Slide 31 of 49

Recent evidence tells us that the earth is unique in many ways, even compared to the other rocky planets in our Solar System. In a recent study, Dr. Roberta Rudnick says that the earth has a unique continental crust, which is different from any other planet in our Solar System (even Venus, our "sister planet"). The mechanisms which resulted in this unique continental crust is not entirely certain as she stated, "Perhaps the greatest dilemma facing those interested in understanding how the continents formed is their composition." The tectonic processes which recycle the crust are extremely important in maintaining life on our planet by recycling minerals and nutrients. Normally, during planet formation, the crust covers the entire planet. Under these conditions, the crust cannot move, since there is no free space for it to do so. However, since a large amount of the earths primordial crust was blasted into outer space by the collision that formed the moon, there was space for the original continent (Pangea) to move and even break up into additional land masses. Because of tectonic activity, continents can exist on a planet that would normally be a water world. Without tectonic activity, the original continent would have eroded into the large ocean, never to be seen again. In fact, planets with large amounts of water are always water worlds because of erosion.