Yellowstone (volcano) / Yellowstone national park

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The Yellowstone is a supervolcano under the national park of the same name in the US Federal State Wyoming.

Volcanism

The Yellowstone volcano is to a stationary point under the earth's crust (similar as under Iceland or Hawaii), at which by heat liquefied rock (magma) over a geological "Hot Spot", from the Earth's mantle ascends and is particularly closely under the earth's surface. The magma ascending by the Hot Spot with the movement toward earth's surface by the hard rock formations of the Rocky Mountains one stops. In this way a constantly growing underground chamber develops. Under the enormous pressure of the magma masses accumulating there forms gas, whose pressure raises and finally to tears in the leads the rock lying over it. By these weak points in the earth's crust those escapes from magma like an explosion, whereby the roof of the magma chamber collapses and a Caldera stays. Pulverized, dust, ash and gases will become into the atmosphere hurled the rock formations lying over it and distribute themselves approximately around the globe.

Up to 2.000 usually weak earthquakes to the volcanism of the region are due annually.

Earlier outbreaks

As a result of the continental plates shifting over it readable traces of the volcanic activity arise over the millions of years. In the case of the Yellowstone this is a chain of Calderen on the North American continent. Its magma chamber lying in approx. 8 km depth is approximately 60 km long, 40 km broad and 10 km powerfully and warms up underground water occurrences, which step partly than Geysire like the old Faithful, to the surface. Geological investigations showed that the Yellowstone is active for 17 million years. The three last larger outbreaks took place before 2.1 million (Huckleberry Ridge outbreak), 1.3 million (Mesa case outbreak) and 0.64 million years (lava Creek outbreak). It is therefore assumed that about all 700,000 - 900,000 years an outbreak of the VEI strength 7 or 8 takes place. However this estimation is uncertain due to the few outbreaks. Between them there is smaller last eruptions devastated the landscape in the periphery of 250 km and colluded world-wide the sky for approximately three years. In Europe the average temperature sank by the lower sun exposure noticeably. In the Yellowstone area the last outbreaks left an overlapping entire Caldera of 80 km length and 55 km broad, whereby alone the Caldera of the last outbreak is broad approximately 40 km long and 25 km and approx. a quarter of the entire national park constitutes. The last outbreak hurled approximately 1000 km material such as ash and stones into the atmosphere. The welded together tuff and tufa formation (Ignimbrit), which thereby developed, lava Creek Tuff one calls. Today Rhyolit and basalt stones in the Yellowstone area cover approximately 340 km

First of the three was substantially stronger mentioned outbreaks approximately 2.1 million years ago. A Caldera of approx. 80 times 50 kilometers developed. Approximately 2500 km material were ejected. The second eruption approximately 1.3 million years ago was the smallest of the three; only 280 km material were ejected.

Next outbreak

Due to the past outbreak cycle and geological changes, for example the raising of the Calderastruktur in the last decades, an outbreak is expected in geologically close time, thus within next thousands of years.

According to the sample of the seismic activities changes current observations (conditions March 2006) since 1995. US the Geological Survey (USGS) reports that itself the northern Kraterrand main header, while the basis lowered itself. These movements moving in opposite directions constantly increased, were stopped in the year 2003 however again approximately.

These movements are probably caused by melted basalt, which flows in the underground lava courses. Into the 1990er years these were strengthened probably by the fact that a lava thrust flowed out of a reservoir in the upper Earth's mantle into the Yellowstone Vulkansystem. Since apparent only little lava flowed off again, the pressure increased, whereby new rock gaps developed, which created again a better connection to the more deeply lying lava reservoir. The movements led to increased geothermal activities in this area.

Such phases "thermal unrest "took place according to the scientists of the USGS already repeated, so far without consequences.

If it comes to an outbreak, typically several magma break-throughs develop at the periphery of the Caldera, while the center of the Caldera sinks. Will large quantities of lava and dust into the highest layers of the atmosphere hurled and a large part of North America will be covered by an ash layer. The pressure wave of the explosion would orbit, similarly as with the explosion of the Krakatau, the earth several times. As effect for the earth a volcanic winter is expected of several years duration. The Yellowstone volcano is therefore the largest at present well-known potential trip of a natural catastrophe.