Editing Divergent boundary (section)

== Description ==
{{Unreferenced section|date=September 2024}}
[[Image: Bridge across continents iceland.jpg|thumb|Bridge across the [[Álfagjá]] [[rift valley]] in southwest [[Iceland]], that is part of the boundary between the Eurasian and North American continental tectonic plates.]]

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 junction]]s is sometimes thought to be associated with the phenomenon known as [[hotspot (geology)|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.

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 [[East African Rift|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 fault]]s occur. These are the [[fracture zone]]s, many bearing names, that are a major source of [[submarine earthquake]]s. A seafloor map will show a rather strange pattern of blocky structures that are separated by [[:File: World Distribution of Mid-Oceanic Ridges.gif|linear features]] perpendicular to the ridge axis. If one views the seafloor 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]]).

It is at mid-ocean ridges that one of the key pieces of evidence forcing acceptance of the seafloor spreading hypothesis was found. Airborne [[Earth's magnetic field|geomagnetic]] surveys showed a strange pattern of symmetrical [[magnetic reversal]]s 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 [[Geomagnetic reversal|polar reversal]]s and the link was made by [[Lawrence Morley|Lawrence W. Morley]], [[Fred Vine|Frederick John Vine]] and [[Drummond Matthews|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.