It is constantly being produced at the bottom of the oceans in places called mid-ocean ridges&#151;undersea volcanic mountain chains formed at plate boundaries where there is a build-up of ocean crust.
(places; called; mid-ocean ridges&#151) (undersea volcanic mountain chains; formed; L:at plate boundaries) Context(undersea volcanic mountain chains formed,List([99, 139))):(It; is being produced; L:at the bottom of the oceans in places; T:constantly)
undersea volcanic mountain chains formed,List([99, 139))
places undersea volcanic mountain chains It
called formed is being produced
mid-ocean ridges&#151
L:at plate boundaries
L:at the bottom of the oceans in places T:constantly