Which is a better analogy for the Asthenosphere?
Because S-waves are able to travel through Earth's Asthenosphere scientists infer that it is nearly solid. However, one of the fundamental concepts of plate tectonics is that this hot, weak solid flows over long periods of time (a property generally associated with liquids). For most students, the notion of a "solid flowing" is very discrepant. Given the discrepant nature of the concept, it is important that learners have an opportunity interact with concrete models of the Asthenospehere so they can add this to their own mental model of plate tectonics. In this activity students will evalaute Silly Putty and Oobleck, both of which demonstrate proprieties of both solid and liquids, as a potential concrete model for Earth's Asthenosphere.
This activity is from Project Earth Science © 1990 Horizons Research, Inc.
Students will be able to:
Silly Putty is used as a model to show how the asthenosphere is elastic when exposed to short-duration forces (like seismic waves) but plastic when exposed to long-duration forces (like the load of the Hawaiian Islands on the Pacific Plate).
Conceptual model of the relative thicknesses of the Lithosphere relative to the diameter of the Earth uses a hard-boiled egg to gain understanding about the scale of the lithospheric plates.
Video lecture on how temperature controls mechanical behavior of materials, including rocks. A Big Hunk candy bar is used as a model. The cold candy bar is brittle whereas the warm candy bar is ductile or "plastic".
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A candy bar, made almost entirely from nougat, is a useful model for connecting strain in rocks to faulting (earthquakes) and folding.
Using Silly Putty™ as an analogy, this activity extends student understanding of the deformation a rock undergoes as a result of stress, plus several factors that contribute to the behavior.