Rocks flow when conditions are right. At the introductory level, many students exhibit an initial tendency to resist the idea of something they "know" is hard and brittle acting in any other way. Faulting, they get. Shear zones... not so much. I find analogies useful in communicating the behavior of rocks at depth, like mylonites. Often I invoke wax, which can be cold & brittle, hot & ductile, or molten.

But I reckon it's instructive to have other clear indications of ductile flow: everyday objects that have flowed under stress.

Today, I offer the first in what I hope will eventually build into a longer series: everyday examples of ductile flow. We begin with a cassette tape left in a hot car (viewed through the back window, which is why the photo is so lousy):

Even the relative moderate stress of leaning on the seat cushion was sufficient to bend this cassette tape, provided it had attained the right temperature (which it's easy to do in the Virginia summer time in a closed automobile).

Anyone else have examples of everyday examples of ductile flow?

Labels: analogies, structure, teaching