Friday, August 28, 2015

Keeping an eye on Cotopaxi Volcano

- Janine

Cotopaxi volcano is Ecuador's most intensively monitored volcano. With an active past, glacier-covered summit, and surrounding population it is watched very closely by the local team of volcanologists at IGEPN.

Monitoring network on and around Cotopaxi volcano that has been growing since the first seismic station installation in 1976. Courtesy of IGEPN.

Cotopaxi started quietly rumbling to life again in April with an increase in seismic activity. A Seismic swarm on 14th of August preceded phreatic (water) explosions on the 15th, and now Cotopaxi is on Yellow Alert in a phase of near-continuous ash emission (for more details see the Smithsonian Reports).



The above video was posted on August 18th and shows white steam/gas plume emission and ash fall on the snowy flanks.


The above video shows ash emission on the 21st of August with the ash plume that did not exceed 2 km on this day. Ashfall affected the south to west, west, and northwest of the volcano.


The above video taken on August 22nd shows more buoyant ash emission drifting to the West of the volcano.

Preliminary ashfall map for the period of 15th-21st of August, courtesy of IGEPN.

Monitoring Cotopaxi's gasses from space - an Aura/OMI image of SO2 values on 24th and 26th of August.  Courtesy of IGEPN.


36 hours of ash accumulation over 24-26th of August on a seismic monitoring station in the western area of Cotopaxi volcano. Courtesy of IGEPN.

Thermal monitoring of the Cotopaxi summit. This image is of the SW-S flank, taken on the 26th of August with temperatures reaching 160 degrees celsius.  Courtesy of IGEPN.


Seismographs of elevated activity at Cotopaxi volcano on August 26th and 27th, Courtesy of IGEPN.

Seismic energy release graph showing elevated levels over the past three days. Courtesy of IGEPN.

IGPEN lists the following hazards around Cotopaxi volcano:
Pyroclastic flows (gravity currents of rock, gas, and ash)
Ash and pyroclastic fall
Lava flows
Debris (rock) avalanches
Lahars (mud and debris flows)
Volcanic gasses

Lahars are a significant hazard at Cotopaxi due to the ice and snow covered slopes. Below is a Lahar hazard map with potentially affected ares in red:

Cotopaxi volcano lahar hazards map, click HERE for original map.

The Ecuador Security twitter account is posting regular updates (in Spanish) including press releases, volcanic activity reports, preventative measures:



and their website where they post this information is found here.

You can keep an eye on the eruption yourself with the webcams, often showing the eruption plume through the clouds here. The latest GIF below was taken today (28th August at 19:48 local time):


There are many active volcanoes around the world, and many with nearby populations that may be affected by eruptions, and not too many that are as well monitored as Cotopaxi. In an ideal world with plenty of funding and resources all of these volcanoes would have a monitoring system to reduce the risk to the people that live in these beautiful locations. You can follow the excellent efforts of the monitoring team here:







Friday, August 21, 2015

In the footsteps of Apollo astronauts, literally!



-Alison 

No, really! I’ve walked in the same places that the Apollo astronauts honed their geology skills here on Earth. Actually, many a geologist has trained in locations that were used for Apollo training for the precise reason that they are great places to learn geology. Apollo training locations include a fair number of volcanoes, a few impact craters, and other barren rocky landscapes. The point of training, after all, was to prepare them to describe the rocky and otherworldly surface of the moon, and the moon is covered in lava and lots of big impact craters. 

Volcanic moon rock at the Chabot Space Center in Oakland California. Image courtesy of Wikimedia Commons.
 
I encourage geologists and outdoor enthusiasts alike to check out this list of training locations and see how many places you have been that was used to prepare the Apollo astronauts for the moon. I was pleased to note how many places I have visited. In fact, many of the training locations included not just volcanoes, but maar volcanoes! Most of these craters are in the western United States including Zuni Salt Lake (1965, 1967) and Kilbourne Hole in NM (1969-71), Lunar Crater Volcanic Field in Nevada (1972), Ubehebe crater in Death Valley California (1971), and the San Francisco Volcanic Field in AZ (1964,1969). They also visited one of my favorite strato volcanoes in Alaska, Katmai (1965-66). Which erupted in 1912 to form the Valley of 10,000 smokes


Alison at the Nova Rupta lava dome that formed after the 1912 Katmai eruption in Alaska. I believe I am petting the lava dome in this photo. Pretty lava dome.

There was one location; however, that was not a surprise: Iceland. In many ways Iceland is the ultimate geology training ground. The landscape has classic examples of tectonic, volcanic, hydrologic, and glacially modified landscapes, and they are accessible. So of course the astronauts went there. 

This geologist really loves rocks. Especially rocks in Iceland.
There was another reason I wasn’t surprised. There is a gully at Askja volcano, Iceland, where I did my PhD research, named Nautagil, or astronaut gully, to commemorate their visit in 1965. It is one of the few locations at Askja that bears a sign identifying its title, and occurs fairly close to one of the few ‘roads’ around the volcano. This summer was the 50thanniversary of the first Apollo training mission to Iceland. Two of the astronauts who trained there Cunningham (1965) and Schmidt (1967) went back for a visit this summer.

Photographs and stories from the astronaut training missions indicate that the astronauts traveled around a fair bit in Askja caldera and among the younger lava flows and historic 1875 pumice deposit.  They also visited Viti, which translates to hell, it is a maar volcano inside the caldera that contains tepid water frequented by tourists for a quick bath. The astronauts in training actually helped refine the reconstructed eruption sequence that involved Viti by simply observing that the maar’s deposits were on top of the main deposits from the 1875 eruption. 
Apollo astronauts at Askja volcano. Standing on the edge of Nautagil. NASA image.
My favorite spot that the astronauts visited was in Nautagil itself.  In fact they took a photo of one of the groups in front of a feature called the Rosa. The Rosa can be found in the in the photographs of many visitors at Askja, myself included! If you just put Nautagil into a search engine you will quickly see an image of the Rosa.  It is a fascinating circular structure in the middle of a dike (intrusion of magma that cuts through the surrounding rock). The dike itself stands tall in the landscape as the surrounding rock has been eroded away, and the Rosa is a symmetrical window through the dike. The Icelandic word Rosa means rose in English, which tells me I’m not the only one to find this feature beautiful. 

Apollo astronaut geology training at Askja volcano, Iceland at the Rosa feature in Nautagil. NASA image.
Alison for scale in the Rosa, Askja Volcano, Iceland.
 
An image of the Rosa without geologists climbing all over it. Note the radial cracks along the margins. The back of the hole is host rock.
 
What interested me most is no one had tried to come up with a formal explanation of its origins, though surely lots of visitors have pondered how it got there. Any previous theories weren’t recorded anywhere we could find. As the Rosa is close to a feature I was studying during my PhD, it seemed likely that the Rosa was related. I was studying a series of complicated dikes recording the interaction of rising magma with ice-cemented sediments and water. We called them Coherent Margined Volcaniclastic Dikes (CMVDs). I will forever kick myself for not coming up with a more catchy name, but as a grad student I wanted to make sure I wasn’t  breaking some code of serious geology or accidentally confusing my audience. So it got a very descriptive name. 
 A particularly photogenic coherent margined volcaniclastic dike. You can see that it has solid glassy margins with an inside of fragments of various sizes. The dike cuts through the surrounding sediment. If the host sediment was just wet it would have been difficult to preserve the dike margins, but the fragmental inside requires available water. This suggests that the sediment was frozen when the magma arrived.

Anyway, the dike that hosts the Rosa is one of dikes that has textures that indicate that it interacted with wet/frozen sediment. These textures occur about 100 m (~300 ft) further west in the same dike, and we estimated all of these features were formed fairly close to the surface. At the time this dike formed, Askja volcano was erupting under ice, so there was lots of water around. What we suspect formed the Rosa was trapped water, either water that was present in the sediment itself, or a block of ice that fell into a fissure between batches of magma. This water was heated up by the magma, and expanded, as water vapor does, to form the circular feature. The water may have been in the form of ice, ice cemented sediment, or liquid water. For more detailed discussion you can see my paper on it here. It is less likely that the water entered the dike from the margins / sides because of the intact nature of the glassy margins, and the preservation of a very thin texture called peperite. This micro-peperite further supported our model of frozen sediments by the dike. When dikes interact with wet sediments these peperite texture typically are centimeters to meters wide. In this case the dike only melted a few millimeters of the icy host, and meaning that there was less water available at the sides than would be available from above.
 
Model showing the steps of CMVD formation with some conjecture about the formation of the Rosa at the bottom. A-1) Chill margins form along a rising basaltic dike. The ice-cemented host and overlying ice fracture. The gas driven pulses of magma depressurize near the host/ice/meltwater interface. A-2) Dike drainage creates space, allowing downward flooding of the water into the dike fracture. A-3) Meltwater and magma interact non-explosively, forming a slurry. A-4) Later pulses interact with the slurry; mingling continues. B) Motion of magmatic gas, steam and clasts develop near-vertical flow banding. A final pulse is chilled against the interior, resulting in radial cooling cracks. Evidence of the preceding steps may be preserved in the CMVD (labels). C) Formation of a very thin peperite between chill margin and ice-cemented host. D) Formation of the Rosa may have involved an iceblock, a block of ice-cemented host sediment, or wet sediment. Adapted from Graettinger et al. (2012) JVGR vol 217 doi:10.1016/j.jvolgeores.2011.12.008  
The interaction of magma with water is common theme in my research. What makes it interesting here is that we can partially reconstruct the environment in which the volcano erupted. This evidence of water and ice can be beneficial to our understating of how these volcanoes grew, but also what the climate was like at the time of the eruption. In fact, in Iceland where eruptions frequently bury more common paleoclimate proxies like lakes or glacial deposits, the volcanoes themselves serve as a the major record of the position of ice during the last glacial period. More on that will have to wait for a later blog post. 

Investigating these interesting deposits  was a great way to test my creative thinking during my PhD. Askja was certainly an inspiring place to work, and it the knowledge that many other explorers, geologists and outdoor lovers have spent time learning about the Earth (and the moon) there added to the ambiance. But there are always more questions to answer! One of my goals is to experimentally recreate some of these near surface magma water interactions at our large scale facility at the University at Buffalo. So hopefully in a few years I can write a new post that improves my hypothesis about the Rosa!


 

Wednesday, August 5, 2015

Volcanoes inside and out. Or how your intro text book lied to you.

 -Alison

It can be very exciting to watch an erupting volcano or look at super fresh deposits. You get to see rock that was inside the earth days to moments before. The inaccessible becomes accessible, and in a dramatic way.
The author touching fresh rock from Kīlauea Hawaii 2009.
While I love watching active processes and fresh rock, I also love looking at rocks that have been sitting on earth's surface for millions of years waiting to share their story. The exhumed insides of volcanoes provide a great opportunity to see a more complete history of how a volcano grew. One of the cornerstones of volcanology is understanding what volcanoes have done in the past, that way we can better understand what might happen in the future. While a regularly erupting volcano like Stromboli or Etna gives us an idea of the most frequent processes, we need to look at older volcanoes to get an idea of the range of eruption types and sizes and to understand their long term growth. 
 
Earlier this summer I took a field trip to Colorado and Arizona to look at the exposed guts of two very different types of volcanoes. The aim was to investigate how magma gets through the crust and to the surface. At an active volcano we cannot see the plumbing system directly, but if we could it might help us know where the melt would reach the surface and how much was left. Geophysics is the remote study of the earth’s interior using different rock properties, such as seismic wave speed, magnetics, gravity and electrical conductivity/resistivity. These techniques have given us a way to image what is happening under a volcano, but in order to make the models precise and accurate we first need some knowledge of what is reasonable. If we’ve never seen inside a volcano, how do we know what is possible, let alone happening at a specific volcano? This is where eroded volcanoes come in.


So what about those drawings in our introductory geology text books where there is a magma chamber and with some sort of straw like conduit taking magma to the surface? Well, the honest answer is we had to start somewhere.
 
Classic drawing of a volcano and its basic parts. 1) Ash plume, 2) conduit, 3) falling ash, 4) layers of older volcanic deposits, 5) older rock, 6) magma chamber. © Sémhur / Wikimedia Commons, via Wikimedia Commons
 
It is always a good idea to start out with the simplest model, however, it is now recognized that volcanoes have much more complicated plumbing systems, but the systems are so complex that no one drawing would do to cover all volcanoes. That’s ok, it means we have more to learn, and there is work for future volcanologists!


But there is a misconception that I wish to correct. It is usually right next to the drawing of the simple conduit drawing. The text books bring up examples of ‘plugs’ or ‘frozen conduits’ of a stratovolcano, and most of them show a picture of Ship Rock, in New Mexico, USA.
 
Ship Rock New Mexico, USA. The top image shows a dike (intrusion of magma that cuts through existing rock layers) leading to Ship Rock in the distance. The lower image is the author with the ~1500 ft (480 m) tall Ship Rock in the distance. It is protected land in the Navajo Nation, so we enjoyed the view from the highway.


The sharp craggy rock pokes up out of the desert, rising a little over 1,500 feet  (480 m) from the surrounding rock. Ship Rock also has several dikes, or intrusions of magma that do not follow local bedding, that radiate away from it in multiple directions. It is pretty impressive to behold and is a great example of the exhumed insides of a volcano. The lie the intro book is telling is that it represents a plug of solid material that cooled inside a classic stratovolcano.

Ship Rock as viewed from space, courtesy of Google Earth. You can see the central structure that stands up like a ship's sail in the center and the radiating dikes. The black line indicates the approximate size of the central structure


So what is it then? It is actually a pipe full of debris, bits of cooled magma, broken sedimentary rock, and more intrusions. Ship Rock is a diatreme, which means it would have been below a maar volcano. The ground surface was likely several hundred feet higher than it is today, and when rising magma interacted with water on its way to the surface caused a series (10’s to 100’s) of explosions underground. These explosions form a crater at the surface (the maar crater) and a downward facing cone of debris underground (the diatreme). This debris has enough hot sticky magma in it, and hot water moving around, that it ends up much stronger than the surrounding rock. As the landscape erodes the diatreme and the solid intrusions of magma that fed it (the radiating dikes) are left behind, standing proudly above the horizon. Other examples of exhumed diatremes are present in Arizona (the Hopi Buttes Volcanic Field in the Navajo nation), Germany (parts of the Eifel volcanic region), Montana (Missouri River Breaks) and a few more. Maar diatreme volcanoes typically form as a result of one or only a few eruptions and have a narrow range of compositions within a given volcano. Most of them are basaltic (or a similar low silica melts like basanite or monchiquite).



Two of the diatremes from the Hopi Buttes Volcanic Field, Navajo Nation, Arizona, USA. These are both about 150-200 m tall and represent rock that formed ~300 m below the Earth's surface in a diatreme as the maar volcano formed. Top: Standing Rocks East. Bottom: Standing Rocks West*.

The drawing that should go next to Ship Rock would look something like this! A) Maar-diatreme volcano showing all the major components including the mix of debris in the diatreme that forms under a crater at the ground surface. B) An eroded diatreme butte exposed millions of years after the eruption ended.


The diatremes in the Hopi Buttes Volcanic field are exposed to form all sorts of interesting shapes. This double butte in the distance is just one of hundreds of features in the area. The lower image is of a dike, part of the complicated magma plumbing system, at the edge of a diatreme.

 
So what does the inside of a stratovolcano look like then? Summer Coon in Eastern Colorado is an excellent example of an eroded stratovolcano. The structure stands out really well even in Google Maps.  
 
Summer Coon just outside of Del Norte Colorado, USA. The map on the left is the terrain map from Google and highlights the important structures. You can see radiating linear features (dikes) and a circular outline. These structures are dipping beds of pyroclastic rocks from the sides of the volcano before erosion. The current level of erosion is close to the original ground surface when the volcano formed. The image on the right is from Google Earth in natural colors. You can still pick out the intrusions and the main structure is highlighted with a black line.


You can see a circular feature with lots of radiating intrusions, just like Ship Rock. Only now, the intrusions are predominantly inside the structure, and the circular feature is actually part of the sides of the old volcano and dipping outwards. You can imagine extending these dipping features upward and making a typical conical volcano. If you look closely at these dipping beds they are composed of a wide range of deposits, from pyroclastic flows, to breccias, to lahars, just like at a typical stratovolcano. The intrusions are also made up of a wide range of compositions, which is common at a stratovolcano. They typically have a life span around 200,000 to 2 million years and have injections of multiple batches of magma. A few undergrad field camps spend some time here, so a fair number of geologists have spent time there. 

View from inside Summer Coon volcano looking out. This feature is a rhyolite (high silica lava) dike and about 10 m in diameter. The basaltic dikes from Ship Rock were about 1 m in diameter.


So what is the big deal? Why does it matter that Ship Rock and Summer Coon are different? While we could talk about a few issues, the one I am interested here is the plumbing system. How does the magma move through the volcano to the surface?  In the diatreme the magma explodes before it ever gets to the surface and creates a crater by breaking up the surrounding and overlying rock. When the explosions are shallow they throw debris into the atmosphere and have a plume and some other hazards similar to other explosive eruptions. The stratovolcano builds upwards, piling up its deposits to form a cone. In the diatreme the magma arrives and mixes into the debris-filled mess that is the diatreme. In a stratovolcano the magma can intrude into the conical pile of deposits and erupt at the top, like we expect, or anywhere along the side where it finds an easy way to the surface. We have a lot to learn about where an eruption is likely to occur next, and investigating these systems that were once underground is a great way to study some of the possibilities. Eroded volcanoes also give us a chance to see some of these underground structures in 3D, a unique opportunity to remember that magma doesn’t just move in a straight line from inside the earth to the surface, but can take more complicated paths to the surface. This is a good reminder for all of us who spend time looking at two dimensional sketches of these typically hidden structures.

Both of these locations are gorgeous to visit for geology, weather, and the general landscape. But there are many more examples around the world!



* If you want some really neat technical descriptions of diatremes from the Hopi Buttes area I refer you to some scientific papers. 

Hooten JA, Ort MH (2002) Peperite as a record of early-stage phreatomagmatic fragmentation processes: an example from the Hopi Buttes volcanic field, Navajo Nation, Arizona, USA. . Journal of Volcanology and Geothermal Research 114:95-106

Lefebvre NS, White JDL, Kjarsgaard BA (2012) Spatter-dike reveals subterranean magma diversions: Consequences for small multivent basaltic eruptions. Geology 40:423-426

Lefebvre NS, White JDL, Kjarsgaard BA (2013) Unbedded diatreme deposits reveal maar-diatreme forming eruptive processes: Standing Rocks West, Hopi Buttes, Navajo Nation, USA. Bulletin of Volcanology 75:739

White JDL (1991) Maar-diatreme phreatomagmatism at Hopi Buttes, Navajo Nation (Arizona), USA. Bulletin of Volcanology 53:239-258