Sunday, July 12, 2009

VOLCANIC ERUPTIONS

Somewhere on earth, a volcanic eruption is either happening or about to happen. About 1,500 of them have erupted at different times within the last 10,000 years and, because we never know when one becomes extinct, it is possible that any one of the 1,500 could spring into life again.

One of the easiest volcanic eruptions to study can be found in Hawaii. Mount Kilauea on the Island of Hawaii, often referred to as the Big Island, is an intra-plate volcano, that is to say it is erupting from inside a tectonic plate rather than at the junction of two plates. It is erupting almost daily at the present time and at such a low level of violence that its activity can be easily observed. Molten magma just oozes out. The entire island group that constitutes the state of Hawaii is formed from volcanic action and the Big Island, the island of Hawaii, is the principal actor at the present time. Other islands of the state were active in the past and this condition is a reminder of another feature of Hawaii—it is a hot spot. There are more than thirty of these hot spots around the world.. What is a hot spot? They are places deep in the earth below the level of mountains and ocean crust from which magma is escaping to the surface. In sharp contrast to everything we see on the surface of the earth these hot spots do not move with respect to the surface of the earth. Instead the tectonic plates pass over them as they move.

The huge volume of molten rock that reaches the surface in the island of Hawaii over time from the hot spot is evident in the thousands of feet to which a volcano such as Kilauea has risen above sea level and its height is achieved after it has already risen many thousands of feet from the ocean floor up to sea level. Over a period of a few million years, Kilauea will move way from the hot spot as the Pacific Tectonic Plate on which it sits continues its westward movement. A new mountain will take shape over the hot spot and Mount Kilauea will gradually cool down to become inactive like the rest of the state of Hawaii. The long history of this process, over a period of more than seventy million years, can be observed today in the islands above and below sea level that stretch from Kilauea to the other islands of the state of Hawaii, and then across the Pacific all the way to the Kamchatka Peninsula of Russia. These islands form the Hawaiian-Emperor Chain and identification of their age, that is to say, the lapse of time since they were magma rising from the hot spot, tells the story of the movement of the Pacific Tectonic Plate over time.

Volcano Structure

The huge volume of molten rock that reaches the surface in the island of Hawaii over time from the hot spot is evident in the thousands of feet to which a volcano such as Kilauea has risen above sea level and its height is achieved after it has already risen many thousands of feet from the ocean floor up to sea level. Over a period of a few million years, Kilauea will move way from the hot spot as the Pacific Tectonic Plate on which it sits continues its westward movement. A new mountain will take shape over the hot spot and Mount Kilauea will gradually cool down to become inactive like the rest of the state of Hawaii. The long history of this process, over a period of more than seventy million years, can be observed today in the islands above and below sea level that stretch from Kilauea to the other islands of the state of Hawaii, and then across the Pacific all the way to the Kamchatka Peninsula of Russia. These islands form the Hawaiian-Emperor Chain and identification of their age, that is to say, the lapse of time since they were magma rising from the hot spot, tells the story of the movement of the Pacific Tectonic Plate over time.

The USGS scientists, particularly horrified by the things that happen to people at volcanic sites, decided to do something to alert people to the dangers and to inform them about how to avoid an imminent event. They devised a three-part action plan.

  • First, they produced a video depicting the typical phases of volcanic eruptions and what happens to people, buildings, and environment when they erupt. It was quite a scary video, deliberately so, not suitable for younger people.
  • Second, they selected fifteen volcano sites from around the world to study intensely and to examine along with the various local authorities in order to have the details of a collection of representative case studies.
  • The third element was instrumental usage for predicting when a volcano would blow given that the advance signals were evident. In 1991 the video was rushed to the Philippines when Mount Pinatubo was threatening to erupt.

The day after it was shown on television, about 50,000 chose to evacuate voluntarily. A few days later the volcano erupted. Tens of thousands of lives had been saved.

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