Krakatoa VS. Mt. St. Helens VS. Yellowstone Volcano ( soon )

[MORTARDUDE]

There are estimates of 16,000,000+ dead ( not injured ) in the USA alone...

>>>>>>>>>>>>>>>>>


http://www.wyomingtalesandtrails.com/ystoneggate.html

In Yellowstone there was older volcanic activity 55 to 40 million years ago. During that time the Absaroka and Washburn Ranges were formed. However, the formation of the most prominent features of present-day Yellowstone began two million years ago. As the area drifted over the hot spot, an explosive rhyolite lava accumlated beneath what is now the Park. From cracks in the overlying rocks, lava oozed, releasing pressure on the remaining molten rock, permitting it to explosively expand. The force of the explosion was many times that of the eruption of St. Helens or that of Krakatoa in 1883. The Krakatoa explosion could be heard 3,000 miles away and formed a dust cloud 50 miles high. The size of the Yellowstone Hot Spot explosions may be illustrated by the fact that an earlier eruption in Idaho 10 million years ago, buried alive in volcanic dust, camels, rhinoceros, and deer in northeast Nebraska almost a 1000 miles away. Most traces of the explosion from 2 million years ago have disappeared, destroyed by another violent explosion 1,200,000 years ago and one only 600,000 years ago. The more recent eruption formed a caldera over 30 miles wide, much of which now forms the Lake Yellowstone basin.



http://www.d.umn.edu/~rmorton/ronsho.../calderas.html
Caldera Volcanoes
(Also called Bathtubs Volcanoes)
It was Charles Darwin who said "Nothing, not even the wind that blows, is so unstable as the crust of this earth." and that brings us to Bathtub Volcanoes.

These volcanoes are the deadliest, stickiest, nasttiest, gassiest of the entire lot.

Their eruptions can be earth shaking, cataclysmic- they can have the power of many nuclear explosions. They may bring famine, pestilence, tsunamis, plaques, great pyroclastic flows, darkness for many days or months, global climatic change, and, possibly, very pretty sunsets.

Caldera volcanoes are ones where the diameter of the circular to oval crater exceeds 1 mile. These form when so much lava is erupted (blown out) so rapidly it partially empties the underlying magma chamber. When this happens the summit of the volcanic structure collapses into the emptied magma chamber. Typically the erupted material occurs as airfall or pyroclastic flows.

There have been no recent eruptions from caldera volcanoes- Valley of Ten Thousand Smokes was the last and before it there was Krakatoa (1886) and Tambora (1815)- which caused the year without a summer. Three most famous examples in North America are Yellowstone,Crater Lake, and Long Valley.

Overall at least 138 caldera volcanos, whose crater exceeds 5 miles in diameter, are known. Unlike Crater Lake , many of these have calderas so large and irregular they remained undetected until high-quality aerial or satellite images became available. One of these, LaGarita, located in the San Jauan mountains of southern Colorado is some 20 miles wide and 60 miles long, Yellowstone, with a caldera of 24 by 40 miles is another example. Both these calderas were formed due to the large scale evacuation of a near surface magma chamber (think of the amount of material that has to be blown out to create a hole many miles in diameter and 1,000's of feet deep),and the collapse of the overlying rocks into it.

The eruptions from these caldera volcanoes are largely explosive leading to extensive air fall and pyroclastic flow deposits.

Where they occur:

Hotspots- Yellowstone

Island Arcs- Krakatoa, Tambora, Toba, Taupau

Continental Mountains- Crater Lake,

Precambrian Example- Sturgeon Lake- Ontario- a large caldera volcano some 2.7 billion years old

Two kinds of Caldera Volcanoes:

Stratovolcanoes that turn into calderas due to cataclysmic eruptions- Crater lake, Tambora, Krakatoa.
Negative volcanoes- no sign of a volcanic ediface- usually just a large lake or a depression with lots of hot springs- Taupo, Long Valley, Yellowstone, Toba, Sturgeon Lake.

http://www.armageddononline.org/




http://www.arkansas.us.mensa.org/arc.../krakatoa.html



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Krakatoa


The Explosion Heard Round the World table of contents

By Duke Heath



Later in this issue we will look at a couple of the greatest volcanos in history. One of them nearly wiped out the human race and the other devastated the entire United States and may do so again very soon. To understand the magnitude of the explosions of those two super volcanos, I want to focus on the largest explosion ever heard in recorded history. The magnitude of the explosion we are about to examine is a fraction of the two super volcanos we will look at later in this issue.

On August 26, 18$3 the Indonesian island of Krakatau exploded with devastating fury. The eruption was one of the most catastrophic natural disasters in modern times. The effects of this explosion were experienced around the world. Ash from the eruption fell as far away as New York. Volcanic dust filled the upper levels of the atmosphere and changed the Earth's weather for several years.

Several tidal waves, some much more than a hundred feet high, radiated out from the colossal event throughout the Indian Ocean, across the Pacific Ocean and even reaching as far away as the English Channel. The waves were so powerful that they hurled coral rocks onshore weighing more than 600 tons each. 36,000 people were killed as these giant waves destroyed 165 coastal villages.

Krakatoa had been silent for about 200 years when seismic activity began increasing. On May 20, the volcano became active. The initial explosive eruptions of Krakatoa could be heard 100 miles away. Steam and ash could be seen rising several miles into the sky.

By August 11, 1883, three vents were actively erupting. Eleven other vents were ejecting smaller quantities of steam, ash and dust. By the August 26, explosions were occurring every ten minutes. Sailors on ships a hundred miles away reported a black cloud of smoke rising above the volcano. The volcanos central vent was blacked by a solid plug of lava and the pressure underneath it had begun increasing rapidly.


Through the 4,157 mile long Nile was all-important to Egypt, Europeans were the first to trace the Nile to Its source. In 1857, John Speke reached a great equatorial lake that he named Lake Victoria, for his Queen. Many rivers flowed into the lake, but the Nile issued from it.

At this time, Krakatoa's crater was about 1000 meters in diameter with a depth of about SO meters. (Compare this with the size of Yellowstone's caldera at 53 miles by 28 miles.) As the walls of the volcano began to collapse, sea water poured into the volcano's caldera. The superheated steam created tremendous pressure. The resultant explosion blew the island apart. This was the most severe volcanic explosion in modem times. A cloud of ash rose 17 miles into the atmosphere.

The explosion of Krakatoa was equivalent to a 200 megaton nuclear bomb. By contrast, the Hiroshima bomb was less than 20 kilotons. The eruption has been assigned a Volcanic Explosive index of 6. This rates as colossal. The volume of earth displaced by the explosion was estimated to be between 14 and 100 cubic kilometers.

The amount of material ejected into the upper atmosphere has been estimated to be about l I cubic miles. This dust cloud completely covered the area. The skies were dark 260 miles away. The darkness lasted more than three days.

Pumice from the eruption formed large thick floating rafts which crossed the Indian Ocean and remained floating for two years following the eruption. Ash fell on ships thousands of miles away.

The sound of the explosion was heard far thousands of miles, covering almost a third of the earth's surface. The echoes of the explosion continued reverberating for several hours. Atmospheric pressure shock waves circled the earth at least seven times and were recorded by every barograph throughout the world over the next five days.

The ash which was ejected into the atmosphere caused major climatic changes world wide. The average temperature of the planet fell 1.2 degrees and did not return to normal for five years.

Three months after the eruption the ash caused such vivid red sunset afterglows that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration. Unusual sunsets continued for 3 years.



http://www.calstatela.edu/faculty/acolvil/volcanos.html



Volcanos with large amounts of air fall and pyroclastic flows.
Yellowstone Natl. Park
2.2 million years
2500 cubic kilometers
identifiable volume*

Yellowstone Natl. Park
1.2 million years
280 cubic kilometers

Yellowstone Natl. Park
0.6 million years
1000 cubic kilometers

Tambora, Indonesia**
1815
150 cubic kilometers
1816 _"year without a summer" = crop failures
Mazama, Oregon
6600 years
75 cubic kilometers
Now known as Crater Lake.

Krakatoa, (near Java)
1883
>18 cubic kilometers

Katmai, Alaska
1912
7 cubic kilometers

St. Helens, Washington
1980
1 to 2 cubic kilometers

Long Valley Caldera, CA 700,000 years 520 cubic kilometers Produced the Bishop tuff

[sn-e3]

Larrry I really appreacate the georophy lesson and the power released by vulcanoes but If and when it happens. I'll look on the bright side, that will be hunting and fishng season is open and there will be no limits at least I'll die HAPPY.

[Boats]

So much for the meter impact we could self destruct at any time should old mother earth decide to blow her top. Not much one can do about that.

Though the data was impressive and I learned something.
Thanks