posted on Aug, 31 2011 @ 08:18 AM
It's a tectonic plate boundary. The ones you are referring to are referred to as divergent with sea-floor spreading. They do create rifts as
mentioned previously, but, more importantly, the "zig" and "zag" features you see are areas along the boundary zone where transform (or
strike-slip) movement pulls the edge of the plate in opposite directions.
The entire earth's crust is covered with these boundary zones, much like the cracked shell of a hard-boiled egg. The cracked crustal plates move
about because the molten magma beneath is constantly rising toward the surface as it moves up away from the central heat source, cools, and then heads
back down again to be reheated. This creates a convection current of material upon which the crustal plates are sliding around. Inevitably the edges
of the these plates bump up against each other, slide along each other, or pull away from one another. This is why we have most of the volcanoes and
earthquakes on the planet at the boundary zones of these plates and their consequent interaction.
One of the largest of these plate boundary cracks is at the mid-atlantic ridge, where new ocean-sea floor is created and material moves up to the
surface and away from each other. The activity causes the continents to separate, increasing the size of the Atlantic while also forcing Africa and
South America to bump-and-grind against adjacent plates.