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23 Eruption of Mount St. Helens
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In the course of the gigantic eruption of the Mount St. Helens volcano in the year 1980, within hours and days geological formations were created which correspond very closely to others which, up to now, were thought to have been formed in a process taking thousands and millions of years. The observations of Mount St. Helens illustrate the fact that the geological formations of our earth could have been formed in a series of short catastrophic events.
Before the eruption in the year 1980, Mount St. Helens in the north-western USA was approximately 400m higher than it is today. As a result of the heat generated by the eruption, the snow in the area of the summit of the just short of 3,000m high mountain mingled with sediments and rock debris. The streams of debris and mud flowed down into the valley at speeds of up to 150 km/h and, within short time, eroded canyons up to 200m deep in the solid rock.
Regarding other canyons in America, most geologists assume that they were slowly carved out by the water of rivers during very long periods of time (slow erosion). The eruption of Mount St. Helens proves, however, that such geological formations can develop in a very short time.
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Eruption Mount St. Helens
As a result of the explosion, around a million tree trunks were hurled into the nearby Spirit Lake. New canyons and new river system and lakes were created and the Spirit Lake was raised by around 75 m in total (1).
After the eruption, the lake was covered with an immense mat of Douglas Fir, Noble Fir, Hemlock Fir, Silver Fir, Western-Red-Cedar and Alaska-Yellow-Cedar. Careful observations have shown that the trunks tend to float in an upright position with the roots downwards. In the course of time the trees sank and were deposited on the lakebed. Some of the trees embedded themselves upright on the lakebed.
If we were to find these trunks in fossilised form within rock strata, then they would appear to us to be a naturally growing forest. It would seem that a forest of Noble Firs was followed by a forest of Hemlock Firs and finally by a forest of Douglas Firs. The buried forests in the Ruhr Coal Basin can be quoted as an example from the past. At that time, many tons of cortex trees up to 12m high during the Carboniferous period were completely buried in the mud (2).
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Mount St. Helens in 1980 and 2007
The formation of peat and coal:
The waves in the Spirit Lake caused friction between the tree trunks. This had the effect that water-soaked bark pieces broke away from the trunks and gradually covered the lakebed. Thus, within a few years, a several centimetre deep peat layer was created, which consists of up to 25% tree bark. Analysis showed that this peat has a close structural relationship to coal. Perhaps in the Spirit Lake we are witnessing the first stage of the formation of coal.
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