Earthquakes and liquefaction

I feel like we've talked about earthquakes a billion times, but (to my children at least) it never seems to get old! :)

This time we did a liquefaction demonstration. You fill up a big container with sand, then stir in water until the sand is quite saturated. This represents your groundwater. You can also add blocks to represent buildings, for dramatic effect. :)

Then you shake your container vigorously. The sand becomes suspended in the water, and the area is temporarily liquefied. You can read more about it here.

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. 

http://video.pbs.org/video/1863101157/

Some description of what caused it in this one

http://www.youtube.com/watch?v=foxww-tMoNg

The bigger wave comes in near the 5:00 mark

http://www.youtube.com/watch?v=IAa8BmuPqh8

This one gets interesting around the 4:30 mark

http://www.youtube.com/watch?v=I-KiGboUuy4

Newscast that shows some helicopter shots

http://www.youtube.com/watch?v=J2hUwFo6Vpc

http://www.youtube.com/watch?v=X3CleAc_iQ8

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

http://www.youtube.com/watch?v=-VcWF8dIDj4

http://www.youtube.com/watch?v=WRvcBBGIWio

http://www.youtube.com/watch?v=2rAJOo_VBhk

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)

http://www.youtube.com/watch?v=TRDpTEjumdo&list=RD2rAJOo_VBhk

http://www.youtube.com/watch?v=5-zfCBCq-8I&list=RD2rAJOo_VBhk

http://www.youtube.com/watch?v=vzvZy1zY8U8&list=RD2rAJOo_VBhk

Showing the aftermath

http://www.youtube.com/watch?v=MyTTrj4wKMU&list=RD2rAJOo_VBhk

Making a seismograph

I'm not totally sure I'm clear about the difference between a seismograph and a seismometer---I think seismograph is the older term, referring to a machine that actually outputs the data on paper (a seismogram). Now, they're usually called seismometers because they record the data digitally. If I've got that right, that would make our machine a seismograph. This was a fun project suggested in one of the books we read. It's easy to make---you just poke a hole in a paper cup so that a marker tip will fit through, like this:

You suspend the cup and marker from a string inside a box. Thread a long strip of paper through slits on either side of the box, and then gently shake the box as another person pulls the paper through.

Here is the seismogram our seismograph made! I think we recorded some large earthquakes. :)

Natural History Museum

Sebby is SO HAPPY about this huge quartz crystal!

We went to the Natural History museum especially for their "special exhibit" on Natural Disasters, since we were about to start our Natural Disasters Unit. I'll try not to dwell with too much bitterness on the fact that the museum closed a half-hour before I thought they closed, so we got kicked out of the exhibit just as we were starting it by a zealous docent (although, as I pointed out to her, there were still 5 minutes left---"But we need everyone OUT by closing time," she replied implacably). As I said to Sam later, I've been kicked out of museums at closing time all over the world, so you think I'd be used to it by now, but I still get annoyed by that smug, not-my-problem attitude the docents always show as they sweep you toward the exit. It WAS my own fault for mis-remembering the closing time, as I thought I'd allotted plenty of time for the last exhibit. Still . . . what if a restaurant served you a lovely meal, then whisked it away mid-bite as the clock struck closing time? It was maddening.

Luckily (or not, I guess), the natural disasters exhibit wasn't that great anyway, as we saw while we were herded madly along through it to the exit. It was only a couple rooms, and had just a few rather basic "interactive" areas ("Feel this pumice!" "This slinky makes P-waves!") along with the usual tired Climate Change canards. So, no great loss.

The rest of the museum, which I had wisely (ahem) allotted most of our afternoon to, was great. We especially loved the minerals section, which had a great variety of specimens, many from Utah.

Erosion Table, always fun

Daisy making waves on the seismometer

Earthquake simulator (this "building" has cross-bracing and a tuned-mass damper on top to help stabilize it)

Beautiful topaz! We wish we'd found this!

Outside the museum

Skyscrapers and Jello Earthquakes

This was a fun activity to test different types of structures and how they stand up to earthquakes and liquefaction. We got the idea here. This would be a good thing to do in a Natural Disasters Unit, too!

We built structures using mini-marshmallows and toothpicks, trying to keep in mind the architectural principles we'd learned about what makes structures stronger (like wide foundations, triangle and truss-reinforced walls, and so forth).

Then we put our structures onto our pan of jello and shook them up to see how they withstood the earthquake! Fun.

The taller structures were definitely harder to keep stable!

There was one among us who did more eating than building, unfortunately.