The Pacific Ring of Fire is an area of frequent
earthquakes and
volcanic eruptions encircling the basin of the
Pacific Ocean. In a 40,000 km 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. It is sometimes called the circum-Pacific belt or the circum-Pacific seismic belt.
Ninety percent of the world's earthquakes and 80% 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.
[1][2]The Ring of Fire is a direct result and consequence of
plate tectonics and the movement and collisions of crustal plates.
[3] 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. 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.
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.
[4][5] The active
Queen Charlotte Fault on the west coast of the
Queen Charlotte Islands,
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.
[6]The
December 2004 earthquake just off the coast of Sumatra was actually a part of the
Alpide belt.
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 (1,094 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 up 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) downdip from the deformation front. Further downdip, 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 km3 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.
A
volcanic ash column rose high into the
atmosphere and deposited ash in 11 U.S. states. At the same time, snow, ice, and several entire
glaciers on the mountain melted, forming a series of large
lahars (volcanic
mudslides) that reached as far as the
Columbia River. Less severe outbursts continued into the next day only to be followed by other large but not as destructive eruptions later in 1980. By the time the ash settled, 57 people (including innkeeper
Harry Truman and geologist
David A. Johnston) and thousands of animals were dead, hundreds of square miles reduced to wasteland, over a billion
U.S. dollars in damage had occurred ($2.74 billion in 2007 dollars
[7]), and the face of Mount St. Helens was scarred with a huge crater on its north side. At the time of the eruption, the summit of Mount St. Helens was owned by the
Burlington Northern Railroad, but afterward the land passed to the
United States Forestry Service. The area was later preserved, as it was, in the
Mount St. Helens National Volcanic Monument.
Native Americans have inhabited the area for thousands of years and developed their own
myths and
legends concerning the Cascade volcanoes. According to some of these tales, Mounts
Baker,
Jefferson,
Shasta were used as refuge from a great
flood. Other stories, such as the
Bridge of the Gods tale, had various High Cascades such as
Hood and
Adams, act as god-like chiefs who made
war by throwing fire and stone at each other.
St. Helens with its pre-1980 graceful appearance, was regaled as a beautiful maiden for whom Hood and Adams feuded. Among the many stories concerning Mount Baker, one tells that the volcano was formerly married to Mount Rainier and lived in that vicinity. Then, because of a marital dispute, she picked herself up and marched north to her present position. Native tribes also developed their own names for the High Cascades and many of the smaller peaks, the most well-known to non-natives being Tahoma, the
Lushootseed name for
Mount Rainier.
Legends associated with the great volcanoes are many, as well as with other peaks and geographical features of the arc, including its many hot springs and waterfalls and rock towers and other formations. Stories of Tahoma - today
Mount Rainier and the namesake of
Tacoma, Washington - allude to great, hidden grottos with sleeping giants, apparitions and other marvels in the volcanoes of
Washington, and
Mount Shasta in California has long been well-known for its associations with everything from
Lemurians to aliens to elves and, as everywhere in the arc,
Sasquatch or
Bigfoot.
In the spring of 1792 British navigator
George Vancouver entered
Puget Sound and started to give
English names to the high mountains he saw.
Mount Baker was named for Vancouver's third lieutenant, the graceful
Mount St. Helens for a famous diplomat,
Mount Hood was named in honor of
Samuel Hood, 1st Viscount Hood (an
admiral of the
Royal Navy) and the tallest Cascade,
Mount Rainier, is the namesake of Admiral
Peter Rainier. Vancouver's expedition did not, however, name the arc these peaks belonged to. As marine trade in the
Strait of Georgia and
Puget Sound proceeded in the 1790s and beyond, the summits of
Rainier and
Baker became familiar to captains and crews (mostly British and American over all others, but not exclusively).
With the exception of the 1915 eruption of remote
Lassen Peak in
Northern California, the arc was quiet for more than a century. Then, on
May 18,
1980, the dramatic eruption of little-known
Mount St. Helens shattered the quiet and brought the world's attention to the arc.
Geologists were also concerned that the St. Helens eruption was a sign that long-dormant Cascade volcanoes might become active once more, as in the period from 1800 to 1857 when a total of eight erupted. None have erupted since St. Helens, but precautions are being taken nevertheless, such as the Mount Rainier Volcano
Lahar Warning System in
Pierce County, Washington.
CANADA:
Although little-known to the general public,
British Columbia and the
Yukon Territory is home to a vast region of volcanoes and volcanic activity in the Pacific Ring of Fire.
[9] 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.
[10] 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,
Lava Fork,
Mount Edziza,
Hoodoo Mountain,
Crow Lagoon and
Nazko Cone.
[11] 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,
[9] much larger than the minor
stratovolcanoes found in the Canadian portion of the
Cascade Volcanic Arc.
[9] 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 wth
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
Lava Fork produced some of Canada's youngest lava flows, that are about 150 years old.
Canada's worst known geophyical 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 contain 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.
[12] 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.
[12] 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,
[12] sending an
ash column approximately 20 km high into the
stratosphere.
[13]The
Chilcotin Plateau Basalts are 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).
[14] It is thought to have formed as a result of
back-arc extension behind the
Cascadia subduction zone.
[14] 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.
[15] The volcanoes generally get younger as you go 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.
[15] The hotspot is considered similar to the one feeding the
Hawaiian Islands[15] 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.
INDONESIA:
The volcanoes in
Indonesia are among the most active of the Pacific Ring of Fire. They are formed due to
subduction zones between the
Eurasian Plate and the
Indo-Australian Plate. 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 most active volcanoes are
Kelut and
Merapi on
Java island which have been responsible for thousands of deaths in the region. Since AD 1000, Kelut 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.
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 and
Philippine plates. 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 17th January 1995, in which 6,434 people died. Undersea earthquakes also expose the Japanese coastline to danger from
tsunamis.
Mount Bandai is 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.
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.
[16] 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.
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 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.
Kanlaon 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.
KAMCHATKA PENINSULA:
The
Kamchatka Peninsula in the
Russian Far East, is one of the most various and active volcanic areas in the world,
[17] 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.
[17]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,
[17] 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.
NEW ZEALAND:
New Zealand contains the world's strongest concentration of youthful
rhyolitic volcanoes, and voluminous sheets blanket much of
North Island. The earliest historically-dated eruption was at
Whakaari/White Island in 1826.
[18] 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.
[19] It began erupting at least 250,000 years ago. In recorded history, major eruptions have been about 50 years apart,
[19] 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.
[20] 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. 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.
[21] The field contains at least 40 volcanoes, most recently active about 600 years ago at
Rangitoto, erupting 2.3 cubic kilometers of lava.
CHILE:
Volcanoes of Chile are related to
subduction of the
Nazca Plate to the east.
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-kilometer wide
caldera formed during the late
Pleistocene, >0.9 million years ago. A 2-kilometer-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 volcano have damaged towns on its flanks.
This year Chile has experienced two volcanic eruptions, the first one from Llaima Volcano (January 1) and Chaitén Volcano (May 1).
ANTARTICA:
The southernmost end of the Pacific Ring of Fire is the continent
Antarctica,
[22] 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.
[22] The most well known volcano in Antarctica is
Mount Erebus, which is also the world's southernmost active volcano.
[22]The volcanoes of the
Victoria Land area are the most well-known in Antarctica,
[22] 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.
[22] 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.
[22]Marie Byrd Land contains the largest volcanic region in Antarctica, covering a length of almost 600 miles (960 km) along the Pacific coast.
[22] 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.
[22] Protruding up through the ice are a large number of major
shield volcanoes, including
Mount Sidley, which is the highest volcano in Antarctica.
[22] 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.
[22] 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.
n gives off an aquatic aroma and comes with sky and wave imagery on the cover.
