Country: United States
Date: October 16, 2005
Does the Earth contain a certain amount of magma or does
it produce magma?
If so how does it generate the magma?
Our theory is
that the Earth recycles itself. (This is a Third Grade Theory)
Try this approach by way of explanation:
Show your students a ball of Silly Putty. Show that it bounces (is a
solid). Then show that by pressing on it, the silly putty flows - becomes
viscous, liquid-like. Extend that thought to metals and other solids at
very high pressure. Explain that the gravity of the Earth (which pulls
everything inward) would produce a very high pressure and cause even
metals to become molten, liquid-like. (You will probably also need to
generate another visual on why the Earth's core is hot - but that will
take more concepts than is available in this little show and tell.)
Greg (Roberto Gregorius)
You are asking great questions! I hope that you are enjoying studying
Earth. It has always been one of my favorite subjects! I will try to answer
your questions without getting too technical. Scientists have not figured
all of it out yet, but we have some good ideas of how we think it works.
Some of the things you might want to look for to learn more are: rock cycle,
igneous rock, magma, lava, plate tectonics, spreading zones, subduction
zones, hot spot volcanism, mantle and crust.
The Earth produces magma under certain conditions. The Earth is a great big
rock recycler. If you are familiar with the rock cycle, you can see that any
rock can be melted to make magma. There are a few places where this usually
happens. One area is at a place where new crust is being made, at places
called spreading zones. Here, magma leaves the interior of the Earth (but
not too far down---magma does not come from the core as some people
think---it comes from the bottom of the crust and the mantle), and comes to
the surface. Another place is at areas called hot spots. This is how Hawaii
was and is still being formed. A third place that magma comes out is at
areas called subduction zones. These are places where one Earth plate is
moving under another Earth plate. The plate goes very deep and there is a
lot of pressure, so the rock melts into magma. Then it rises and emerges as
lava through a volcano or a vent.
I hope this helps explain some of what goes on. The Earth does recycle rocks
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