El Calderon at El Malpais

On our trip (of which only 1/3 of participants was a geologist) we were able to make a quick stop at the El Malpais National Monument. This area is renown for it’s rich volcanic terrain and as a studying geologist that’s interested in volcanology and potentially will be visiting the area again this Fall in an expanded capacity, I was really excited to check some stuff out. Our time was limited, so after stopping by the visitor center we decided on a short little hike that would let us see some lava tubes and a volcano.

The area we decided upon, at the ranger we spoke too’s suggestion, was El Calderon. El Calderon is a cinder cone volcano that was formed around 115,000 years ago from lava fountain style eruptions. Sometime after the fountaining stopped, the eruptions continued in the form of fast moving basalt flows that carpet a wide area in the vicinity today. This period of basalt flows leaves a jagged terrain of vesiculated rocks, but more interestingly to me, a geology enthusiast from the flatlands of Illinois, it left behind the tubes by which that lava flowed all those years ago.

You can see on the poster above (maybe) that these tubes are now closed off to the public to protect the bat poulations from the threat of White nose syndrome.  Fortunately for us, there are smaller, partially collapsed lava tubes available to traverse on the El Calderon trail, and traverse it we did.

It’s really dark inside the tubes, so these were the only images I was able to grab, but it was a really cool experience. I wish we had the time and permission to go further into them. The lava tubes, when they’re open to the public, are pitch black, trail-less caves to explore.

This is a sample of what all the rock in the above images is like… It’s very sharp, jagged, highly vesiculated basalt. It’s not kind on the body when you miss a step and trip or need to catch yourself when slipping.

Vesiculation (formation of gas bubbles; and thus the holes in the above image) occurs under several conditions; increase in temperature of the lava, for example when there is an influx of newer, hotter magma; increase in the concentration of volitailes (CO2, SO2, etc.) usually by the crystallization of anhydrous (water-phobic)  minerals; or a decrease in pressure  caused by the ascent of the magma/lava. In the case of El Calderon, the lava flows were apparently very fast and moved long distances quickly so I think it’s  case of the latter, where the lava quickly made it’s way to the surface and became highly vesiculated in the process. I also could be way off, I have almost zero background information beyond a few brief web pages.

After we exited the lava tubes, we made our way to El Calderon itself with every intent to get to the crater. Teejay is doing some sort of crip-walk or something here apparently.

Unfortunately, shortly before reaching the base of the volcano, there was a fence, a gate and a Private Property sign. That seemed odd, so we think we took a wrong turn somewhere, and in the interest of time, we had to turn around and head back to our car.

The whole experience made me really excited to head back there sometime though. I would love to spend some time in the field there and observe many of the phenomenon that I’ve only read about and seen in picture.

ALSO: Nearby is the Bandera Volcano and Ice Caverns and their website said they opened at 8am, so we showed up at 8am. When we got there the sign said they opened at 9am. FUCK EM. We went here instead after that (The other place still sounds super awesome though, so fuck em in the sense like “Damn! I really wanted to go!” not “Fuck those shitty assholes.”).

Random thoughts on Volcanology

I am currently studying for a Volcanology exam I have in the morning. I’m going to muse about random things we’ve covered in an attempt to know them better.

Magma resevoirs

Magma reservoirs are continuous regions of magma , and serve as the magmatic source for volcanism. Resevoirs are made up of two key components: the magma chamber, and the magma mush. Typically magma reservoirs are described or depicted simply as a magma chamber, but within what people commonly view as the chamber, there is a zone called the mush.

The magma chamber is the zone where eruptable magma is stored, eruptable meaning a non-rigid supply of magma. Generally, if the composition of the magma contains less than 50% crystals, it is considered part of the magma chamber.

The magma mush zone exists where the magma is rigid with greater than 50% crystal content. In the image below, the magma mush is represented by where the crystals are settling.

Volume and size of magma reservoirs can be estimated by measuring the volume of eruptions in the form of lava and pyroclastic deposits. Both lava and pyroclastics were once magma within the chamber. Lava measurements are 1:1 when inferring volume of magma, converting a measurement of pyroclastic however, is more complicated.

Taking measurements of pyroclastic deposits and turning them into value of magma volume requires using the dense rock equation; (volume of pyroclastic deposit) x [(density of pyroclastics)/(density of magma)].

Indirect measurements of magma reservoirs can be made by studying seismic waves in a few ways. One way is  through the observation seismic wave attenuation. Attenuation meaning the weakening of a force, this basically means observing when seismic waves slow down as they pass through the earth. Waves will become attenuated when they pass through a magma reservoir because the magma is a liquid. Seismic waves travel faster through country rock than molten rock.

This also means that magma reservoirs can be detected by locating anomalies in seismic reflections, again because of the properties of solid vs. liquid.

The more interesting way to infer size of magma reservoirs is by analysis of earthquake foci (aka the hypocenter or the spot within the earth, at depth, below the epicenter). Earthquakes only occur where brittle deformation can take place, meaning no liquids. As volcanoes typically occur in seismically active places and can causes earthquakes themselves, you can use that information to map a magma reservoir.

The beginning of the class was focused a lot of magma compositions and tectonic settings while this part of the class has focused on eruption types. So the above may seem a little out of place but it fits.

Here’s some eruption classification junk:

Volcanic eruptions can be broadly split into effusive and explosive eruptions. Effusive meaning non-explosive while explosive eruptions are rather self-explanatory. Within explosive eruptions there are Phreatomagmatic eruptions which are explosive eruptions caused by the violent interaction between magma and some external water source.

To get more descriptive there is also the Lacroix classification system that classifies eruptions by comparing them against iconic eruption types.

Hawaiian Eruptions and predominantly effusive, with lava fountaining common and primarily basaltic lavas/magma.

Strombolian Eruptions are moderate, discrete eruptions with lavas/magmas ranging from basaltic to andesitic in composition.

Violent Strombolian Eruptions are similar to Strombolian except that they have moderate sustained explosions and have a sustained ash plume.

Surtseye Eruptions are basaltic, phreatomagmatic eruptions with a large “rooster tail” ash plume.

Vulcanian Eruptions are eruptions with moderate-strong, sustained explosions with intermediate composition magmas that are sometimes phreatomagmatic.

Plinian Eruptions are eruptions with very continuous blasts and a very high eruption plume. When interacting with water, they are the largest of the phreatomagmatic eruptions.

Outside of those classification schemes, there are also those of George Walker, which measures pyroclastic fall desposits, and the more common Volcanic Explosivity Index which is a semi-quantitative scale of eruption magnitudes using a variety of measurable quantities associated with an eruption.

I am tired now.

No moleste.

I have spent most of my day that wasn’t at school in a state of unconsciousness.

Check out these amazing pictures of volcanic things in 2011.

Fish Canyon Tuff

Exploring another volcanology topic today. The Fish Canyon Tuff.

This, like yesterday’s post, is about a very specific volcanic occurrence, not a broad topic. Tuff, for those non-geologically inclined, is a type of rock that is formed by volcanic ash as it compacts and welds itself together as it is very hot (you know, having come from a volcano).

The significance of this in Fish Canyon is that there is a lot of it. So much of it, in fact, that if you measure it, look at it’s composition and infer what kind of eruption produced it, you end up with one of the largest, most confidently estimated, eruptions in the history of the Earth.

The Fish Canyon Tuff is the result of a supervolcano that formed a massive caldera near La Garita, Colorado around 28 million years ago. A caldera forms after certain types of eruption occur. The ground rises because of the eruption and then collapses upon itself after the eruption is finished leaving a large depression. Here is a cool animation I found on Wikipedia showing off how it works.

To deposit the amount of tuff it did, the eruption would’ve had to been a supermassive, explosive eruption… and it was. The energy released for this eruption is estimated to be the most energetic event on Earth since the asteroid that struck the Earth leading to the K/T extinction occurred 65 million years ago.

Another cool topic, but I’m not sure it’s for me. I WAS thinking supervolcanos when I first learned of the paper, but some of the other topics look a little more promising. Either way, it would be a cool looking place to visit.

Ol Doinyo Lengai

I have a Volcanology class this semester. Thus far it’s been pretty cool. We’ll go to the St. Francois Mountains later this semester, and it doesn’t seem to be that heavy of a course load for the class. The only thing of real importance is the 10-15 page term paper due at the end. We were given a list of topics to choose from and I haven’t decided what I wish to do yet so I’m just reading up on different ones.

One of the topics is Ol Doinyo Lengai in Tanzania, Africa. Most of the topics on the list are on there because of some sort of interesting property about it. There are a handful of volcano’s on the list, but most of the rest of them are more general topics of interest or extra-terrestrial things.

What is interesting about this volcano is that it’s magma is of a composition that isn’t very common to most volcanoes. It’s lava is natrocarbonitic in nature, meaning it is a volcanic source for the mineral carbonatite. As most lavas are very silica rich, this is kind of cool and unique. Not having much experience with carbonate minerals, this might be an interesting topic to tackle.

This makeup of these lava flows result in unique properties for the lava, including how it flows and looks. It seems pretty neat.