Rock mechanics on TV!

Today I did an interview for a public television program called SciTechNow. I was contacted because of my affiliation with Science Cheerleaders and because the head of that organization was not available for the interview. I talked mostly about that organization and SciStarter, an online citizen science group.  But it also gave me an opportunity to talk a little bit about the rock mechanics lab and about why I got into science.
This morning after dropping off the baby I headed down to 66th and Broadway to the Tisch WNET studios at Lincoln Center. First stop was up to the green room to get my hair and make-up done.

Then I was brought down to the waiting room couch, right there on the corner of Broadway. I was the last in a series of eight speakers.

When it was my turn, I was fitted with a microphone and the make-up artist touched me up, shellacking that stray hair back out of my eyes.

Hari was really nice and easy to chat with. He asked me several questions about Science Cheerleaders and about Sci Starter. I think I was a little like a deer in the headlights on my first question (I sure hope they do some editing) but after I got warmed up, it went pretty well. 

After the interview I recorded two segments for their  "Ask a Scientist" feature. This is where scientists try to provide an easy to understand answer to a science question in one minute or less. I answered "What is tidal heating?" and "How do we know what's inside the earth?"

I don't remember saying much about subduction zones, but apparently it is physically impossible for a geologist to give an interview and not make this hand gesture.

Afterward Hari took a photo with me. Pretty fun way to spend the morning, but I'm happy to be back in my grubby clothes and in the lab getting dirty again.

Reaction driven cracking with Sarah

There's a new experimental project occurring in the rock mechanics lab right now. Sarah Lambart, who is usually over in the petrology labs, is conducting some preliminary desktop studies of reaction-driven cracking that may ultimately be performed in the triax. Below, her sample material sits within a steel cylindrical die and she is using weightlifting equipment to determine if the reaction rate depends on stress (it does!)

 Another test determines the rate of the reaction with warm basic fluid (but without stress).

Strain gages attached to a copper jacket around the sample should capture volume expansion and cracking caused by a reaction of water and calcium oxide. 

 Transducers attached to the sample will monitor cracking. Sarah tests one out and observes the signal.

Cryostat stage 1

Our newest member of the lab is Mike Nielson, who will be doing his senior thesis project working on ice. Specifically he will be troubleshooting and calibrating the cryostat and testing standard ice samples for grain growth or degradation after thermal pulses.  On his first day he already made a big contribution to the ice project. Rather than the duct taped styrofoam contraption that I was envisioning for insulation, he suggested we use expanding foam to get a perfect fit to the cryostat dimensions. 

At home he built a wooden box lined with wax paper. We placed the cryostat inside the box and released two full cans of Great Stuff expanding foam in the area around it. A wooden bar over the top covered the ball bearing sleeve that the piston goes into. The bar also held down the cryostat when the foam expanded.

And did it ever expand!  He taped the sides so that the foam would "grow" toward the center. We actually worried that it wouldn't fully cover the top of the cryostat. Clearly we didn't have to worry. It covered completely and pushed its way out. After it fully dried, he easily removed it from the box,  cut the top off, and cut the insulation into two halves. Eventually we will use duct tape or velcro to make a seam that will hold the two parts together.

He cut a hole in the side to allow for the peltier cooling device and heat sink that I will discuss in more detail later. Shown here is a fan sink. In the next blog installment I will show the circulating liquid sink that we are now using instead. Stay tuned!

Open House 2014

On October 11th, Lamont held its annual Open House, during which our doors were open to the public. Most labs or research group put together a booth or presentation to highlight what they do as well as entertain/educate our guests. Despite the rain, we had a huge turn out this year. In the Rock Mechanics lab we had a constant stream of excited kids and adults come enjoy our presentation called "Bending, Sliding, Cracking, Squeezing Rocks". 

 A slider block pulled along by a motor demonstrated stick-slip events that were monitored by a transducer and displayed in real time on a computer screen.

Heather demonstrated reaction driven cracking with a piece of calcium oxide submerged in water.

Hannah discussed similar cracking occurring over longer time scales in expanding mortar within cored sandstone...

…and in naturally occurring peridotite samples.

 I used a rock that Ted had rigged up with strain gages to demonstrate how to squeeze rocks and watch the dial on the analog meter move. 

Visitor in the cold room

Early this month Tess Caswell a graduate student from Brown University came to visit us and image ice samples with our brand new, cold room-designated microscope and microtome. She risked strange stares from fellow passengers as she lugged a dewar of liquid nitrogen onto the Amtrak train, through Grand Central, and out to Queens via subway.

In the outer refrigerated room at Lamont, she developed a protocol for breaking off bits of sample and affixing them to thin section slides. She used tweezers and razor blades and worked on top of a metal platform that sat in a small cooler filled with liquid nitrogen

Then she braved the cold (-29degC!!) to spend time microtoming the samples. She first tried transmitted light mode on the microscope and thus needed to shave the samples until they were very thin. Later she tried reflected light and was able to keep the samples relatively thick.

Ultimately the thick samples in reflected light proved to be the best for imaging grain and sub-grain boundaries in her previously deformed samples. Great images, Tess!

She plans to come out again soon and try to also determine orientation of the grains.

Field trip to Italy

by Hannah Rabinowitz

This summer, Heather and I had the opportunity to go to the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome.  In addition to spending a lot of time making our way through the gelaterias of Rome, we were able to run a couple of series of experiments on two different deformation apparatuses in the rock mechanics lab there.

Taste-testing gelato at a gelateria recommended by Kevin Uno

The apparatuses we used this summer in Rome.  SHIVA is on the left and BRAVA on the right.

One set of these experiments was conducted with Giulio di Toro and Elena Spagnuolo on the Slow to HIgh Velocity Apparatus (SHIVA).  SHIVA is a high velocity rotary shear apparatus that can slide either intact rocks or gouge layers at high velocity and high normal stress.  This is actually the apparatus that first got me interested in rock mechanics research.  After seeing a video of one of the first SHIVA tests in which solid rock samples were sheared to form pseudotachylite (frictional melt) during a class in undergrad, I went straight to my professor’s office to ask to work in his lab.  Though I did experiments on a different deformation apparatus for my undergraduate research (a Griggs rig), I was lucky enough to get to go use SHIVA with my undergrad advisor the summer before starting at Lamont.  So in a way, I’ll always feel I owe more to this apparatus than just the cool results that it can give us!  But really, who could watch this video and not fall in love with rock mechanics?

In our experiments this summer on SHIVA, we sheared gouge at high velocity to induce frictional heating.  The goal of these experiments is to expand the kinetics of biomarker thermal maturity to shorter timescales than is achievable in our hydrous pyrolysis apparatus at Lamont.  We also conducted slow velocity shearing experiments to test the impact of shear without significant heating on biomarker thermal maturity.  This will be important when using biomarker thermal maturity to estimate temperature rise on faults.  If shear strain can have similar effects to heating on biomarker maturity, then these effects must both be considered when we try to determine the size of the earthquake that could have produced a biomarker anomaly.  However, if the shear strain does not impact biomarker maturity significantly, then we can be more confident that a signal in the biomarker record is recording an earthquake. 

Heather prepping a sample of Woodford Shale to run on SHIVA.

Our second set of experiments were conducted with Cristiano Collettini and Brett Carpenter on the Brittle Rock deformAtion Versatile Apparatus (BRAVA), a new biaxial deformation apparatus with which we could control pore fluid pressure as well as confining pressure.  In this set of experiments, we deformed samples of sediments that are being fed into subduction zones.  We chose samples from two subduction zones in order to have a range of different carbonate content in our experiments and address the question of how compositional heterogeneity can affect the different seismic character of subduction zones.

We were fortunate to finish our planned experiments with plenty of time to spare.  Because of this, we were able to go out into the field and collect samples from a couple of faults in the Apennines.  Specifically we got to sample the Monte Maggio (a normal fault) and Spoleto (a thrust fault).  These faults were completely spectacular and we were able to drill samples from both of the fault surfaces as well as several off fault samples to use for the biomarker paleoseismic indicator project.

Drill holes from our samples on the razor sharp contact between the footwall Scaglia group red limestones and the hanging wall cataclasites at the Spoleto fault.

Heather and Brett sampling the Monte Maggio fault.  Our hosts were amused by our commitment to wearing purple gloves in the field.

Heather and I in front of the Monte Maggio slip surface.