Gelatin and High Speed Video

You may have seen something like this before - using polarized light to show how a material deforms under stress. I hadn't heard anyone using this technique on gelatin before, so I just had to try it out myself. What a lovely effect. There was som über geekery to be had when we noticed you could easily produce interference patterns. I'll be providing you some more details for tomorrow's demo, but here's a peek into what's going on in the dirt lab:


For all of you strain junkies out there: I'm thinking we are looking at longitudinal strain effects at first - these spread out to a maximum distance quickly and are then overtaken by the transverse surface waves as they radiate outward. Lockwood (Outside the Interzone) mentioned that he had disabled embedded video to reduce computer issues he was having, so here's a still from one of the experiments - this way even those without video capabilities can see what's going on.

Suggestion-based high speed

Earlier, I had asked for some suggestions about geologic concepts that would benefit from some high speed. Ron Schott suggested rock failure modes. While I'm not equipped to really fracture rocks properly, I can show something similar by showing what "soil" does under compression. Soils, like rocks, fail by "shearing" - even though a compressive force is applied to the plug of soil, it fails and squishes while pieces slip past each other.



On the subject of rock mechanical analogs, the snow on the student center roof has developed some lovely overturned and sheared folds:







Rock behaves differently on the continental scale than it does when we hold them in our hands. Hold a rock in your hand, smack it with a hammer and it will probably break into many pieces (brittle deformation). But pile a few more kilometers of rock on top, push on it slowly through tectonics so that the stress is applied over a large area, and watch the rock twist and bend wildly before finally breaking.