The outer shell of the Earth, called the lithosphere, is broken into about a dozen major "plates." These plates are "floating" on the asthenosphere and are able to move around because of the properties of the asthenosphere. The asthenosphere is a solid, but it is very hot, allowing it to flow slowly.
We know that the asthenosphere is a solid because S waves can travel through it, but we also know that it can flow because the plates are moving about without any earthquakes at their bases and at oceanic trenches, oceanic plates actually sink into the asthenosphere.
We can make some "silly putty" (also called Flubber) that has somewhat similar properties, in that it is elastic enough to bounce, but it will also flow slowly if under any stress.
Here's one Recipe:
Borax (can be found with laundry detergents in most grocery stores)
White craft glue, such as Elmer's
Two empty plastic soda bottles with lids
In one soda bottle, add 1 cup of water and 1 tablespoon of Borax. Shake until dissolved.
In the other bottle, add 1.5 cups of water and 1.5 cups of white craft glue. Shake until mixed well.
To make putty, combine 1 part of Borax solution with 3 parts of white glue solution in a small cup. Stir with a small stick until firm and then remove the putty and knead it by hand to get a smooth texture.
Replace the Borax solution with liquid starch (can be found near the laundry detergents in grocery stores).
Proceed as above except that equal amounts of liquid starch are combined with the white glue solution.
This recipe requires a bit more mixing with the hands, and seems to be a bit more messy, but the end result is a very similar putty.
Although these substances are not considered hazardous, you should treat all chemicals with care, and wash your hands after handling them. To not taste or eat any of the materials. Keep out of reach of small children and clean up any spills. Clearly label the containers of ingredients. Do not pour any material containing white glue down the sink. Do not allow any putty to remain on clothing, upholstery, wood surfaces, or carpet, since they may stain or damage them.
How it works (From a handout provided at the 2006 da Vinci Days celebration in Corvallis, OR.)
White glue contains polymer molecules -- long chains of covalent-bonded atoms. These act a lot like microscopic strands of cooked spaghetti. In the liquid glue, these long molecules are not hooked together. They can slide past each other and the glue can flow, just like spaghetti will slide around on your plate and off your fork. However, if these long molecule chains become bonded together you can get two basic types of polymeric materials -- plastics and elastomers. In elastomers, the polymer molecules hook together at a few places along the strands. In elastomers, even though they are bonded, the individual molecules can still move and the result is a rubbery solid that stretches.
The Borax (a natural mineral composed of sodium, boron, oxygen, and water that is used as a cleaning agent) forms chemical bonds between the glue's polymer molecules. This hooks them together so they can't slide around as easily. It doesn't lock the strands in place (as in hard plastic) so the resulting putty can be stretched and formed into different shapes.
For more information on Silly Putty, see: sillyputty.group4.html