A basic summary of Yellowstone and it's threats, page 1

I'm interested in this, and a lot of people probably are, so I feel a new informative thread about the topic would be a good idea since any other information on here is probably a bit out of date now.

The activity at Yellowstone is, like it has been for the past 70,000 years or so (time since the last eruptive activity), at background levels of seismicity. This doesn't necessarily mean nothing is happening though, only that the area is currently rather quiet and is likely to remain as it is. However no one can really say whether or not nothing is coming since no one anywhere has really accurately predicted what a volcano will do. This is mostly because the volcanologists have no perfect way of seeing what is under the volcano, the state of the magma chamber, or anything else that would likely be a good warning of activity.

As such, there are several things that volcanologists, and the public in general to a lesser extent, can look at with regard to the current state of things. These thing are Earthquake activity, Ground 'Deformation, and Hydrologic monitoring. Earthquake activity is the easiest to visualise and observe, as the world in general has a good number of stations to analyse seismic activity with, and these are linked up to the internet such that anyone with a connection can see them. The most obvious one is the main USGS one, though there are others which are more useful depending on where you want to see.

So, earthquake activity at Yellowstone. This varies a lot from month to month, for the past year from as few as 46 to as many as 263. It must be noted that these are large numbers from first glance, but are background levels. There are images of the locations of these quakes as well available on the internet. These seem to be available from Utah University, here. As can be observed from these maps, there are certain areas where a lot of earthquakes occur, and from the 1973-2001 map, there seems to be a general trend towards a shape that is similar to the shape of the previous Caldera(the green line), rotated 90o. This may be indicative of the shape of the magma chamber underneath Yellowstone, which will be of a very large volume.

Current maps of the seismic activity at Yellowstone are also available from the University of Utah here, and show the last week of activity. Currently there seems to be a swarm near the area of the 1959 Hebgen Lake earthquake. There are also live seismograms of the area around Yellowstone. These are available from here. They are not the easiest thing to get information from however as just about anything can appear on them, especially larger, distant earthquakes. As such it is best to check for the interesting looking event on another plot, and check the time it occurs at against the list of magnitude 5+ earthquakes available from the main USGS site. It must be known though, that it takes considerable time for a large event's seismic waves to reach distant seismograms.

Ground Deformation can be measured as well and gives a neat idea of where there is currently magma moving around. It is not indicative of an eruption generally, as in Yellowstone at least it seems to happen in cycles all the time, there is evidence of this from the levels of Yellowstone lake. Currently the deformation takes shape as an uplift at an area called White lake. It is relatively small, only around 22cm in the last 53 months, but it is there. White lake GPS station is to the North of Yellowstone Lake, near the northeast rim of the Caldera.

The Hydrologic data will be an indication of activity that interacts with the water around the park, such as the heat transferred to it (around hot springs and geysers) and dissolved gases, which can inform scientists of the activity beneath the ground in the systems of water.

Enough about the basic science, lets see what can happen. Potential occurrences are eruption, hydrothermal explosions and earthquakes.

Hydrothermal explosions are basically what the name says – explosions from water expanding to steam due to heat. This can happen a lot, as there are craters from this occurring all over the area of Yellowstone. To quote the USGS YVO site:

Hydrothermal explosions occur when water that feeds Yellowstone's geysers and hot springs is explosively flashed to steam, breaking rocks and throwing them into the air. Small hydrothermal explosion events occur every few years at Yellowstone, mostly in the geyser basins, and usually pose little hazard. There is geologic evidence for a few large hydrothermal explosions, some leaving craters thousands of feet across near Yellowstone Lake and in other areas of the park. Such large explosions have not occurred within the last several thousand years.

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Earthquakes can happen due to fault lines, and most people probably know what the results of one look like by now. It's not like there haven't been many this year.

And then we reach the eruption hazard. This is probably the least likely for the next few years, but who knows? The most likely of this event would be a 'small' eruption like that of Mount St Helens, of a small volume of magma no larger than 1 cubic kilometre. I'm sure most people know what that looks like, but it looks like this:

The main hazard here is the pyroclastic flow, though ashfall and lahars can be deadly later on, but this is mostly limited to a relatively nearby area in this case.

And then there is the Volcanic Explosivity Index(VEI) 8 eruption, more commonly known as a super eruption. This would basically cover the continent of North America with ash, and pose a great hazard to everyone within that area. There is also the likely possibility of a volcanic winter (global cooling) as well in this case.

The area as can be seen in the above image is quite large. It could even be bigger, but it probsbly wouldn't be. This is, after all, the least likely of all occurrences. At the present time it's perfectly quiet, and is likely to remain like that.

[edit on 9-12-2008 by apex]