Did you know that the Earths longest mountain
range is underwater? The Mid-Ocean Ridge system,
shown above snaking its way between the continents,
is more than 56,000 kilometers (35,000 mi) long.
This series of mountains and valleys marks where
the Earths crustal plates are moving apart.
The driving force behind the process of plate
tectonics is heat generated deep inside the earths
core by radioactive decay. This heat reaches the
surface primarily along the Mid-Ocean Ridge. One
of the earths most dramatic topographical
features, the Mid-Ocean Ridge is a continuous
range of undersea mountains more than 12,000 feet
high and 1,200 miles wide winding through 40,000
miles of the worlds oceans. It is here,
at Mid-Ocean Ridges, that new sea-floor crust
is produced and much of the earths internal
heat is released.
At Mid-Ocean Ridges, two plates are pulling apart
from each other as hot magma (liquid rock) emerges
from the mantle and oozes forth as lava to fill
the crack continuously created by plate separation.
The lava cools and attaches itself to the trailing
edge of each plate, forming new ocean floor crust
in a process commonly known as sea-floor spreading.
All plates have a so-called leading edge
and trailing edge. The leading edge
is simply the front of the plate, that edge which
leads the plate in the direction that
it is moving. The trailing edge is the back end
of the plate. At Mid-Ocean Ridges new crust is
added to the trailing edge of each of the two
separating, or diverging, plates. Hence, the further
sea-floor crust is from the mid-ocean ridge, the
older it is.
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