|
|
Structure of earth |
|
The Earth is not solid all the way through like an apple but has layers which are solid and others which are really quite runny. |
|
Structure of
earth The Earth is not solid all the way
through like an apple but has layers which are solid and
others which are really quite runny.
Imagine a bowl of hot custard with a
thick skin on top (yuk!). We live on top of the skin, known
as the crust, but beneath our feet it's hot and gooey. The
skin is really thick in most places (30 to 50 Km) and most
of us never get to see the custard but in some places the
skin is very thin. The temperature in the core is about 3000 degrees
Centrigrade! That is HOT! In fact the crust of the Earth is
made up of several large "skins" , (like jigsaw pieces) and
it's at the place where the edges meet that there is most
likely to be a hole that lets the custard through. Of course
it's not really custard - it's liquid rock, known as magma.
The magma under the Earths crust is
so hot (more than 1000 degrees Celcius) that pressure builds
up, seeks out a weak spot, and bursts out. This eruption can
be quite slow like a simmering pot of water (a shield
volcano) or can be fast and explosive like a pressure cooker
with a jammed relief valve (an andesite volcano).
