If all of this is new to you, here's the short version.
The theory of plate tectonics says that the crust of the earth is not
whole and unmoving, like the surface of a ball. It's more like a
cracked egg shell. Between the cracks are large pieces of the surface
called plates. These plates are very slowly moving--about an inch per
year.
The edges of the plates are said to be constantly but
very slowly emerging as liquid rock from earth's hot core. Versions
of this have been observed on the ocean floor, where lava boils up
into the water and cools into hard rock.
Plate tectonic theory says that earthquakes and
volcanoes are caused by shifts in the earth's plates most often occur
at or near the plate boundaries.
The blue and green dots represent locations of
earthquakes and volcanoes. Notice, some plate edges almost match the
outlines of continents. They meet at the western edge of North and
South America (to the right of center).
In the picture below, can you see five continents?
Notice, on the right, the plate outlines that appear to
match the outline of the African continent. Are there any others that
do that?
