More rocks: Erosion.

Here they are, trying to erode rocks with water. It is a good thing sandstone erodes with water easily, otherwise the experiment wouldn’t have been as fun.

We continued our rock themed week with a lesson on erosion.

First we had to do some more “geologist work.” We still had some rocks to find in our rock dig, so Nicholas sat down at the table and went rock hunting in the rock. He found 2 more before he decided he was done for the day. I didn’t realize, when I got it, that the rock dig would occupy so many hours, but it was a really good investment. It is quite the project and he really likes it. If he was older, I would have him practice making a journal and recording his finds, like an archaeologist records their finds.

The we did our word practices for the day: mineral, erosion, wind, weather, rain, and water.

We did some reading in our favorite rock book about what causes erosion. The causes of erosion are weather (wind, rain, find dust rubbing), people, rubbing, and machines. We read about how weather can cause rocks to change their shape and break down.

In order to demonstrate this we headed outside. We took the big chunks of sandstone from the rock dig and used them as our rocks to erode.

First we wanted to see how wind eroded rocks. We blew on them, fanned them, and flew them through the air. Nothing made a noticeable change in the rock. So I explained how wind erosion works very slowly over time.

Second, we tried making some rubbing erosion. We rubbed the sandstone on various surfaces (concrete, the tree bark, the fence) and watched how they changed. Nicholas was also fascinated that sandstone erodes into sand particles.

Third, we did some water erosion. We turned on the hose and held it at different heights against the rocks to watch them change. We saw how the rocks “melted” into sand. It was really cool to see how he would race against his previous rock’s demolition time to see how fast he could “erode the rock into sand with the hose.”

Finally, we used our feet to show how people walking on rocks can erode them too. It turned into a stomping match between him and his sister. I do think the point got across.

When we went back inside, we read the rock book about the rock cycle and Nicholas had to guess what happens to the small rocks and sand after the erode. He correctly said that the rock cycle says they will turn back into rocks sometime. That’s all I expect from him.

It was fun to watch him erode the rocks. He was quite ingenious with finding surfaces to try and rub them on.

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