The Atlantic Ocean opened, India reached Asia, and large inland seas subdivided the continents. At the end of the period mass extinctions occurred, Ammonites, marine reptiles, pterosaurs, and dinosaurs disappeared. The Cause of Tides Ocean tides occur twice per day. They are caused by the effects of the moon's gravity on earth's oceans. The pull from the moon actually distorts the oceans into an oval shape.
Water piles up on both the side facing the moon and on the opposite side.
On the moon's near side it is pulled towards the moon while on the opposite side, where the lunar gravity is weaker, it drifts away. These two bulges remain stationary over the time it takes earth to rotate. As a result there are two tides each day. During November 2000 these great planets will be close together in the same part of the sky, in Taurus. These two planets coming together is called a Great Conjunction.