The edge of a continent is found atthe boundary between low-densitycontinental rocks and higher-density oceanic rocks-The deepest parts of the oceans occur in elongate narrow trenches that areassociated withsubduction zones-Why do ocean water depths increase away from the midocean ridges?The accumulation of sediments over time adds weight to the sea floor. Older oceanic crust is denser and thus sits lower on the asthenosphere.-According to plate tectonic theory, the initiation of a rift zone is caused by the rise of hot mantle material toward the Earth's surface-Convection cells in the mantle form when hot mantle material rises, moves laterally, and then sinks when it becomes cold. Approximately 220 million years ago, the continents were joined together intoone supercontinent known as Pangaea. This super-continent was surroundedby an ocean named PanthalassaWhich of the following was the only process to occur during the last 65 millionyears?India rammed into Asia. The lateral spreading of the plates away from the elevated midoceanridge is driven in part bygravitational pullWhat led James Hutton to propose the the Earth must be extremely old?Henoted that natural processes, such as erosion, were very slow.