Choose the correct answer from each drop-down menu to complete the statement. Tectonic plate movement is driven by several forces. [Dropdown 1] occurs at mid-ocean ridges where new crust forms and gravity causes it to slide away, pushing plates apart. In contrast, [Dropdown 2] forces plates downward into the mantle at subduction zones due to the density of the sinking edge. The process where one plate sinks beneath another is known as [Dropdown 3] , which often leads to volcanic activity and deep-sea trenches.