Students look on as augers advance the soil boring

During this “Field Workshop”, students were able to learn soil & groundwater sampling techniques, how to describe, classify, and log soil borings, the basics of well installation, and basic monitoring equipment.

While the equipment used it typical mostly in the environmental and engineering fields, the basic concepts apply to subsurface investigations in a wide range of applied geology fields including economic geology (natural resource exploration/recovery).

The lead section of hollow-stem auger

The demonstration we provided by a local drilling company, HAD Drilling, Inc., free of charge to our student chapter of AEG.  As such, the activities were limited to a single soil boring which was taken to a depth of only 10 feet below ground surface.  This may seem too shallow to really learn anything and, were this a real project, it would have been.  However, we were actually able to see nice examples of different soil types (clay, silt, and sand), as well as markers such as saturated seams.

Close up of an open split spoon with sample of low-plasticity silt (ML) with med-coarse grained sand at the very end (right).

Drilling is done with a hollow-stem auger (HSA), which is exactly what it sounds like.  During active drilling, a center bit is lowered into the HSA to help drill down and to keep soil from filling in the augers.  Whenever a sample needs to be collected (typically every two feet), the augers are stopped, the center bit is pulled out, and a device called a “split spoon” is attached to the end of the center rods and lowered through the HSA where it is “hammered” into the soil.  The split spoon is essentially a metal tube which can be split in half to easily view and collect the sample.  The hammering process is referred to as the standard penetration test, and is useful in determining a general density of the material being sampled.  This test is standard because a specific weight is dropped (free-fall) from a specific height onto the rod, driving the split spoon sampler into the soil.  Each blow of the hammer is counted, and the number of blows needed to drive the split spoon six inches is called a blow count.  The blow count (or N-value when you use combined blow count values) is what tells you whether the material you’re sampling is soft, stiff, very stiff, etc. (for granular material, you’d say loose, dense, very dense, etc.).

Students inspect a piece of the sample after logging its position in the soil column. Yes, they broke it apart, too.

During this sampling procedure, students were given blank soil boring logs and asked to describe each sample. Initially, they did this on their own and (purposefully) with no guidance.  They then compared “answers” and found that, while most knew they were looking at a clay, other properties of the sample varied – sometimes drastically – between individuals.  When the next sample was collected, they were given a handout which included the Unified Soil Classification System (USCS) as well as a field guide for soil and stratigraphic analysis.  The field guide portion outlined important information to include in any detailed description, such as relative density, color, classification (from the USCS guide), moisture and so on.   Now, most descriptions varied by little from student to student.  By completing this hands-on activity, they were realizing the importance of standard descriptions.

Spectacular scan of the Unified Soil Classification Chart

Groundwater monitoring and sampling methods were also discussed, as well as explaining the significance of “static water level” (aka, the potentiometric surface of the water table; aka, the level to which groundwater will rise when subjected to overburden pressure), how to use the elevations of the static water level in multiple wells to create a groundwater flow map, and how pumping tests and slug tests work to allow a calculation of hydraulic conductivity.

Beginning to draw (expertly, I might add) cross-section of a soil boring and well, as well as explain static water level, groundwater flow maps, slug tests, etc.

This activity was designed as and introduction to some of the processes students will likely encounter upon starting their first jobs.  Even if the exact practice is modified in some way (generally deeper, larger-scale explorations in rock), the basic concepts learned during this workshop can easily be applied to their individual positions.  I did keep this fact in mind throughout the presentation and made it a point to explain differences whenever I could such as how planning where your soil borings/rock cores will be located changes dramatically based on the type of project you are conducting (environmental remediation vs. gas/oil exploration vs. geotechnical investigation).

The whole crew in front of the drill rig (minus the drillers who, not to my surprise, declined the invite to join in).

Ok, this is all well and good, but why do we care to learn about this stuff?  Aside from the attending students wanting to gain a little familiarity with something they might end up getting paid to do, it’s because subsurface investigation is key to any applied geology field.  Of all the course field trips I took as an undergraduate, I can only think of one that even came close to teaching material I’d apply to my job once I graduated.  I have always wished there were more of those trips teaching me what I could expect to do in a career as a _______ geologist (fill in the blank).

Yes, yes, YES!  You need to have an excellent understanding of earth processes, geophysics, geochemistry, hydrogeology, geomorphology, mineralogy & petrology, structural geology, stratigraphy and a whole gambit of other geology subdivisions – some more than others depending on your specific field.  But even with a very strong understanding of the concepts and theory behind it all, the actual practice of getting out of the classroom and observing and doing is invaluable to students nearing graduation and beginning their job search.  That is why we care.  That is why I care and am excited to share this experience with you.

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Special thanks to HAD Drilling for donating their time and labor to giving such a great experience to our group of future geologists!

Extra special thanks to my sister, who volunteered her photography skills for the day and provided us with some great shots (including the ones in this post).  Check out her business, based in the beautiful Shenandoah Valley, Virginia. You can also visit her website: Saraceno Photography & Studios

“Man in a Fur-lined Coat” – about 1655-1660, Rembrandt van Rijn (photo via my camera phone, no flash, of course)

The skill of the 400+ year-old artist aside, this is primarily an earth-science blog and Rembrandt van Rijn, though having an appreciation of nature, was not a geologist, or even much of a scientist in the strict sense.  So, here’s the next best thing: an impact crater named after our Dutch friend.

Rembrandt impact crater is the sixth largest crater in our solar system.  Reaching over 440 miles in diameter, it resides on Mercury along with Caloris (an even larger crater).  That’s over twice the size of the largest known impact crater on Earth (Vredefort, South Africa).  The crater is surrounded by blocky impact deposits, but also contains relatively smooth plains within, which are interpreted as being volcanic in origin (lava flows, most likely).

Rembrandt Crater (photo via NASA’s MESSENGER spacecraft; August 7, 2011)

I’d love to include much more on the geology of Rembrandt crater but, as we know, it is Mother’s Day and I must be going.  Happy Mother’s Day to all mothers: past, present, and future!

This has always sounded like a great idea to me and yet, somehow, I haven’t managed to throw in a submission.  No more!

My Geological Pilgrimage

This month, Accretionary Wedge #45 is being hosted by Denise at Life as a Geologist, who asked us to share our ideas for a geological pilgrimage of our own.  It would be some place we feel the need to visit at least once in our lifetime.  As she specifies – “a single place, which is “geologically” unique,  relatively remote, and requires some difficulty to get to.”

I’ve been to some really neat geological places, though mostly in national parks, which aren’t too difficult to get to (most of the time).  And I know there are more places than I can count that I have on my bucket list of “amazing must-see geology”.  However, for this, I wanted something truly unique.

After thinking for all of a few seconds, I remembered reading about Nyiragongo, a volcano in the Democratic Republic of  the Congo which holds in its crater one of only four persistent lava lakes in the world.  Now, Nyiragongo was covered by National Geographic  last year and, making assumptions, this must be one of the more spectacular out of the five.  Sure, I could visit one of the other three, like Erta Ale (Ethiopia), Mount Erebus (Antarctica), or Kilauea (Hawaii), but based on the stunning photography I’ve seen of Nyiragongo, I’ve been captivated.  Besides, I have to pick just one, right?  A trip to the others might be in order as a supplement to this pilgrimage.

Nyiragongo’s Lava Lake (Photograph by Carsten Peter)

Oh!  That’s right, this is a geoblog!  So, I should introduce some interesting geology to the mix.  Well, I suppose it’s obvious that we’re looking at a volcano (or four).  We all know – to one extent or another – that a volcano occurs when molten rock (magma) reaches the surface and ‘erupts’ as lava.  A lava lake, then is simply lava that hasn’t left the crater of the volcano.  This actually happens often with mafic, non-explosive eruptions.  Why is Nyiragongo special?  Because not so common is a persistent lava lake, such as the one in Nyiragongo’s crater.  In other words, the lava here remains molten for an extremely long period of time…at least on the order of decades, but theoretically could be thousands or tens of thousands of years.

Looking into Nyiragongo’s Crater (Photograph by Carsten Peter)

What would cause a persistent lava lake?  The best solution is that the lava actually does cool to solid rock, building the crater while new lava is slowly being fed into the crater from below, perpetually maintaining the glowing lake of molten rock.  This process is very rare, and the fact that we know of only four persistent lava lakes in the world and around 1,500 active volcanoes, goes to show just how rare.

Close-up of the lava lake. As lava is exposed to the air, it begins to cool into solid plates, which float on the lakes surface. (Photograph by Carsten Peter)

What has also had me interested is Nyiragongo’s alkali-rich lava.  This chemical composition is theorized to be what makes its lava flows so “runny”…some moving up to 60 miles per hour.  Runny lava makes sense, since the silica content is so low, and mafic lavas are known to be more fluid.  My question, though, is how the slopes of Nyiragongo are so steep (nearly 50 degrees near the top) by comparison to most mafic volcanoes, which have a more gentle, shield shape because of the fluidity of their lava flows.  I’m obviously not a volcanologist, and haven’t done too much research into this (believe me, if and when I go on this trip, I’ll be doing quite a bit), so if anyone has an explanation, simple or not, I always love to learn!

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p.s. – Because I’ve never been to Nyiragongo to take my own photos, I’ve included some by Carsten Peter (National Geographic), for which I was given permission to use in a previous post.

Reblogged from lithics:

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Earlier I posted an info bulletin about this morning’s Banda Aceh earthquake.  Rather than muddle it with more and more stuff, I thought it might be better to include this update as a separate post, as it is more of a discussion than a news piece in any case.

The truth is that this earthquake is properly strange.

The part of the Indian Ocean in which this earthquake occurred has two very different types of geologic structure very close to each other; there is the Ninetyeast ridge – a volcanically produced range,  and a destructive margin subducting the Indian plate eastwards under the Pacific margin.

Read more… 885 more words

Seeing that I'm in the middle of some extensive lab tests, and am preparing to present my research (thus far) next week, I thought this would be the perfect opportunity to test the "reblog" feature on Wordpress which allows hosted blogs to easily share another blogger's work. I'm not sure if I like the feature, yet, but it serves as a great way to showcase some fine work by others...especially when I don't have the time to put in to writing, myself! Pete Rowley, on his blog "Lithics", wrote a couple great articles on today's Magnitude 8.6 earthquake in Indonesia.  Here is his second article on the quake and, please, visit his site to see the first article as well as plenty of other good reads!

Students attending a REQUIRED course for their earth science degree. - Photo courtesy www.BeaGeo.com

In my opinion, this site should be referenced in every intro earth science course from grade school through college intro courses.  Of course, I am a little biased.  Still, BeaGeo is a simple site that really shows off the many faces of earth science and how we, as geoscientists, can make a difference while doing something we enjoy.

Here is the video that BeaGeo has on their home page.  If you ever again run across someone that asks “What the heck can you do with a degree in Geology!?“, you should send them here first.  The video (as with the website) not only explains what you can do as a geoscientist, but why you should become one!

p.s. – Way to go UT Austin Jackson School of Geosciences for putting this together!

Thanks for stopping by (numerous times) and please continue to share this site with your friends, family, and random passers-by!

Diavik Diamond Mine

How do you create an open pit mine in the middle of a lake? I came across this image of Diavik Diamond Mine while perusing the internet and couldn’t help but do some brief research to answer this question.  My first thoughts were of earthen dikes and coffer dams, eventually building up the surfaces on which your operations will take place.  A less artistic version of the Dubai islands, yet more fantastic in the sense that there exists a giant hole in the center which descends hundreds of meters below the surface of the water.

The location of the mine was chosen after the discovery of three kimberlite pipes in the Yukon Territory of Canada (a region well known for these formations).  Kimberlite is a type of rock thought to be formed at great depth as part of a volcanic “feeder pipe”, essentially a conduit for magma to reach the surface.  Only, in the case of kimberlite, the magma cooled at depth under intense pressures.  Pressures high enough to create diamonds from the carbon within the system.  In this case, the kimberlite pipes are approximately 55 million years old and have intruded 2.7 billion year old, precambrian granites and metamorphic rocks.

Computer model showing Diavik open pits, proposed underground operations, and kimberlite ore bodies (red has been mined) - image via Diavik Fact Book

So how did mining begin?  As it turns out, I did miss an obvious starting point: a pre-existing island.  However, I wasn’t too far off!  The kimberlite pipes were located mostly offshore.  In order to get to them, special rockfill dikes were constructed in as much as 32 meters (105 feet) of water.  Each dike was constructed in a  sort of loop, enclosing the area above the kimberlite pipes which would eventually become the open-pit mine.  Grout curtains were installed along their base to prevent the flow of water beneath the dikes and into the enclosed area.  The first and largest dike used approximately 6 million tons of rock and was 3.9 km (2.4 miles) long.  Following construction, the enclosed areas were drained and surface mining could begin.

Dikes (A154 and A418) completed to allow open pit mining

What makes this mine even more interesting, at least to me, is that it’s nearly inaccessible.  Due to it’s remote location 300 km Northeast of Yellowknife, in the Yukon Territory of Canada, there aren’t too many roads.  On top of that, there’s nothing between the island and shore but water, unless you count the ice during the winter season…which is, as it so happens, regularly used as the diamond mine’s bridge.  Luckily, winter is not the only time product can be sent out, as the island is large enough to support an airport capable of supporting 747 jets.

Winter at Diavik Diamond Mine

Diavik’s surface mining days are now over, as it has transitioned to the even more complicated method of underground mining.  However, the extraordinary manner in which they first developed the mine, and the sight of it today, leave it high on my list of awsome achievements.

Newberry Volcano Caldera (Image with permission under creative commons, by Craig Elliot, Flickr user Tjflex2)

How is a volcano going to create electricity, you ask?  By pumping 24 million gallons of water deep into its side and capturing the hot water and steam generated, whereupon it will be sent through turbines at the surface to create electrical power.  This process is commonly known as geothermal energy, a renewable resource which developers hope – by adding this volcano element – will be made economically competitive with the cheap (and booming) natural gas industry.

The companies conducting the study will be pumping 24 million gallons of water over 10,000 feet below the surface on the side of the volcano.  Here, the cold water injected into the ground can be heated by the hot rock which, in turn, is heated by an underlying magma chamber (only 2-5 km deep).  When this water is heated, the steam is recovered to produce electricity (as explained above).

In order to efficiently heat the water, you can’t just drill a hole straight down and pump water into the ground.  This is where a process called hydroshearing comes in.  Hydroshearing is a technique in which water is injected into the boring under high pressure in order to induce and enhance fractures within the rock.  Once these fractures are in place, the cold water is injected into a newly created “reservoir” composed of this fracture network within the hot rocks.  Now, hot water and steam can quickly and easily be recovered.

Does this process sound familiar?  It should: it’s nearly identical to hydraulic fracturing.  You say po-ta-to, I say po-tah-to.  The name change is (in my opinion) a political thing.  There’s too much bad press floating around the term “fracking”, so they change the name to “shearing” and it’s automatically more environmentally friendly.  To be clear, hydroshearing is safer for the environment. The big difference here is that hydrofracking injects a large number of chemicals into the ground and hydroshearing doesn’t.

If you’re one of those worried about earthquakes induced by hydraulic fracturing, well then you should feel free to worry about these geothermal projects, too.  However, you can read a previous post on hydrofracking to hear my stance on that issue.

In the end, it seems odd to me that nobody thought of this before.  The exploitation of geothermal energy has been around for over a century, why wouldn’t we go to a location where a heat source exists much closer to the surface, thereby making it easier and cheaper to utilize.  Regardless, it seems the government and private sectors are interested in the project, investing over $40 million.    I’m looking forward to seeing the results!

I know some of you who read this live in this region of the country and therefore will be much more directly affected by this than myself.  What are your thoughts/concerns?

Thanks to my colleague, Jeff, for giving me a little inspiration for a new post by leaving this article on my desk this morning!  Please take the time to read it through a get some more details on the geothermal project at Newberry Volcano.

Today, Google has tipped its hat to geologists everywhere by dedicating its Google Doodle to Nicolas Steno on his 374th birthday.

Steno was one of the world’s earliest geologists and, by many accounts, very likely the first.  He was one of the first to theorize (correctly) that fossils may not have been naturally forming inclusions in rock, but remains of prehistoric animals.  Steno also helped to develop stratigraphic relationships, Original Horizontality and Superposition, which are included today as two of the six Fundamental Principles of Geology.

Today’s Doodle commemorates these achievements by forming the logo using horizontal rock layers representing different periods of geologic time (oldest on bottom, of course).  The layers of rock are also full of fossils to represent Steno’s accomplishments in paleontology.

Happy 374th Birthday Nicolas!  And thanks, Google, for honoring the father of geology!