Showing posts with label wind. Show all posts
Showing posts with label wind. Show all posts

Tuesday, May 24, 2016

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.

Wednesday, December 11, 2013

Tsunamis (and other waves)

We quite enjoyed learning about tsunamis! Because of recent tsunamis in Japan and Thailand, there is a LOT of video footage of these huge waves. And as awful and terrifying as these events were/would be to experience, it is undeniably fascinating to see the pure power such enormous waves possess! Sam previewed the videos for us to make sure there was nothing too disturbing for the children to see. (In fact, if anything, they were a little TOO enthusiastic about the videos---I tried to impress upon them that real people are affected by these disasters, but it's hard to overlook the amazingness of those waves!) I said I hoped no one would have nightmares, and Malachi said it was going to give him goodmares. Hmm.

We did an activity to compare the origins of waves---regular waves, which are caused by wind, and tsunamis, caused by earthquakes. We got the idea for the tsunami-maker from this book.

You can find more resources on waves here.

To make your tsunami model, you cut out the bottoms of two nested foil pans (you could use just one, but two is more stable). Then cover the hole with duct tape. I can't remember what happened here---maybe we ran out of duct tape? You can see we used packing tape for the bottom side and duct tape for the top, so ours wasn't totally watertight.
Fill the pan with water, and proceed to experiment! First we set our pan down and blew on it with straws, making wind waves. We got some pretty big ones.


Then, we held the pan up and hit the flexible bottom part (the tape) from underneath to create tsunamis. You can really see a difference in the size and type of wave created by a disturbance under the water (an earthquake) rather than a disturbance above the water (wind). The earthquake waves are much taller and stronger because of the sheer amount of water they displace! We were inside the house (with towels) so I didn't allow the tsunamis to get TOO enormous, but I imagine you could do even more with this activity outside on a warm day! :)

Here are some of the tsunami videos we watched:

This video is a longer one that shows some of the footage from these other links. It's an entire program so it discusses how tsunamis form, etc. 

Some description of what caused it in this one

The bigger wave comes in near the 5:00 mark

This one gets interesting around the 4:30 mark

Newscast that shows some helicopter shots


This is interesting because it shows what the waves look like before they get to land.



This one really shows the power of the water, but it does show some little kids screaming and crying about halfway through (they're safe, just scared)



Showing the aftermath

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