The Earth has the greatest mass of the rocky planetsΓÇöa fact that has profoundly affected its development. The planet has a relatively hot, dense, molten inner core surrounded by a semimolten mantle that extends from the core to near the surface. Large areas of light rock, which form the continents, extend to the bottom of the oceans and float atop heavier rock known as basalt, which forms the bases of the oceans. The different areas of this light rock, known as plates, rub against and collide with one another, causing earthquakes and creating mountain ranges. The movements of these plates over hundreds of millions of years has created the present-day continents.
