted since about 1760.
[13] Volcanoes can be found not only in the mainland but also in the
Aleutian Islands.
The most recent activity in the American portion of the Ring of Fire occurred in early 2009 when
Mount Redoubt in Alaska became active and finally erupted late in the evening of March 22. The eruption ended in May 2009.
Canada
British Columbia and
Yukon are home to a vast region of volcanoes and volcanic activity in the Pacific Ring of Fire.
[14] Several mountains that many British Columbians look at every day are
dormant volcanoes. Most of them have erupted during the
Pleistocene and
Holocene. Although none of Canada's volcanoes are currently erupting, several volcanoes,
volcanic fields and volcanic centers are considered potentially active.
[15] There are
hot springs at some volcanoes while 10 volcanoes in British Columbia appear related to seismic activity since 1975, including: the
Silverthrone Caldera,
Mount Meager,
Wells Gray-Clearwater volcanic field,
Mount Garibaldi,
Mount Cayley,
Castle Rock,
The Volcano,
Mount Edziza,
Hoodoo Mountain,
Crow Lagoon and
Nazko Cone.
[16] The volcanoes are grouped into five
volcanic belts with different tectonic settings.
The
Northern Cordilleran Volcanic Province
(sometimes known as the Stikine Volcanic Belt) is the most active
volcanic region in Canada. It formed due to extensional cracking,
faulting and
rifting of the North American Plate, as the Pacific Plate grinds and slides past the
Queen Charlotte Fault, unlike subduction that produces the volcanoes in Japan, Philippines and Indonesia. The region has
Canada's largest volcanoes,
[14] much larger than the minor
stratovolcanoes found in the Canadian portion of the
Cascade Volcanic Arc.
[14] Several eruptions are known to have occurred within the last 400 years.
Mount Edziza is a huge volcanic complex that erupted several times in the past several thousand of years, which has formed several
cinder cones and
lava flows. The complex comprises the
Mount Edziza Plateau, a large
volcanic plateau (65 kilometers long and 20 kilometers wide) made of predominantly basaltic lava flows with four large
stratovolcanoes built on top of the plateau. The associated
lava domes and
satellite cones were constructed over the past 7.5 million years during five magmatic cycles beginning with eruption of
alkali basalts and ending with
felsic and basaltic eruptions as late as 1,340 years ago. The blocky lava flows still maintain their original forms.
Hoodoo Mountain is a
tuya in northwestern British Columbia, which has had several periods of
subglacial eruptions.
The oldest eruptions occurred about 100,000 years ago and the most
recent being about 7000 years ago. Hoodoo Mountain is also considered
active and could erupt in the future. The nearby
Tseax Cone and
The Volcano produced some of Canada's youngest lava flows, that are about 150 years old.
Canada's worst known geophysical disaster came from the
Tseax Cone during the 18th century at the southernmost end of the
volcanic belt. The eruption produced a 22.5 km long lava flow, destroying the
Nisga'a villages and the death of at least 2000 Nisga'a people by
volcanic gases and poisonous smoke. The
Nass River valley was inundated by the lava flows and contains abundant tree molds and
lava tubes. The event happened at the same time with the arrival of the first
European explorers to penetrate the uncharted coastal waters of northern
British Columbia. Today, the basaltic lava deposits are a draw to tourists and are part of the
Nisga'a Memorial Lava Beds Provincial Park.
The
Garibaldi Volcanic Belt in southwestern British Columbia, is the northern extension of the
Cascade Volcanic Arc in the
United States (which includes
Mount Baker and
Mount St. Helens) and contains the most explosive young volcanoes in Canada.
[17] It formed as a result of
subduction of the
Juan de Fuca Plate (a remnant of the much larger
Farallon Plate) under the
North American Plate along the
Cascadia subduction zone.
[17] The Garibaldi Volcanic Belt includes the
Bridge River Cones,
Mount Cayley,
Mount Fee,
Mount Garibaldi,
Mount Price,
Mount Meager, the Squamish Volcanic Field and much more smaller volcanoes. The eruption styles in the belt range from
effusive to
explosive, with compositions from
basalt to
rhyolite. Morphologically, centers include
calderas,
cinder cones,
stratovolcanoes and small isolated
lava
masses. Due to repeated continental and alpine glaciations, many of the
volcanic deposits in the belt reflect complex interactions between
magma
composition, topography, and changing ice configurations. The most
recent major catastrophic eruption in the Garibaldi Volcanic Belt was
the
2350 BP eruption of Mount Meager as well as Canada. It was similar the
1980 eruption of Mount St. Helens,
[17] sending an
ash column approximately 20 km high into the
stratosphere.
[18]
The
Chilcotin Group is a north-south range of
volcanoes in southern
British Columbia running parallel to the
Garibaldi Volcanic Belt. The majority of the eruptions in this belt happened either 6–10 million years ago (
Miocene) or 2–3 million years ago (
Pliocene), although there have been some slightly more recent eruptions (in the
Pleistocene).
[19] It is thought to have formed as a result of
back-arc extension behind the
Cascadia subduction zone.
[19] Volcanoes in this belt include
Mount Noel, the
Clisbako Caldera Complex,
Lightning Peak,
Black Dome Mountain and many lava flows.
The
Anahim Volcanic Belt is a line of volcanoes stretching from just north of
Vancouver Island to near
Quesnel,
British Columbia,
Canada. These volcanoes were formed 8-1 million years ago and the
Nazko Cone which last erupted only 7,200 years ago.
[20]
The volcanoes generally get younger as one moves from the coast to the
interior. These volcanoes are thought to have formed as a result of the
North American Plate sliding westward over a small
hotspot, called the
Anahim hotspot.
[20] The hotspot is considered similar to the one feeding the
Hawaiian Islands.
[20] The belt is defined by three large
shield volcanoes (
Rainbow,
Ilgachuz and the
Itcha Ranges) and 37
Quaternary basalt centers.
Eruptions of
basaltic to
rhyolitic volcanoes and
hypabyssal rocks of the
Alert Bay Volcanic Belt in northern
Vancouver Island are probably linked with the subducted margin flanked by the
Explorer and
Juan de Fuca plates at the
Cascadia subduction zone. It appears to have been active during the
Pliocene and
Pleistocene time. However, no
Holocene eruptions are known, and volcanic activity in the belt has likely ceased.
Russia
Avachinsky, an active volcano on the Kamchatka Peninsula.
The
Kamchatka Peninsula in the
Russian Far East is one of the most various and active volcanic areas in the world,
[21] with an area of 472,300 km². It lies between the
Pacific Ocean to the east and the
Okhotsk Sea to the west. Immediately offshore along the Pacific coast of the peninsula runs the 10,500 meter deep
Kuril-Kamchatka Trench. This is where rapid
subduction of the
Pacific Plate fuels the intense volcanism. Almost all types of volcanic activity are present, from
stratovolcanoes and
shield volcanoes to Hawaiian-style fissure eruptions.
[21]
There are over 30 active volcanoes and hundreds of
dormant and
extinct volcanoes in two major
volcanic belts. The most recent activity takes place in the eastern belt,
[21] starting in the north at the
Shiveluch volcanic complex, which lies at the junction of the
Aleutian and Kamchatka
volcanic arcs. Just to the south is the famous
Klyuchi volcanic group, comprising the twin
volcanic cones of
Kliuchevskoi and
Kamen, the huge volcanic complexes of
Tolbachik and
Ushkovsky,
and a number of other large stratovolcanoes. The only active volcano in
the central belt is found west of here, the huge remote
Ichinsky. Farther south, the eastern belt continues to the southern slope of Kamchatka, topped by loads of
stratovolcanoes.
Japan
Ten percent of the world's active
volcanoes are found in Japan, which lies in a zone of extreme crustal instability. They are formed by
subduction of the
Pacific Plate and the
Philippine Sea Plate. As many as 1,500
earthquakes are recorded yearly, and magnitudes of four to six on the
Richter scale
are not uncommon. Minor tremors occur almost daily in one part of the
country or another, causing slight shaking of buildings. Major
earthquakes occur infrequently; the most famous in the twentieth century
were: the
Great Kantō earthquake of 1923, in which 130,000 people died; and the
Great Hanshin earthquake of 17 January 1995, in which 6,434 people died. On March 11, 2011
a magnitude 8.9 Earthquake hit Japan, the country's biggest ever and the fifth largest on record, according to US Geological Survey data.
[22] Undersea earthquakes also expose the Japanese coastline to danger from
tsunamis.
Mount Bandai, one of Japan's most noted volcanoes, rises above the north shore of
Lake Inawashiro. Mount Bandai is formed of several overlapping
stratovolcanoes, the largest of which is O-Bandai forming a
complex volcano. O-Bandai volcano was constructed within a horseshoe-shaped
caldera that formed about 40,000 years when an earlier volcano collapsed, forming the
Okinajima debris avalanche, which traveled to the southwest and was accompanied by a
plinian eruption. Four major
phreatic eruptions
have occurred during the past 5,000 years, two of them in historical
time, in 806 and 1888. Seen from the south, Bandai presents a conical
profile, but much of the north side of the volcano is missing as a
result of the collapse of Ko-Bandai volcano during the 1888 eruption, in
which a debris avalanche buried several villages and formed several
large lakes.
Nearly a century ago, the north flank of Mount Bandai collapsed during an eruption quite similar to the May 18,
1980 eruption of Mount St. Helens.
After a week of seismic activity, a large earthquake on July 15, 1888,
was followed by a tremendous noise and a large explosion. Eyewitnesses
heard about 15 to 20 additional explosions and observed that the last
one was projected almost horizontally to the north.
Mount Fuji
is Japan's highest and most noted volcano. The modern postglacial
stratovolcano is constructed above a group of overlapping volcanoes,
remnants of which form irregularities on Fuji's profile. Growth of the
younger Mount Fuji began with a period of voluminous lava flows from
11,000 to 8,000 years ago, accounting for four-fifths of the volume of
the younger Mount Fuji. Minor
explosive eruptions dominated activity from 8,000 to 4,500 years ago, with another period of major
lava
flows occurring from 4,500 to 3,000 years ago. Subsequently,
intermittent major explosive eruptions occurred, with subordinate lava
flows and small
pyroclastic flows. Summit eruptions dominated from 3,000 to 2,000 years ago, after which flank vents were active. The extensive
basaltic lava flows from the summit and some of the more than 100 flank cones and vents blocked drainages against the
Tertiary Misaka Mountains on the north side of the volcano, forming the
Fuji Five Lakes. The last eruption of this dominantly basaltic volcano in 1707 ejected
andesitic pumice and formed a large new
crater on the east flank.
Scientists are saying that there may be some minor volcanic activity in the next few years.
Philippines
The 1991 eruption of
Mount Pinatubo
is the world's second largest terrestrial eruption of the 20th century.
Successful predictions of the onset of the climactic eruption led to
the evacuation of tens of thousands of people from the surrounding
areas, saving many lives, but as the surrounding areas were severely
damaged by
pyroclastic flows, ash deposits, and later,
lahars caused by rainwater remobilising earlier volcanic deposits, thousands of houses were destroyed.
Mayon Volcano overlooks a pastoral scene approximately five months before the volcano's violent eruption in September 1984.
Mayon Volcano
is the Philippines' most active volcano. The volcano has steep upper
slopes that average 35–40 degrees and is capped by a small summit
crater. The historical eruptions of this
basaltic-
andesitic volcano dates back to 1616 and ranges from
Strombolian to basaltic
Plinian eruptions. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks.
Pyroclastic flows and
mudflows
have commonly swept down many of the approximately 40 ravines that
radiate from the summit and have often devastated populated lowland
areas.
Taal Volcano
has had 33 recorded eruptions since 1572. A devastating eruption
occurred in 1911, which claimed more than a thousand lives. The deposits
of that eruption consisted of a yellowish, fairly decomposed
(non-juvenile) tephra with a high sulfur content. The most recent period
of activity lasted from 1965 to 1977, and was characterized by the
interaction of magma with the lake water, which produced violent
phreatic explosions.
Although the volcano has been dormant since 1977, it has shown signs of
unrest since 1991, with strong seismic activity and ground fracturing
events, as well as the formation of small mud geysers on parts of the
island.
Canlaon
is the most active volcano in central Philippines and has erupted 25
times since 1866. Eruptions are typically phreatic explosions of
small-to-moderate size that produce minor ashfalls near the volcano. On
August 10, 1996, Kanlaon erupted without warning, killing British
student Julian Green and Filipinos Noel Tragico and Neil Perez, who were
among 24 mountainclimbers who were trapped near the summit.
Indonesia
Major volcanoes in Indonesia
The volcanoes in
Indonesia are among the most active of the Pacific Ring of Fire. They are formed due to
subduction zones of three main active tectonic plates namely the
Eurasian Plate,
Pacific Plate, and the
Indo-Australian Plate.
[23] Some of the volcanoes are notable for their eruptions, for instance,
Krakatau for its global effects in 1883,
Lake Toba for its
supervolcanic eruption estimated to have occurred 74,000
BP which was responsible for six years of
volcanic winter, and
Mount Tambora
for the most violent eruption in recorded history in 1815. The eruption
of Mount Tambora in 1815 caused wide spread harvest failures in
Northern Europe, the Northeastern United States, and eastern Canada in
1816, which was known as the
Year Without a Summer.
The most active volcanoes are
Kelud and
Mount Merapi on
Java
island which have been responsible for thousands of deaths in the
region. Since AD 1000, Kelud has erupted more than 30 times, of which
the largest eruption was at scale 5 on the
Volcanic Explosivity Index, while Merapi has erupted more than 80 times. The
International Association of Volcanology and Chemistry of the Earth's Interior has named Merapi as a
Decade Volcano since 1995 because of its high volcanic activity.
New Zealand
Major volcanoes of New Zealand
New Zealand contains the world's strongest concentration of youthful
rhyolitic volcanoes, and voluminous sheets blanket much of the
North Island. The earliest historically-dated eruption was at
Whakaari/White Island in 1826,
[24] followed in 1886, by the country's largest historical eruption at
Mount Tarawera. Much of the region north of New Zealand's North Island is made up of
seamounts and small
islands, including 16
submarine volcanoes. In the last 1.6 million years, most of New Zealand's volcanism is from the
Taupo Volcanic Zone.
Mount Ruapehu at the southern end of the
Taupo Volcanic Zone, is one of the most active volcanoes.
[25] It began erupting at least 250,000 years ago. In recorded history, major eruptions have been about 50 years apart,
[25]
in 1895, 1945 and 1995–1996. Minor eruptions are frequent, with at
least 60 since 1945. Some of the minor eruptions in the 1970s generated
small
ash falls and
lahars (mudflows) that damaged skifields.
[26] Between major eruptions, a warm
acidic
crater lake forms, fed by melting snow. Major eruptions may completely
expel the lake water. Where a major eruption has deposited a
tephra
dam across the lake's outlet, the dam may collapse after the lake has
refilled and risen above the level of its normal outlet, the outrush of
water causing a large lahar. The most notable lahar caused the
Tangiwai disaster
in December 1953, when 151 people aboard a Wellington to Auckland
express train were killed after the lahar destroyed the Tangiwai rail
bridge just moments before the train was due. In 2000, the
ERLAWS system was installed on the mountain to detect such a collapse and alert the relevant authorities.
The
Auckland volcanic field on the North Island of New Zealand, has produced a diverse array of explosive craters, scoria cones, and lava flows. Currently
dormant, the field is likely to erupt again with the next "hundreds to thousands of years", a very short timeframe in geologic terms.
[27] The field contains at least 40 volcanoes, most recently active about 600 years ago at
Rangitoto Island, erupting 2.3 cubic kilometers of lava.
Antarctica
The Pacific Ring of Fire is completed in the south by the continent of
Antarctica,
[28]
which includes many large volcanoes. The makeup and structure of the
volcanoes in Antarctica change largely from the other places around the
ring. In contrast, the
Antarctic Plate is almost completely surrounded by extensional zones, with several
mid-ocean ridges which encircle it, and there is only a small subduction zone at the tip of the
Antarctic Peninsula, reaching eastward to the remote
South Sandwich Islands.
[28] The most well known volcano in Antarctica is
Mount Erebus, which is also the world's southernmost active volcano.
[28] In many respects the geology of the
Antarctic Peninsula is an extension of the
Andes, hence the name sometimes used by geologists: "Antarctandes". At the opposite side of the continent, the volcanoes of
Victoria Land may be seen as the 'other end' of the Antarctandes, thus completing the Pacific Ring of Fire and continuing up through the
Balleny Islands to
New Zealand.
The volcanoes of the
Victoria Land area are the most well known in Antarctica,
[28] most likely because they are the most accessible. Much of Victoria Land is mountainous, developing the eastern section of the
Transantarctic Mountains, and there are several scattered volcanoes including
Mount Overlord and
Mount Melbourne in the northern part.
[28] Farther south are two more well-known volcanoes,
Mount Discovery and
Mount Morning, which are on the coast across from
Mount Erebus and
Mount Terror on
Ross Island. The volcanism in this area is caused by
rifting along a number of
rift zones increasing mainly north-south similar to the coast.
[28]
Marie Byrd Land contains the largest volcanic region in Antarctica, covering a length of almost 600 miles (970 km) along the Pacific coast.
[28] The volcanism is the result of rifting along the vast
West Antarctic Rift, which extends from the base of the
Antarctic Peninsula to the surrounding area of
Ross Island, and the volcanoes are found along the northern edge of the rift.
[28] Protruding up through the ice are a large number of major
shield volcanoes, including
Mount Sidley, which is the highest volcano in Antarctica.
[28] Although a number of the volcanoes are relatively young and are potentially active (
Mount Berlin,
Mount Takahe,
Mount Waesche, and
Mount Siple), others such as
Mount Andrus and
Mount Hampton are over 10 million years old, yet maintain uneroded constructional forms.
[28]
The desert-like surroundings of the Antarctic interior, along with a
very thick and stable ice sheet which encloses and protects the bases of
the volcanoes, which decreases the speed of
erosion by an issue of perhaps a thousand relative to volcanoes in moist temperate or tropical climates.
Postingan
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