Quake Swarm In SW Yellowstone Caldera

A minor earthquake swarm of upwards of 30 events has occurred in Yellowstone National park, just SW of the rim of the caldera, and just inside the Island Park caldera. The events were at depths ranging from 20km-9km. This could indicate a small injection of magma into Yellowstone's upper magma chamber, but could also be nothing more than crustal adjustments.

Yellowstone's magmatic system is considered to be in two distinct parts. The first, deeper part is the actual mantle plume, which stretches to the NW into Montana (or rather far under it), with the second, shallower (3-5km deep) magma chamber that is actually responsible for the hydrothermal system being much shallower. Volcanogolgists consider the shallower magma chamber to be made of a 'crystal mush', or slightly cooler magma that is only partially molten. This chamber gives off plenty of heat, and is the cause of the geysers in the national park.

An injection of fresh magma into this chamber from the mantle plume would give some cause for concern, and would heighten the chance of an eruption, however probably not an eruption of massive proportion that most people fear from Yellowstone. Indeed, while Yellowstone is responsible for some of the world's largest eruptions in prehistoric times (the last 'super-eruption' being somewhere around 600,000 years bp), it can and does produce much smaller eruptions such as phreatic explosions.

It is likely that this is normal behavior for Yellowstone, as yearly, it produces plenty of volcanic earthquake swarms. If this was a magmatic intrusion of any kind, it will likely not manifest on the surface, as the magma chamber is literally humongous, and such a small amount of magma, if any, that is injected would be like a drop of water into a lake.

The quake swarm appears to only have lasted one day, and so far has not produced many aftershocks, which is what leads me to believe that this is probably at least a small dike intrusion, or some mantle plume activity (possibly an underground collapse at great depth). In any case, I'm always looking for a good excuse to write about Yellowstone, as it is a fascinating, beautiful, and potentially terrifying volcano. If anything further develops, you can be assured I will cover it!

Below is a picture of the current swarm from Google Earth/USGS.

                           

New Info On Yellowstone Suggests "Super Eruption" Was Two Smaller Eruptions

Yellowstone volcano has long thought to have had a large super eruption over 2 million years ago, but new evidence is suggesting that while 2 million years ago Yellowstone DID erupt with a VEI 7 or 8 eruption, it was not as big as once thought, and was followed 6,000 years later by a smaller eruption. The result was an ash layer that appeared to be one layer but was actually two. This suggests that Yellowstone is NOT as powerful as once thought, but is more active.

The study revealed that the Island Park Caldera is actually much more active than previously thought, and the new information might assist scientists in better predicting an eruption from Yellowstone, given that the timeline has now changed. The last magmatic eruption in the Yellowstone caldera was some 70,000 years ago, and an episode of phreatic eruptions that created a 5km wide crater (now Yellowstone Lake). 

Scientists were using a new "Rock Clock" method to determine the ages of ash and rock layers within the Huckleberry Ridge, and were surprised at the data they found. The data suggests that Yellowstone's explosive eruptions were around 12 percent weaker than previously thought, but smaller eruptions are actually more numerous. The last eruptive activity of any kind in Yellowstone occurred somewhere around 1350BC (give or take around 200 years), and was limited to hydrothermal eruptions.

Knowing when, or how, Yellowstone might erupt in the future is one of volcanology's biggest challenges, given the impact an eruption from Yellowstone might have. But the new data seems to shrink the idea that Yellowstone is capable of a world-ending eruption (one thing I highly disagree with most scientists about is that any event on earth is capable of wiping out 'all life'... life did not simply get wiped out and reappear on the planet, there are always survivors). Indeed, the new data seems to suggest that Yellowstone is not capable of "blotting out the sun worldwide", but is still a very dangerous volcano to anyone within about 100KM.

This is good news for anyone who was worried that Yellowstone could be a 'world ender', and probably bad news for anyone who wants to scare people into doomsday nonsense for the tabloids. An eruption from Yellowstone today would likely be much weaker than previous eruptions, given that as far as anyone knows, no new magma has been introduced into the Yellowstone system for a very long time. Scientists theorize that the current magma chamber consists of partially cooled magma known as 'crystal mush', and any eruption would likely result from water flashing into steam when it seeps into hot rock (a phreatic eruption). These types of eruptions are short lived, and very rarely pose a threat outside of 1km, but anything is possible.

In any case, this new info will definitely be helpful to understanding further the history and potential of the Yellowstone caldera.