If you've ever visited the beach, you know that the oceans are very salty. But do you know why? According to geologists, there are many natural processes that over the millions of years transport salt from different places around the world and deposit it in the oceans.

Rivers are responsible for the largest portion of salt in the oceans today. They take salt out of eroded rocks and transport it to the oceans.

Pangea was a supercontinent that existed around 250 million years ago. It was located near present-day Antarctica and has slowly drifted apart, forming the seven continents we now recognize today. Because of the tectonic plates, the continents are still moving and will eventually look much different than they do today.

Waves are the result of wind blowing across water. Though it may not look like it, waves are the simple up and down movement of water due to the friction of air. As waves get closer to the shore, they get steeper and steeper and  sometimes break once they reach land.

Because Earth's climate is always changing, scientists believe there will be another Ice Age someday, where ice will cover the land at higher latitudes and elevations. Unfortunately, nobody can predict when the next Ice Age will occur; it may be in a hundred years or it may be thousands of years in the future.

Today about 70 percent of the Earth's surface is covered by water. The other 30 percent of Earth's surface is land located mainly in the Northern Hemisphere. The Southern Hemisphere has a great deal of ocean. Looking at a globe, you can see the tremendous difference.

The Nile River, located in Egypt, is the longest river in the world. The Nile stretches 4,100 miles from it's sources and has been the center of Egyptian civilization from its beginning thousands of years ago. Following the Nile in length are the Amazon River in Brazil, The Missouri-Mississippi in the United States, and the Yangtze in China.

Yes. Scientists call soil that is frozen most or all of the time permafrost. Permafrost occurs in places around the world with very cold climates, usually in higher latitudinal regions.

It seems impossible to live lower than sea level when we first think about it, yet many people do. This is possible because they live in areas too far away from the sea to be flooded with water. These areas of land are forced below sea level by movement of tectonic plates.