<P> Over millions of years, tectonic plates may move many hundreds of kilometers away from both sides of a divergent plate boundary . Because of this, rocks closest to a boundary are younger than rocks further away on the same plate . </P> <P> At divergent boundaries, two plates move away from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below . The origin of new divergent boundaries at triple junctions is sometimes thought to be associated with the phenomenon known as hotspots . Here, exceedingly large convective cells bring very large quantities of hot asthenospheric material near the surface and the kinetic energy is thought to be sufficient to break apart the lithosphere . The hot spot which may have initiated the Mid-Atlantic Ridge system currently underlies Iceland which is widening at a rate of a few centimeters per year . </P> <P> Divergent boundaries are typified in the oceanic lithosphere by the rifts of the oceanic ridge system, including the Mid-Atlantic Ridge and the East Pacific Rise, and in the continental lithosphere by rift valleys such as the famous East African Great Rift Valley . Divergent boundaries can create massive fault zones in the oceanic ridge system . Spreading is generally not uniform, so where spreading rates of adjacent ridge blocks are different, massive transform faults occur . These are the fracture zones, many bearing names, that are a major source of submarine earthquakes . A sea floor map will show a rather strange pattern of blocky structures that are separated by linear features perpendicular to the ridge axis . If one views the sea floor between the fracture zones as conveyor belts carrying the ridge on each side of the rift away from the spreading center the action becomes clear . Crest depths of the old ridges, parallel to the current spreading center, will be older and deeper...(from thermal contraction and subsidence). </P> <P> It is at mid-ocean ridges that one of the key pieces of evidence forcing acceptance of the seafloor spreading hypothesis was found . Airborne geomagnetic surveys showed a strange pattern of symmetrical magnetic reversals on opposite sides of ridge centers . The pattern was far too regular to be coincidental as the widths of the opposing bands were too closely matched . Scientists had been studying polar reversals and the link was made by Lawrence W. Morley, Frederick John Vine and Drummond Hoyle Matthews in the Morley--Vine--Matthews hypothesis . The magnetic banding directly corresponds with the Earth's polar reversals . This was confirmed by measuring the ages of the rocks within each band . The banding furnishes a map in time and space of both spreading rate and polar reversals . </P>

What type of fault does a divergent boundary have
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