Earth Plate Movement
Country: United States
Date: May 2006
If the Earth's plates are moving so slowly then
how did Mt. Everest become so high?
Let's use the analogy of a car versus a bulldozer. The car can certainly go
much faster, but it doesn't have the power to push, pull or move the amount
of dirt that the bulldozer does. The Earth's plates are so massive that the
momentum that they have is very high. Momentum is velocity time mass, or p
= mV. Even though the velocity is a very very small number, the mass of a
techtonic plate is so much higher that the momentum ends up being
enormous! When two of these plates start pushing into each other, the dirt
and rock that is in the interface can't hold up to that amount of
pressure. So it ends up splitting and moving upward, thus creating
mountains. Everest is so high because the two plates that are involve have
been pushing the mountain up for so long and errosion has been minimal
compared to the rate of growth of the mountain.
It is a very slow process---taking millions of years. The Earth is so old
that other mountain ranges were uplifted and eroded away again, leaving
evidence in sedimentary rocks. In many more millions of years, Mt. Everest
will be gone, as well, but for now, it just keeps getting taller (because of
plate collision) faster than it is eroding away.
This is a problem most of us have with trying to imagine geologic time.
Things happen so slowly, we don't really observe it (except when we compare
data from measurements over long periods and doing precise measurements that
reveal even minute changes), that it becomes hard to imagine something
happening at all. However, you already understand that the movement of the
plates can cause major changes in the shape of the surface. You already
understand that this is a powerful force. I think you just need to imagine
this as happening over a very long and continuous period to realize that
mountains can form.
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Update: June 2012