Monday, May 16, 2016

Igneous Rock

We have done a lot with rocks and the rock cycle before, so we didn't go all-out with it this time. There are tons of fun activities to do, though—igneous fudge, the chocolate rock cycle, and geologic brownie sundaes, to name a few. :) This one is similar to the "igneous sugar" activity we've done before, and demonstrates how crystal formation is aided by greater periods of time and warmer temperatures.

Sugar that cools very quickly forms very small crystals, or no crystals at all. To demonstrate, you melt sugar with a little water in a pan until it is just golden brown. Then pour the molten sugar in a very thin layer onto a pan you've had in the freezer. The sugar will cool almost immediately into this smooth, glassy substance, similar to the way obsidian or volcanic glass forms.
It's really quite beautiful.
On the other hand, if you make a supersaturated sugar solution that will cool very slowly (put it in a tall jar or glass, with a lid if possible), the crystals will have time to grow in a much larger and more definite form.
Like this. Ours took days and days to cool, so be patient! :)

This was a demonstration of how different types of magma flow at different speeds. The viscosity of magma affects what types of volcanoes will form in a particular location. We talked about this more during our volcano unit.

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