The San Andreas fault is the 800 mile long boundary between the Pacific and North American Plates. It is the main fault of an intricate network of faults spanning the California coastal region. At its deepest, the San Andreas extends 10 miles beneath the ground. The San Andreas fault is a right-lateral transform fault meaning that if one was to stand on one side of the fault and look across to the other, the opposite site would appear to move to the right. This means the Pacific Plate is moving northward while the North American Plate is moving southward.

The Mid-Atlantic Ridge is a 10,000 mile long north-south mountain chain occupying the center of the Atlantic Ocean and passing through Iceland. It is the most extensively studied divergent plate boundary, dividing the North and South America Plates from the Eurasian and African Plates. In the divergent plate boundary, molten magma continuously rises from the mantle to the sea floor to fill in the gap formed by the diverging plates, and thus creating seafloor spreading. It is estimated that the Atlantic Ocean sea floor expands at a rate of 0.5 to 4 inches annually.

In addition to its divergent plate boundaries, the curving of the ridge also creates a number of transform fault lines. Occasionally, these transform faults are the site of seismic activity as the adjacent plates move in northern or southern directions.