posted on Oct, 6 2004 @ 03:51 PM
Then second favorite thing.
Propably biggest eruption to millions of years was Toba's eruption:
There is substantial evidence to show that within the time of the supervolcano Toba's eruption in the Indonesian Pacific, the world's
population of homo sapiens decreased from over one hundred thousand to less than two thousand, basically because global temperatures dropped five
degrees for many years. This was within the current interglacial and at its start.
The Mount Toba eruption is dated to approximately 71,000 years ago. Volcanic ash from Mount Toba can be traced north-west across India, where a
widespread terrestrial marker bed exists of primary and reworked airfall ash, in beds that are commonly 1 to 3, and occasionally 6 meters [18 feet]
Tambora, the largest known historic eruption, displaced 20 cubic kilometres of ash. Mount Toba produced 800 cubic kilometres.* It was therefore forty
times larger than the largest eruption of the last two centuries and apparently the second largest known explosive eruption over the last 450 million
*Mount St Helens produced a tiny 0.2 cubic kilometres.
Volcanic Winter, and Differentiation of Modern Humans
Mount Toba's eruption is marked by a 6 year period during which the largest amount of volcanic sulphur was deposited in the past 110,000 years. This
dramatic event was followed by 1000 years of the lowest ice core oxygen isotope ratios of the last glacial period. In other words, for 1000 years
immediately following the eruption, the earth witnessed temperatures colder than during the Last Glacial Maximum at 18-21,000 years ago.
For the volcanic aerosols to be effectively distributed around the earth, the plume from the volcanic eruptions must reach the stratosphere, a height
greater than 17 kilometres. Mount Toba's plume probably reached twice this height. Most solar energy falls at low latitudes between the Tropics of
Cancer and Capricorn, so eruptions that happen near the Equator cause much more substantial cooling due to the reflection of solar energy. Toba lies 2
degrees north of the Equator, on the Island Sumatra.
The reduction in atmospheric visibility due to volcanic ash and dust particles is relatively short-lived, about three to six months. Longer-term
global climatic cooling is caused by the highly reflective sulphuric acid haze, which stays suspended in the upper atmosphere for several years.
Ice core evidence implicates Mount Toba as the cause of coldest millennium of the late Pleistocene. It shows that this eruption injected more sulphur
that remained in the atmosphere fo a longer time [six years] than any other volcanic eruption in the last 110,000 years. This may have caused nearly
complete deforestation of southeast Asia, and at the same time to have lowered sea surface temperatures by 3 to 3.5 degrees centigrade for several
If Tambora caused the " The year without a summer" in 1816, Mount Toba could have been responsible for six years of relentless volcanic winter, thus
causing a massive deforestation, a disastrous famine for all living creatures, and a near extinction of Humankind.
Today bottom of caldera is rising again, entire Samosir island is mark of that.
Other "supervolcano" is Yellowstone, actually big part of Yellowstone's valley belongs to caldera.
The Yellowstone Plateau volcanic field developed through three volcanic cycles spanning two million years that included some of the world's
largest known eruptions. Eruption of the >2450 cu km Huckleberry Ridge Tuff about 2 million years ago created the more than 75-km-long Island Park
caldera. The second cycle concluded with the eruption of the Mesa Falls Tuff around 1.3 million years ago, forming the 16-km-wide Henrys Fork caldera
at the western end of the first caldera. Activity subsequently shifted to the present Yellowstone Plateau and culminated 640,000 years ago with the
eruption of the >1000 cu km Lava Creek Tuff and the formation of the present 45 x 85 km caldera. Resurgent doming subsequently occurred at both the NE
and SW sides of the caldera and voluminous (1000 cu km) intracaldera rhyolitic lava flows were erupted between 150,000 and 70,000 years ago.
Also Long Valley is big volcanic caldera.
Volcanic activity began in the area about 3.6 million years ago when trachybasalt and trachyandesite lava flows covered an area of about 1,500
square miles (4,000 square km). A short time later, geologically speaking, rhyodacite was erupted as flows and domes. Geologists interpreted these
more silica-rich compositions as the first eruptive products of a growing magma chamber.
The Long Valley caldera was produced by a catastrophic eruption about 730,000 years ago. The roof above the magma chamber collapsed, forcing 150 cubic
miles (600 cubic km) of rhyolitic magma to the surface in the form of Plinian ash columns and associated air falls and ash flows. The volume of ash is
comparable to similar caldera-forming eruptions at Yellowstone and far exceeds the volume of ash erupted from stratovolcanoes. For example, the large
eruption of Tambora in 1815 produced 10 cubic miles (40 cubic km) of ash.
Biggest eruption in Cascades for million years was eruption of Mount Mazama... which is currently known as Crater Lake
Aerial photo: students.washington.edu...
The cataclysmic eruption of Mount Mazama 7,700 years ago started from a single vent on the northeast side of the volcano as a towering column
of pumice and ash that reached some 30 miles (50 km) high. Winds carried the ash across much of the Pacific Northwest and parts of southern Canada.
New Zealand has also own caldera... Lake Taupo.
The 181AD Taupo eruption
This eruption took place from a vent or vents near the Horomatangi Reefs, now submerged on the eastern side of Lake Taupo. The eruption lasted between
several days and several weeks and produced a sequence of pumice deposits that blanketed the landscape east of Taupo. In total about 100km3 was
At the climax of this eruption, about 30km3 of pumice, ash and rock fragments was erupted in only a few minutes and travelled horizontally as a liquid
flow, moving at speeds estimated at between 600-900kmh. It crossed every obstacle in its path except the top of Mt Ruapehu.
it produced an eruption column 50km high -- twice as high as the 1980 Mt St Helens eruption column.
it was the most violent eruption in the world in the past 5000 years.
Taupo volcano represents a major scientific challenge in that its activity is so variable. In the last 50,000 years, it has had eruptions that vary in
volume from 0.05km3 (slightly larger than a typical Ruapehu eruption) to over 800km3.
One the most violent recent eruption was Krakatau.
After a long period of inactivity (about 200 years), Krakatoa became active again in early 1883. The first indication that something was
happening on Krakatoa was when a large earthquake struck the area. Seismic activity became stronger until May 20,1883, when the volcano abruptly came
to life. The initial explosive eruptions of Krakatoa could be heard 160 km away. Steam and ash could be seen rising 11km above the summit of the
volcano. By August 11, 1883. three vents were actively erupting. Eleven other vents were ejecting smaller quantities of steam, ash and dust.
Around 1 pm on the 26th of August 1883, the explosions became more frequent occurring on the average every 10 minutes. Sailors on a ship, 120 km away
from the island reported a black cloud of smoke rising above the volcano. At the time the rim of Krakatoa's crater was approximately 1,000 meters in
diameter and had and average depth of 50 meters. The volcano' s central vent was blocked by a plug of solid lava and underneath it pressure was
rapidly building up.
The Great Eruption
The renewed activity in May 1883 culminated in four gigantic explosions on August 26 and 27 of the same year. On the afternoon of August 26, 1883, (27
August local date) at 17: 07 Greenwich time (GMT), the first of these four violent explosions begun. A black cloud of ash was initially observed. It
rose 17 miles (27 kilometers) above Krakatoa. In the morning of the next day, on August 27, 1883, at 05:30, 06:44 and 10:02 GMT, three more violent
eruptions occurred. It was the paroxysmal eruption which occurred at 10:02 which blew away the northern two-thirds of the island. This was the most
severe violent volcanic explosion on Earth in modern times. The explosion was followed by the collapse of the unsupported volcanic chambers of
Krakatoa forming the huge underwater caldera. It was this explosion and collapse of Krakatoa that generated catastrophic tsunami waves as high as 37
meters. (120 ft.) that caused havoc and destruction in the Sunda Strait.
The 1883 eruption of Krakatoa has been assigned a Volcanic Explosivity Index or VEI of 6 which rates as "colossal". To be assigned a VEI rating of
6, a volcanic eruption must have a plume height over 25 km and a displacement volume ranging between 10 and 100 km3 (cubic kilometers). Eruptions of
this size occur only once every few hundred years on earth.
The total energy released by the four main events of the 1883 eruption was equivalent to 200 megatons of TNT. Most of this energy was released by the
third paroxysmal explosion which has been estimated to be equivalent to an explosion of 150 megatons of TNT. To understand the magnitude of the
Krakatoa explosion, it will suffice to say that the Hiroshima atomic bomb was only about 20 kilotons).
This frightening display of volcanic power would culminate in a series of at least four stupendous eruptions that began at 5:30 a.m., climaxing
in a colossal blast that literally blew Krakatau apart. The noise was heard over 4600 km away, throughout the Indian Ocean, from Rodriguez Island and
Sri Lanka in the west, to Australia in the east.
One compeling feature of the Krakatau eruption is that the pyroclastic flows appear to have travelled an incredible 40 km across the Sunda Straits,
where they remained hot enough to cause the burn-related fatalities on Sumatra. These same flows, however, were also recorded by several ships located
at greater distances. On August 27, the Louden (see above) was located ~65 km north-northeast of Krakatau when it was struck by severe winds and
tephra, and the W.H. Besse was located at ~80 km east-northeast of Krakatau when it was hit by hurricane-force winds, heavy tephra, and the strong
smell of sulfur. At these greater distances, the pyroclastic flows were at lower temperatures so that the ships and crew survived.
Even these eruptions can cause extinction of local cultures.
Like eruption of Santorini which devastated Minoan culture and might have caused legend of Atlantis.
Like so many other volcanoes this is also growing again and might eventually erupt again.
Compared to those St. Helens is small backyard campfire.
The powerful lateral blast from Mount St. Helens on May 18, 1980 swept 30 km away from the volcano, blowing down giant trees like matchsticks. The
blast, traveling at velocities up to 1100 km per hour, devastated 600 sq km over a broad area nearly 180 degrees wide north of the volcano.
I wouldn't keep eruption of supervolcano so propable but for example there are lot of Volcanoes in western US which could cause big consequencis
"locally" (500 mile radius) if volcano has good day.