More regelation

This fall we had 5 students from a local high school come one day a week for lab activities. In addition to a long term regelation project, each week there were lab exercises. These exercises
ranged from cheese squeezing, to phase equilibria, to earthquake triangulation. We also gave another go at the classic regelation experiment. I tried this with students in the summer and the ice pieces were too small and some wire was too thin. This time I think we got the right combination.

The idea is that the pressure is great enough just below the wire that it pressure melts the ice but then right above the wire the pressure is low and it refreezes, thereby trapping the wire inside the ice as it makes its way down. Theoretically, the thermal conductivity of the wire is important for the process.

Success!

The students then applied this idea to a long term project in which ice was placed on top of beads and a weight was placed on top. Each week they used a different size or different type of bead. In theory if the bead is embedded into the ice by viscous (solid-state) creep, then it wouldn't matter what type of metal was used. But if it occurs by regelation, then the type of metal (and therefore the thermal conductivity) is important. They had really nice results demonstrating a mix of both types of deformation depending on the conditions (particularly the size of the bead, which controls the stress). 

The work was all done in a commercial chest freezer, which isn't ideal for temperature control, since it oscillates with the freezer's duty cycle, but is good for a school project lasting all semester.

They became familiar with running experiments, taking notes, analyzing data and communication results (we had an informal poster session at the end of the term)

Rock Mechanics at AGU

This year's AGU was held in DC. It was fun to check out a new venue, but not fun getting lost trying to find everything. The convention space, which connected underground to the Marriott next door, was just cavernous. And I don't think we've all really mastered where to put ourselves.

Despite that, I did manage to make it to most everyone's posters ...

...including my own (though my shift was at 8am, so it was rough)

Allie and Jessy

I would be remiss if I didn't mention our visitors from Brown University this summer. Allie and Jessy are undergraduates in the geosciences department who wanted to gain some lab experience. They worked on measuring wave speeds in partially molten ice samples. This involved lots of time in the cold room...

Working with Mike, they put together this special baby cryostat to maintain temperature around samples. Inside the cooled cylinder sat a sample of ice + ammonia and on either side of the sample were ultrasonic transducers.

They were very careful, took excellent notes, and calculated error bars. At the end of the summer they presented their (tiny) poster at an informal poster session at Lamont.

And they did such a nice job, that we will publishing their results in an upcoming special edition of Geosciences about Interiors of Icy Ocean Worlds. Stay tuned for that and for great things to come from these young researchers!

Daning says goodbye

Last year we had a visiting grad student in our lab. Daning Zhong was working on a modeling project and helping with friction experiments in the lab.

In September she had to return to China because her 1 year visit was up. At Ted's goading, we took a walk around campus for a photo shoot. 

It was really nice having her visit. She did a great job applying the Aharonov and Scholz constitutive model of friction to high homologous temperature ice friction. Stay tuned for a Zhong et al. publication coming soon!

Open House 2018

For this year's Open House, Rock Mechanics put together a new demo to try to convey the idea of strain in a sample. The first task involved getting our hands on some polarizing film.

Then Rob and Mike put together a special box to look at a sample of PMMA in polarized light. In the back is just an old computer monitor actually and that new film was placed in front. Here it is unstressed (you can see residual strain from fabrication).

Rotated to a different position.

And stressed.

Rock Mechanics at the GRC

We got the whole team together at this year's Gordon conference. What a great group!

We even had our newest member, Seth, who hasn't started yet.

Seth won the Lamont Postdoc Fellowship and will start this spring. He's going to be working on ice-till friction but will revamp and include all kinds of new gadgets and methods, like measuring acoustic emissions and using machine learning to compare lab micro-events to real ice stream events. We're super excited to have him joining us!

New grad student Kristina, who is working with Heather, also joined the conference and killed it at her poster session.

Although we're not supposed to take pictures, I snapped a super fast one of Genevieve during her opening slide. She was one of only a couple of students asked to give a talk at the conference. She did an amazing job!!

And if you've ever been to GRC, this last picture needs no introduction. The non-vegetarian amongst us all donned our little bibs and dug in. Over all another great GRC!

Regelation or Viscous Deformation?

This summer, in addition to five other interns, we also had four students through the Climate and Life program: Camille, Jeremy, Naomi, and Jennifer. They were looking at the difference between regelation (pressure melting and recrystallization) and viscous deformation, which could be mechanisms of flow at the base of glaciers under the right conditions. Mike built a frame to go with Rob's dead weight apparatus that the students assembled. They calculated the stress for each increment of weight to be added. 

They did a great job drawing the below schematic of the set up. The frame was used to apply a dead weight to the top of the ice, which was resting on top of spheres of various size and composition. The  hypothesis was that under some conditions regelation would dominate over viscous deformation and other conditions it would not. Since any melt formed would drop down below the balls due to gravity, we would be able to tell the difference. Also, in theory, regelation should be faster with spheres of higher thermal conductivity so we thought me might be able to tell the difference that way.

They printed up their motivations, methods, and results into a nice poster. Title was all their idea, and I love it!

And they did a great describing their project to the other interns and my colleagues at an informal poster session held on the last day.

With about a half hour left before the bus, they enjoyed some competitive stress concentration and particle interaction.