Re: Volcanoes & Earthquakes

From: Jo Schaper (joschapern4ospam_at_2socketdot.no5net)
Date: 02/20/05 

Date: Sun, 20 Feb 2005 09:43:00 -0600

Stuart wrote:

> Charani wrote:
>
>>My 9 year old dau was asking how earthquakes happen, what causes them
>>and the same for volcanoes. She also wanted to know why we didn't
>
> get
>
>>volcanoes in the UK. She was surprised that we do get earth tremors
>>here.
>
>
> You can get tremors almost anywhere.
>
>
>>Could someone give her a fairly simple explanation without too much
>>technical detail please??
>>
>>TIA
>
>
> The Earth's surface is broken up a like a puzzle. Some pieces are big,
> like the size of North America, and others are much smaller like the
> size of Texas. These pieces, which scientists call plates, are
> continually moving. Each of these plates have rough boundaries with
> other plates and these boundaries are called "faults". As the plates
> move earthquakes occur on the faults. 99% of all earthquakes occur on
> the plate boundaries or faults.
>
>
> Stuart
>

My grandma had a little 15 piece sliding puzzle in a frame. There was
room for 16 squares on a 4x4 grid. The object was to get the numbers
lined up in sequential order from upper left to lower right. To do this,
there is a lot of shifting and bumping going on. You hold the puzzle
with your fingers underneath--your fingers are the heat and pressure
within the earth. Your fingers are solid, but they have some limited
movement.

Although the Earth does not have a lot of 'empty space' on the surface,
plate tectonics works a lot like that little puzzle. As the plates shift
around, the edges catch and snag. Sometimes they bend up, sometimes they
bend down. If you pushed them together very very hard, friction would
increase between the edges, and they would melt. The melt would run
beneath the adjacent puzzle piece, push it up, and if the second plate
were heated and thinned, eventually you could have a volcano.

Earthquakes are the noise you hear as a result of the pieces clicking
together. Assume you have the first row assembled BLANK-1-2-3.
Sometimes, if you press on the open edge of the 1 tile, the force can
tranmit over pieces 1 and 2 and cause the space between the 2 and 3 to
buckle (either up or down). This is the cause of earthquakes and tremors
not along a continental edge. Sometimes you have forces pushing from
three directions at once. This may cause a turkey foot shaped crack
called a rift. Sometimes these pressures bend the frame, up or down
warping the pieces. Sometimes your little brother puts a match under
piece 8, the plastic melts and bubbles up, forming a domed 'hotspot'
such as Yellowstone--volcanoes, earthquakes and geysers which aren't
along the edge of the puzzle.

You can do a lot of basic geology with this little puzzle. One of these
puzzles is online at >
http://www.arcademachine.com/go/java/preview/A0051.tam

or just put '15 Piece Puzzle' into a search engine.

Jo

Relevant Pages

  • Re: Volcanoes & Earthquakes
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  • Earthquakes - predicting and stopping the next big one
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