Sediments and Erosion

Somehow in all my years of studying geology, I never understood that clay and silt and sand are simply names for materials composed of different sizes of sediment! We collected samples of each type and sorted them onto a plate, and then looked at them under the microscope.

Here's what sand looked like. Cool, huh? Like teeny pebbles. Which, of course, it is!

We also looked at how weathering and erosion affects different sediments. 

You can see, as we dropped water on our "mountain," the water wore away at the slopes, and formed river channels where it "preferred" to flow. You can also see the deposition of sediment at the bottom of the "mountain."

Wind plays a part in weathering and erosion as well.

Eventually, the mountain is all worn away and the sediment has been deposited throughout the flood plain.

We looked at different sizes of sediment too. The water, obviously, had less of an effect on large "boulders" than it did on smaller sediments.

After flooding the sediments, they mixed and settled. Then we allowed the water to evaporate for a few days, and when it was gone, we had a "sedimentary rock" composed of the old sediment.

We also repeated an activity we've done before, where you put different sizes of soil/sediment into a bottle, add water, and shake it up. The sediments mix and then settle to the bottom in layers sorted roughly by size. It's cool to see it work.

More sedimentary rock activities—here.

Sprinklers and Irrigation

Of course, you know we had to spend at least a little time studying sprinklers and irrigation systems. We studied some of the irrigation methods throughout history (Egypt and the Nile, the "hanging gardens" of Babylon, etc.) and we read several sections from this book:

which, I should point out, was a great labor of love on my part, since it was very technical and had lots of pages like this in it:

But I knew the boys (especially Seb) would love it, and they did. Side benefit: I now know why our backyard sprinkler system works so poorly (guess we shouldn't have gone with the cheapest bid). Huh, if only I'd read this book a couple years ago!

We did some soil analysis (an exercise from the sprinkler book) and found that our soil here is mostly clay with a bunch of rocks in it. Not ideal, as we knew. But the topsoil we brought in is pretty good (for our herb gardens etc.); I just wish we had more of it.