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Our Earth
is a warm planet sailing through cold space. Much of the rocky interior
(the mantle) of our planet is hot enough to flow, like a candy bar kept
too long in one’s pocket. The surface of the Earth, however, is chilled
by the cold of space, and so the familiar rocks of the Earth’s surface
are hard and brittle. The cold outer layer of our planet, which holds
together as a rigid shell, is not made of one solid piece. Instead this
shell is broken into many separate pieces, or tectonic plates, that slide
around atop the mobile interior.
The tectonic
plates are in motion. They are driven by the flowing mantle below and
their motions are controlled by a complex puzzle of plate collisions around
the globe. There are three types of plate-plate interactions based upon
relative motion: convergent, where plates collide, divergent, where plates
separate, and transform motion, where plates simply slide past each other.
Seafloor Spreading is the usual process at work at divergent plate boundaries,
leading to the creation of new ocean floor. As two tectonic plates slowly
separate, molten material rises up from within the mantle to fill the
opening. In this way the rugged volcanic landscape of a mid-ocean ridge
is created along the plate boundary.
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