Why is there more land in the Northern hemisphere?

The continents are in motion due to plate tectonics, moving very very slowly in relation to each other and the oceans. In the past, all of the continents were one gigantic landmass at least once. They moved apart and currently most of them are nearer the North Pole. This is likely to change again over a period of hundreds of millions of years.

When the dinosaurs roamed the earth, the continents were connected differently than they are now, and were in different locations on the globe. India, for example, was sitting closer to the South Pole.