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.”).

Castle Rock

Last weekend, I hopped on my bike and made the 30 mile round trip trek (personal record for me :D) to nearby Castle Rock in order to spend some summer somewhat within my educational pursuits. Castle Rock is an exposed piece of the St. Peter Sandstone, a very mature, very pure quartz arenite formation that most geologist and students of the Midwest are likely familiar with, located between Dixon, IL and Oregon, IL on Illinois Route 2 in what is now known as Castle Rock State Park.

The St. Peter Sandstone is a Middle Ordovician formation dated between 465 and 460 million years ago, that is widespread throughout the Midwest. It’s deposition coincides with the beginning of the Tippecanoe Sequence (A Sloss sequence or cratonic sequence; a sequence that describes the transgression and regression of sea levels, and consequently deposition and erosion across a craton), a period of relatively higher sea levels covering the craton in a shallow sea; a perfect environment for the deposition of the sand that would become the St. Peter Sandstone.

The distribution of the St. Peter Sandstone formation (I live a bit north of Ottawa); taken from Mostly Maps (http://mostlymaps.wordpress.com/2009/12/20/sands-of-time/)

Approaching the park, your first glimpse of the St. Peter Sandstone is the rock exposed by the road cuts that follow Route 2 as it twists through the bluffs that line the Rock River. Unfortunately, rather terrifyingly, and much to my dismay as I had apparently forgotten, the well-traveled Route 2 loses it’s shoulder here, and the blind curves make a cyclist a rather large roadside hazard. I am happy to report that I survived, however.

There are few things of note in the next photo (I also apologize for the quality, I feel like there was something wrong with my settings this day); first, the obvious cross-bedding or more accurately cross-lamination, and secondly how loosely cemented the rock is. It’s very friable (a good word for geology students to know), meaning it very easily crumbles at the touch. It’s not very well cemented together.

The cross-lamination provides an insight into the history of the deposit; you can determine the direction of flow that deposited the sands, and you can rule out certain depositional environments based on the angles of the laminations. For instance, the cross-laminations observed at Castle Rock are very low angle; these are associated with deposition by water as opposed to deposition in the dunes of a desert, where cross-bedding is much more prominent and much higher angle.

A short way down the road from the road cuts is the Castle Rock area itself. A set of trails and some river side recreational areas. The really unfortunate thing about Castle Rock now is that the Illinois DNR  has covered it with a bunch of wooden walk ways and makes it really less than ideal for people interested in the rocks to examine them. Sample taking and climbing on the rocks is strictly prohibited in the interest of preserving the site.

It’s still possible to see some of the features of the formation however, note the lamina and bedding, and more cross-lamination’s visible here.

Below the Castle Rock, along the river there are plenty of exposures too, but most of them are inaccessible unless you have a boat, but there are some along the shores that you can approach and that have some interesting features.

In the lower right of this next photo, you can see a dark layer in between the sandstone, something that hasn’t weathered at the same rate as the surrounding rock. I have no idea what it is, and it’s so localized that it’s hard to find any other spots with the layering present and again, it’s very illegal to take samples from the area so if you have any ideas, shoot them my way. The area is clear of brush though, as if someone has spotted it before and has also examined it.

If you follow the shore south, you come across a nice face you can look at, but like I said, most of this stuff is only accessible by boat. The river is a little low right now, so I was able to get this by compromising with muddy shoes.

…and here is a nice shot of the scenic view from atop Castle Rock. It’s really a nice place to check out. It’s not a geology mecca by any means, but it’s local and a nice place to have a picnic.

Into the Woods

I was breaking in my new hiking shoes and bag (with hydration pack, woo) and decided to go running around my favorite local geologic haunt, Franklin Creek which was talked about when I first started this blog 6ish months ago.

So nothing new, just some pictures. Pictures were taken using the Android app Camera FV-5 which I highly recommend because it gives you manual control over your built in camera. So much better than the built in camera for my phone at least. Give the Lite version a shot before diving in though, it might not work with your phone. I post-processed them with Pixlr-O-Matic because I like having a common visual motif and no longer feel like touching up photos in Photoshop for long lenths of time.

Assuming the weather picks up, I’m going to do some long rides this weekend and maybe post about some other local geology. Fingers crossed!

Baraboo

I’ve neglected to update the blog for awhile, but I have good reasons. The last two weekends I have been out with classes playing with rocks, and the time between those trips has been packed with exams and labs that have consumed my spare time and sanity. I’ve come to break my silence with a post of pictures from the trip my Structure class took to Baraboo, Wisconsin this past weekend. I have a bunch of pictures from my Volcanology trip the week prior too, but those are more to sort through at the moment. Maybe this weekend.

Anyway, most of the weekend my phone was dead and my phone is what I used to take pictures, so I didn’t get a lot of pictures. I didn’t even get pictures of all the things I wanted to get pictures of (like this really awesome fold we visited). Apart from that, the trip was very busy and rushed due to the need to get strike and dip data everywhere and search for jointing and pressure solutions in the rocks we were surveying, not a whole lot of time for pictures.

These are from our first stop at Larue Quarry and our first introduction to what would dominate our trip, the Baraboo Quartzite.

This is an image from Ableman’s Gorge where the bedding in this quartzite has not only been titled vertically, but they contain beautifully preserved ripple marks.

A short way from Ableman’s Gorge you find the famous Van Hise Rock. Upon this rock you will find all kinds of cool shit (in a worlds colliding kind of way), but my favorite thing were these en echelon vein arrays that could be found throughout.  These sigmoidal structures betray the history of stresses in the rock.

These were taken in a road outcrop that exhibited amazing crenulations. This was my first time seeing something like this in person and they’re pretty incredible. They look like Da Vinci paintings with no subject.

At the same outcrop you find these foliations with a sigmoidal shape. These were formed as the block above this layer moved to the right (and slightly into the screen) and the one below to the left (and out of the screen).

Here, once again at the same outcrop, we find ripple marks spectacularly preserved in the quartzite.

In the cliffs above Devil’s Lake you will find this feature; an unconformity that represents 1.1 billion years of missing time.

… and finally, our fearless leader talking about the history of Devil’s Lake. A man both loved and hated during the trip. Good dude.

Random thoughts on Volcanology 2

Yesterday while trying to circumvent DRM, I accidentally my whole computer. So I spent all day yesterday backing up data and reinstalling Windows XP (I have XP on my PC and 7 on my netbook). I wanted to spend my time this weekend studying for my Volcanology and Structure exams, but as I’ll be out of town with those classes the next two weekends, this was my only chance to fix it. Given that my Volcanology exam is tomorrow morning, I think it’s time for another edition of random thoughts on Volcanology!

This section of the class was a little on the boring side I must say. We spent alot of time talking about pyroclastic flow deposits, which sound cool, but at the end of  the day, aren’t the most interesting thing one studies in a class about volcanoes.

Firstly pyroclastics, or ‘fire fragments’ are volcanic rock fragments. So pyroclastic flows therefore, are flows that contain a large amount of those pyroclastics.

I’ve said flows so far, but we talked about several types of pyroclastic ‘events’ in a more general pyroclastic density currents. These density currents are gravity controlled laterally moving mixes of pyroclastics and air.  From that umbrella term, you can separate them into two categories, flows and surges. These are separated by their pyroclastic content. Pyroclastic flows are more dense than surges, meaning that the ratio of pyroclastics to air is much higher. Surges are much more dilute than flows and contain more air than pyroclastics.

Furthermore, pyroclastic flows can be broken down into block and ash flows and ash flows. Block and ash flows are just what their name suggest (convenient, huh?), flows consisting of ash and blocks (pyroclastic material larger than about 64mm). These flow types are favored in Vulcanian eruptions and lava dome collapses. Ash flows travel further than block and ash flows and are generally produced in Plinian eruptions.

(I’m sorry if this ends up being hard to follow, I’m just rewording my notes and my teacher is not one for cohesive order)

Those relationships should be obvious, because Plinian eruptions aren’t going to be producing tons of blocks, but tons of ash, and the opposite with Vulcanian eruptions. Lava dome, likewise, result in the formation of many blocks and bombs leading to those block and ash flows.

Lava dome collapse is influenced by two main factors: gas pressure inside the dome and the tensile strain of the dome itself. When pressure exceeds the tensile strength of the dome, you get an explosive collapse, if a collapse occurs when the tensile strength exceeds the gas pressure, you end up with a gravitational collapse. Either way, you get a lot of large pyroclastic material released.

Pyroclastic surges are generated in sometimes similar ways, but distinctly different ways as well. Surges, if you recall, are composed more of hot air than pyroclastic material. So they can be formed by lava dome collapses, but they’re also produced by boiling over eruptions, eruption plume column collapses, directed blasts and from the base of an explosion column in the form of base surges.  They can also occur at the end of pyroclastic flows, and from the upper, less dense part of pyroclastic flows. That all makes sense when you think about it, all of those events are going to causes much less pyroclastic material than an actual eruption would as they’re almost all secondary features of eruptions.

So what are you left to find when one of these pyroclastic density currents occurs? Ignimberites, of course. Ignimberties are thick, widespread, often pumice-rich pyroclastic flow deposits that are poorly sorted and generally unstratified with a wide variety of characteristics that give us clues as to where they came from. That means it’s a lot like sedimentology and…. Zzzzzzz….

I’m tired of writing. I’m sure this was generally useless to anyone who read it. Apologies.

Down for the core.

I am currently reading this paper on some volcanic stuff on the moon. I am either really tired, or most of it’s going over my head, maybe a combination.

Today we went coring in a bog. It was a pretty cool experience. Got to do some real field work type stuff and talk about the practical applications of the things I’ve learned in my time here. Possibly got some ideas for senior thesis stuff/internship opportunities.

Spent most of the day wandering around in a couple feet of water and trying not fall over. We were going to go to two locations, but we got rained/stormed out (as it turns out, standing in a bog while holding a very tall metal object during a thunderstorm is unsafe). It also turns out that I am terrible at taking pictures as I have nothing of us actually doing any coring. Just some random pictures and some of our cores.

Now, to do geology on them.

Coring and cross-sections

Crafting cross-sections by hand is the most tedious thing I think I’ve experienced thus far in my geologic education. I’ve done a handful of cross-sections before in my geology program, but they were very basic. In my structure class, we’re now going full bore and I can confirm that it is not my favorite part of doing geology. On a tangential note, the absolute best way to take away the last bit of a student’s enthusiasm for something so tedious is to let them know that computers can do it with little fuss. I’m probably sounding really whiny, but a lot of structure lab so far seems like long, complex, boring assignments that result in a lot of busy work.

Now that Spring Break is over, our Global Cycles class switched professors and now our resident geochemist is taking over. That means doing a lot of work with stable isotopes and I think that’s going to be really cool. Tomorrow we’re going to spend the day out in the field drilling core for our lab and I’m really looking forward to it. I’ve never participated in coring, so it will be a good learning experience.

We’re going to be coring through some glacial deposits and in a bog, and since it’s going to be raining all day tomorrow, I’m sure that will be thrilling.

I didn’t sleep last night as I worked to finish my cross-sections that were due today, so I’m looking forward to sleeping right about… now.

ChaCha

Somehow, while I was looking up information on the mechanics of back-arc basin formation, I ended up on ChaCha. For the unaware…

ChaCha gives free, real-time answers to any question both online at ChaCha.com and through mobile phones by either texting “ChaCha” (242-242) or using one of our mobile apps. Through our unique “ask-a-smart-friend” format, ChaCha has become the leading answers service with more than a billion questions answered to date all in a fun, conversational format perfect for those in need of fast, free answers while on-the-go.

I ended up in the Earth Science section because I was curious, and I was disappointed with what I found. ChaCha may offer quick answers, but not particularly great or accurate answers. So to kill some time…

Q: What did Wegner argue about glacial deposits based on what he observed?

Wegner, as we ALL know, was the main guy behind the theory of continental drift. He had a bunch of lines of evidence to support this theory, and one of them was his observations of glacial deposits.

What Wegner noticed, was that when you looked at the glacial deposits of the southern hemisphere continents, they matched up across continent borders. Similarly to the way that other geological phenomenon did such as fossils, coal beds, etc.

So, Wegner argued that the glacial deposits were once part of one glacial system when the continents were once joined.

Q: Why is the World not round?

I assume this question is asking why the Earth is actually an oblate spheroid as opposed to being perfectly wrong. ChaCha’s answer says why celestial objects are generally round, which doesn’t answer the question.

The Earth is generally depicted as being perfectly round when in actuality, it is not. It’s an oblate spheroid, meaning that it’s a sphere that looks like it’s being pinched at the poles so that the equator bulges out a little bit.

This occurs because of the rotation of the Earth. The rotation of an object results in something called centrifugal force. Centrifugal force is what you’re feeling when you take a turn at speed in a car and your body wants to move to the ‘outside’ of the turn.

In the Earth’s case, the rotation of the planet is causing it’s mass to move to the outside of it’s rotation resulting in the oblate shape of the Earth.

Q: How does sand turn to glass?

This is either a geology question or a Minecraft question. ChaCha answer neither, and fortunately Minecraft takes it’s cue from real life so both can kind of be answered at once. Sand, well, mature sand, is compositionally almost entirely composed of silica (SiO2) which is the chief component of glass.

You can read about artificial glass making somewhere else, but sand can turn into glass naturally by lightning strike. Glasses are created through a process called vitrification, and a lightning strike can cause this vitrification. When this happens it forms vein-like structures called fulgurite.

It might not look like what you think of when you think of glass, but there it is. Natural glass.

In Minecraft, you take sand, put it in the furnace, add coal and vitrify.

Quiet

I took this picture today while I was sitting in the physics building. I really love it. I sit there almost every time I come to the building and today was the first time I’ve ever looked up. It was the perfect opportunity to misuse panorama.

I haven’t posted much lately as I’ve been drowning in school stuff. I took my 2nd Structure exam today and I think I did very well on it. I wrote a pretty comprehensive study guide for the exam and every question on the exam was answered somewhere in it, so I think I got most of the points.

I also got my Volcanology exam that I took on Friday back today. Walking out of the exam I didn’t feel too great about it, but I did well enough apparently. I’ve still got my A in the class.

Tomorrow I’ve got a Global Cycles exam, and I need to finish up Structure and Physics labs tonight at some point. Then– I need to start studying for Friday’s Physics exam.

I’m really looking forward to Spring Break. I’m going to ride my bike as much as possible, dive into my term paper for Volcanology and relax.

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.