Rocking Along

Science Class this week was all about rocks. This was a case where I waaaay overestimated my time. I started out talking about the three main kinds of rock: sedimentary, metamorphic and igneous.

As it happens, on one of our many forays hunting fossils near Calvert Cliffs, we happened upon a recent chunk of fallen cliff that was loaded with the impression of fossil shells. The most interesting thing about it was that the hunk-o-cliff was not actually rock, but compressed sediment. Clearly it was turning into rock, but it could be easily crumpled with your hand.

That's the tan chunk in the middle.

On another trip, we found a chunk-o-something that looks like shells stuck in cement. Except, it's not cement! It's a harder layer of sedimentary rock "under construction!" Interestingly, these shells do not appear to be fossilized, whereas the impressions in the softer "compressed sediment" are completely dissolved away.



We actually have a lot of sedimentary rock in our collection - almost all fossils are in sedimentary rock. Most of the rest of the collection is igneous Oooooh! Pretty crystals!).



This is where I kind of lost the class. I had radically underestimated how long the kids would want to look at the rocks.


This is one of our four containers for small rocks...


Basically, I should have turned them loose with magnifying glasses and the rock collection and left them for half an hour, and then spent the next class explaining what they had seen.

What I actually did, was move on to the rock cycle. This was a great idea I lifted from the internet somewhere..

The kids each choose a crayon. Working in teams of 2 younger kids and one older Zoomlian, the Zoomlian shaved the crayons with a sharp knife onto a sheet of double thick foil.

When they had enough shavings, the kids pinched them together. The shavings stuck together loosely, and you could see the individual shavings, kind of like sedimentary rock.

We folded up the foil and the kids hammered on it. This pressure caused the shavings to really stick together and merge a little, kind of like metamorphic rock.

Then we heated the foil packets a little on the stove (you could also do it over a candle) and then cooled them in the freezer. Of course, the shavings melted together and formed a solid, homogeneous whole like igneous rock!

UPDATE: I found the experiment on this video:


And then we were ten minutes over time....

So, next week we'll set up a ton of crystallization experiments and make our own "pumice."