sustain (sustains 3rd person present) (sustaining present participle) (sustained past tense & past participle) 1 verb If you sustain something, you continue it or maintain it for a period of time. But he has sustained his fierce social conscience from young adulthood through old age... V n. ...a period of sustained economic growth throughout 1995.
If oceanic and continental crust collides the denser one which is the oceanic crust will be subducted, go underneath, the continental crust. The high heat of the mantle causes the oceanic crust to melt into magma. If the crust gets cracked this allows magma to rise and come out of the crust as lava which will form Volcanoes. When two continental crusts collide, the crust is forced to go upwards which forms mountains.
Magma tends to rise towards Earth's surface primarily because rocks  become less dense when they melt. The hotter the magma, the more  the rocks are likely to float, if yo â¦ u will.