The Yellowstone caldera, in the United States, is a well-known volcanic complex, and in the media associated with the superlative " supervolcano". The site is physically very active and has many interesting phenomena, both from scientific point of view, and also… tourism. The geysers are perhaps the most known, but there are also hot springs, gas emissions, and it also houses a very diverse flora and fauna. The site is protected as a nature reserve.
The caldera has witnessed colossal eruptions, the last one 640,000 years ago. Earthquakes are frequent. Their analysis revealed changes in rock density below the park, and this is interpreted as a partially melted area, so a magma chamber. The stored heat there is also the origin of geothermal activity.
It is not the purpose of this post to make a full description of the complex, and it will be done later in another article, but interesting information about the behavior of the giant was recently published, in particular the eruption dynamics.
Indeed, smaller eruptions have occurred more recently, but they are of lower intensity. Determining their probable location is complex. The presence of fractures may influence the location of future eruptions. Those seem to remain unlikely in the short term, the amount of molten magma seem low (less than 30%). Note also that the lavas are rhyolites with an explosive potential due to their generally high viscosity.
The presence of smaller-scale eruption shows that the adjective "supervolcano" should be replaced by "super-eruption" limited to some of them.
However, examination of the composition of rejected lavas indicate a rapid rise of magma from the main chamber at a depth of 10 kilometers, without intermediate storage at a shallower depth. This indicates that, from the moment the eruption process is triggered, the time of apparition of the lava at the surface may be small and it could be more difficult to detect this process.
This makes monitoring even more important.
Sources:
http://www.geosociety.org/gsatoday/archive/22/9/article/i1052-5173-22-9-4.htm
USGS (various pages)
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