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Under Your Feet - magma, asthenosphere, lithosphere, mantle
Under Your Feet
magma, asthenosphere, lithosphere, mantle
The Earth System Unit
What if the Earth were a chocolate candy? On the outside, you would have a clear wrapper. That is the
atmosphere, or the air we breathe. Yes, it really is that thin. Unwrap it so you are just holding the Earth
itself. It's a swirl of brown and blue. The harder shell of the chocolate is the Earth's crust. That's the solid
stuff we stand on. What lies underneath there? There's only one way to find out. Take a bite. I hope you
like hot stuff.
Crunch. There, now we can look at the crust from the side. You will see that it is also pretty thin. It is not
as thin as the wrapper though, because it needs to be thick enough to hold everything else inside it. The
lithosphere is the Earth's crust, the cool, hard layer on the outside of the Earth that is right under your
feet. Whoops. It looks like the next layer is dripping out . . . and burning holes in your pants.
Once you bite through the Earth's crust, you will see this thick, chunky, red stuff start to drip out. Oh, did I
mention that it is crazy hot? Hope you did not burn your hand. This layer is not as solid as the hard
chocolate, but it is not as runny as water either. It really is more like the filling in a chocolate . . . if that
filling were hot enough to melt rock. The mantle is the mostly solid, rocky-liquid layer of Earth right below
the crust. Unlike the crust, it still moves around, like stirred chocolate. It's a good thing the chocolate crust
is there to hold it in. That is, of course, unless there's a hole in the chocolate . . .
And does our crust have some holes. Volcanoes! Geysers! Long cracks at the bottom of the sea! These
are all holes in the crust where the mantle can leak out. The asthenosphere is the top part of the mantle
that leaks through the crust and also moves the crust around. It's the stuff that's just a few miles below
where we stand. You know it better as lava. No, this stuff does not make for good chocolate filling. It's
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Under Your Feet - magma, asthenosphere, lithosphere, mantle
much too hot and tastes nothing like strawberry or orange. The Earth tastes more like dirt and rock.
REALLY HOT dirt and rock.
Our chocolate Earth has one more part to it before we get to the middle. Below the stuff that leaks up
through the holes in the crust is stuff that's even hotter than lava. Magma is the name for lava when it's
still inside the Earth. The hotter it becomes, the more it will push up to the crust. Some of it will leak out
through the holes, while some will be cooled by the Earth's crust and turn back into rock. Some of the
crust will also get pushed down and melt into magma too. That's right, just like the filling in a chocolate
can be another kind of chocolate, lava is just melted rock. Your face looks a little red. Too hot?
If the Earth were a chocolate candy, the wrapper would be the air. The cool chocolate outside would be
the crust. The creamy filling would be the magma. And whatever drips out of the chocolate once you
have taken a bite would be the asthenosphere. Even hotter is the solid center of the Earth, but we have
not gotten that far down yet. You don't want to finish this? The center is just too hot? That's good. The
tiny chocolate people still need somewhere to live.
References:
Kids Fun Science. "Asthenosphere" Kids Fun Science, 2011.
<http://www.kids-fun-science.com/asthenosphere.html>
Windows to the Universe. "The Earth's Crust, Lithosphere and Asthenosphere" Windows to the Universe,
2012. <http://www.windows2universe.org/earth/interior/earths_crust.html>
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