Editing Volcano (section)

===Divergent plate boundaries===
{{Main|Divergent boundary}}
[[File:Spreading ridges volcanoes map-en.svg|thumb|upright=1.8|Map showing the divergent plate boundaries (oceanic spreading ridges) and recent sub-aerial volcanoes (mostly at convergent boundaries)]]

At the [[mid-ocean ridge]]s, two [[list of tectonic plates|tectonic plates]] diverge from one another as hot mantle rock creeps upwards beneath the thinned [[oceanic crust]]. The decrease of pressure in the rising mantle rock leads to [[adiabatic]] expansion and the [[partial melting]] of the rock, causing volcanism and creating new oceanic crust. Most [[divergent plate boundaries]] are at the bottom of the oceans, and so most volcanic activity on Earth is submarine, forming new [[seafloor]]. [[Black smoker]]s (also known as deep sea vents) are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea level, volcanic islands are formed, such as [[Iceland]].{{sfn|Schmincke|2003|pp=17-18, 276}}<ref name=mor/>