Two Shallow Quakes Hit Mammoth Mountain

Mammoth Mountain in California (located between Yosemite National Park, and Long Valley Caldera/Inyo Craters) is more commonly known locally as a ski/snowboarding resort, but few people actually realize it is a dormant, and potentially active volcano. Two shallow earthquakes, both less than 2km in depth, occurred near the summit of the restive giant. However, this does not indicate any impending eruption, although the quakes are likely tied to volcanic activity.

Map from USGS/CALVO detailing the locations of the most recent quakes at Mammoth.

Mammoth Mountain has not erupted in historical time. The last eruption was approximately 700 years ago, and occurred on the North side fo the mountain from vents that issued lava flows. The only other recorded activity since then, was a minor dike intrusion in 1989 that caused CO2 gas to be released at the SE foot of the mountain, killing a forest worker, and tree kill is apparent in the area to this day. The fact that the tress have not recovered, and CO2 gas is still present has prompted warning signs to be posted int he area since the incident, and the area remains off limits to people.

 Typically, there are a few quakes in the region yearly, but most of them are not near the summit as these two were, so it begs the question, is Mammoth Mountain slowly gearing up for a show?

An eruption at Mammoth Mountain might bode poorly for residents of California. Mammoth is a popular tourist attraction for skiers and snowboarders, is next to Yosemite National Park, and some evidence suggests a correlation between activity at Mammoth, and Long Valley Caldera (although Mammoth, even though it is situated on the NW rim of the Long Valley Caldera, is a chemically distinct magmatic system from Long Valley). An eruption today would likely be either phreatic (maar forming when ground water flashes to steam once it hits hot rock/magma), or an explosive cone forming eruption, much like its cinder cones to the south. However, Mammoth is a diverse volcano, having created lava domes, maars, and cinder cones, so any future activity could take many forms, however none are particularly life threatening if people are evacuated in advance of new activity.

The are has experienced a heightened level of seismicity (which includes Long Valley Caldera) since the mid-1970's. Causes of these quakes range from volcanic activity, to crustal adjustments (much like the recent quakes at Mauna Kea in Hawaii), or tectonic stress. In this case it is likely both a combination of crustal adjustment from the 1989 magma dike intrusion, and/or further injection of magma into the system are occurring. Magma dike intrusion does not always (and actually, not often at all) result in an eruption from a volcano. 90% of the time, the magma dike will cool slowly below ground, never breaching a seam or crack that would allow the lava to quickly decompress and erupt. So if this was actually dike intrusion, we might see more gas released like the 1989 event, or nothing at all.

CALVO is monitoring all volcanic systems in California and Nevada now, and have received new funding for furhter installation of scientific instruments on the most concerning volcanoes, including Mammoth Mountain. The project is not done yet, and monitoring on several of these volcanoes is done currently through the existing network. In the future, CALVO plans to install more detailed monitoring equipment that will measure gases, fumerole temperatures, harmonic tremor, and other factors that are currently unavailable for some volcanoes. 

Seismicity Picks Up At El Hierro

El Hierro Island in the Canaires made headlines last year when a submarine eruption occurred less than a mile off the coast of the fishing village of La Restinga, creating an underwater cinder cone, and providing a demonstration of a Serretyan eruption (An eruption consisting on gas filled lava 'balloons' that burst at the ocean surface in a puff of flame, only to sink to the ocean floor and pile up) that thrilled scientists and other volcano enthusiasts. The eruption technically ended some time after the government said it did, but lately seismicity has been picking up and the epicenters of the quakes appear to be getting shallower.

As far as the folks over there at Earthquake-report.com are concerned, they have been on top of things from the get-go with a 'reporter', Joke Volta, on the ground, taking daily pictures and reporting on any earthquakes or changes.

The last few days have seen on average 5-10 smallish quakes, with some larger (mag 4.0 and up) earthquakes. When the seismic swarms resumed, the depths and locations of the quakes were fairly consistent, with most being at the Western tip of the island, 20km below a lighthouse. These quake swarms have now migrated to the center of the island in the area known as El Golfo (the area that resembles a crater, but is actually the result of an avalanche thousands of years ago), and are now occurring at shallower depths (the latest swarm is taking place at a depth of around 12km).

INVOLCAN and PEVOLCA, in conjunction with ER seem to believe this is indeed related to magma dike intrusion at this time, and preparations are underway to possibly raise the alert level of the volcano again from "Green" back to "Yellow", but this is only preparation and precaution, and as of now there is no cause to actually raise the alert level, although I suspect if the quake swarms continue for a lot longer, we will probably see the alert level raised, and maybe even another eruption from the island.

Deformation on the island lately has been stable, although since the end of the last eruption, the island has been uplifted some 10cm! This clearly indicates magma rising in the chamber. Some subsidence has occurred, but for the most part the island right now is stable. Time will tell what the results will be.

*****UPDATE 8/17/2012*****

Earthquake-report.com is reporting over 58 quakes have occurred in the last day in the El Golfo region of El Hierro.

Large And Shallow Earthquake Swarm Near Aniakchak Volcano

Aniakchak volcano in Alaska is one of the largest, and most active volcanoes in the Aleutian arc. The volcano contains a 10km wide caldera, with multiple cinder cones occupying the ~3400 year old caldera floor. The last eruption of Aniakchak occurred in 1931, which marked the only known historical eruption of the volcano.

A large earthquake swarm struck approximately 25 miles NE of Aniakchak on August 3-5, centered between Aniakchak volcano and the lesser-known Yantari volcano (which apparently had a very Mt. St. Helens like eruption in pre-history). The largest quake was a 4.7 magnitude quake at a depth of around half a kilometer (which is very shallow). Many other shallow quakes, some with similar magnitudes have occurred (see the below image) since.

Google Earth plugin with USGS real-time overlay enabled showing the location of the quake swarm

The depths of most quakes in the area are usually some hundreds of KM deep, as this is a subduction zone where one plate slides underneath the other. Occasionally this process generates a magma vein, that results in dike intrusions and the birth of most of the world's stratovolcanoes.

This quake swarm is curious due to its location and the very shallow depths. New volcanoes have been born in Alaska in the past, sometimes with disastrous results such as the eruption of Novarupta, the largest eruption of a US volcano in recorded history. While it is likely that this is a magma dike intrustion into the crust, it is impossible to say what might occur if the swarm does not return, or no new magma is injected into the crust. Most dike intrusions do not result in an immediate eruption, and some times they never do.

In any case, I will be keeping a close eye on this, and possibly email AVO about the swarm and see if they were aware of it (which I am sure they were) and whether they might be able to shed some light on it for our readers. Stay tuned!

*****UPDATE 8/9/2012*****

Another single quake at a depth of 5km measuring 2.5 occurred today in the area. This is the first aftershock/tremor in a few days. I have contacted AVO requesting information on the current swarm, and hopefully will hear back from them soon!

*****UPDATE 8/10/2012*****

AVO responded to my email with the following response:

"They're regional tectonic earthquakes. We have no indication that these earthquakes have anything to do with volcanism.This series of earthquakes, at this time, is not alarming to us."

So it appears that there may be several faults criss-crossing the Aleutians that occasionally have these shallow types of quakes occur, even very near active volcanoes.

Swarm Of Quakes Rattle Los Angeles, CA

A series of moderately sized earthquakes and associated aftershocks hit the Los Angeles (Yorba Linda) area in California today and yesterday, with two quakes registering 4.4 and 4.5 on the Richter scale being the largest tremors. Residents as far south as San Diego County reported feeling the quake, and near the epicenter it was reported to feel quite strong. The quake depths were from 10km-8km for the largest tremors. Many shallower aftershocks, most at or around M2.2 (but some at 2.9) have occurred, and are still occurring as of now.

Los Angeles is no stranger to earthquakes, and as such, has building codes that normally prevent any damage. In California, most buildings must be built to be able to withstand up to a magnitude 8.0 quake as a building standard.

Interestingly enough, the quakes did not occur on the famed San Andreas fault line that extends from Baja California, Mexico, to central California in the US. These quakes occurred some 35 miles SW of the nearest point to the fault at Cajon Junction. These quakes occurred on a smaller fault that runs under Yorba Linda. This fault line is quite small compared to its larger, more violent neighbor, the San Andreas, running only tens of miles in a NW/SE direction. (Given that this is a volcano blog, I should note that these quakes are in NO WAY related to any type of volcanism).

It is likely that more smaller aftershocks will follow for a few days in the area as the fault settles down. It is possible that these quakes may destabilize other faults in the area, however at this time this is only a 'maybe', as scientists still struggle to really figure out how parallel faults affect one another. Earthquake dynamics are highly complex with many factors that go into causing them, and even more factors in the aftermath to consider. 

New Concerns About Campi Flegrei in Italy

There are less than 20 so-called "supervolcanoes" on Earth, and of those some are well known, and some are not. From Yellowstone to Taupo, Toba to Uturuncu, and more, we know that these volcanoes erupt with extreme volatility, yet very rarely... with the exception of some. The most recent magmatic eruptions from any known supervolcanic caldera has occurred in the Aira caldera in Japan, where the resurgent Sakura-Jima stratovolcano has been erupting in the center of the caldera for many decades. The most recent actual supervolcanic eruption (VEI 8) occurred over 75,000 years ago at Lake Toba volcano in Indonesia, which, according to widespread genetic analysis, may have reduced the modern human population to under 5,000 individuals worldwide (although the maximum population at that period has never actually been quantified).

Indeed, supervolcanoes are a terrifying thought, however these events are so rare, and nearly unpredictable (according to current science) that one should not even sweat one drop worrying that this may occur...

But this is not the case in Italy, as the Campi Flegrei volcano is again in the media spotlight (as occasionally Yellowstone or Uturuncu is when news outlets want some ratings).

As I have reported previously on this blog, Campi Flegrei is the site of a study that seeks to better  understand the dynamics and goings-on in the magma chamber beneath Pozzouli, Italy. The area boasts a population of over 3 million people, and any eruption from the restive caldera would be of grave concern to the government, and to the population. As recently as 2010, industrial drilling has taken place at the volcano, however once scientists proposed a drilling operation that would reach the magma chamber, unfounded concerns by non-experts forced the operation to be on hold until recently.

Now, a team of geologists will drill some 3.5+ km into the magma chamber in an effort to monitor and detail the dynamics of one of the world's most active super volcanoes. The last eruption from the Campi Flegrei field produced the Monte Nuovo cinder cone in 1538, which was documented thoroughly by local witnesses of the time. Earlier volcanism produced several solfatara fields, and modern-day activity has consisted mostly of fumerolic/phreatic activity, and gradual uplift of the caldera area, which in the 1980's prompted evacuations of some areas due to the rate at which the land was rising.

Current uplift has left some modern and ancient nautical ports/docks inaccessible due to he gradual and constant uplift of the land. In one port, the land has risen so much that the cement boat launch platform that used to serve the area pre-1970 is now so elevated that you might consider using it as a diving platform rather than a place to launch your boat.

Campi Flegrei is monitored by the Vesuvius volcano observatory in Italy (Vesuvius, another powerful and notorious volcano is located a mere 15km East of the Campi Flegrei Caldera), and lately, no warnings have been issued in regards to seismic swarms, magma intrusion, or increased fumerolic or solfataric activity in recent memory.

There is not enough data that currently exists at this time to say what the next phase for this sleeping giant would be, but most sources that know what they're talking about would tell you this: A super volcanic eruption is a rare event, which requires rare circumstances. The conditions at Campi Flegrei, and every other super volcano in the world suggest that while we are now aware of the existence of such volcanoes, we should sleep well at night knowing that none of them are currently capable of producing the conditions for such a natural disaster. Not even Yellowstone.