There are many things about our own earth that still remain a mystery to us, and one of them is how the oceans were formed.Actually, we do not even know for sure how old the oceans are. It seems certain that oceans did not exist in the first stage of the earth growth. Perhaps they first came into being as clouds of vapor which turned into water as the earth grew cool. Estimates have been made of the ocean's age, based on the amount of mineral salt in the ocean today. These estimates range between 500,000,000, and 1,000,000,000 years.
Scientists are almost sure that most of the earth's land was covered by the sea at one time in the past. Some areas of the earth have been under water several times. But we do not know if any part of the deep ocean was ever land, or whether any land existing today was once beneath the deep ocean.
There is a great deal of evidence to show that certain parts of the land were once the bottom of shallow seas. For example, most of the limestone, sandstone, and shale found on land were deposited as sediment the chalk that is found in Kent, Sussex and Wiltshire was deposited on the bed of a sea. It is made up of the shells of tiny creatures that sank to the ocean bed to form what we call chalk.
Today, the waters of all the oceans cover nearly three-quarters of the surface of the earth. While there are many great ocean areas-where man has not yet explored the bottom or taken soundings, we have a good, rough idea of what the bottom is like. There are sections that are like mountain ranges, and there are plateaus and plains. But the ocean bottom is not as varied as the surface of the continents.
Scientists are almost sure that most of the earth's land was covered by the sea at one time in the past. Some areas of the earth have been under water several times. But we do not know if any part of the deep ocean was ever land, or whether any land existing today was once beneath the deep ocean.
There is a great deal of evidence to show that certain parts of the land were once the bottom of shallow seas. For example, most of the limestone, sandstone, and shale found on land were deposited as sediment the chalk that is found in Kent, Sussex and Wiltshire was deposited on the bed of a sea. It is made up of the shells of tiny creatures that sank to the ocean bed to form what we call chalk.
Today, the waters of all the oceans cover nearly three-quarters of the surface of the earth. While there are many great ocean areas-where man has not yet explored the bottom or taken soundings, we have a good, rough idea of what the bottom is like. There are sections that are like mountain ranges, and there are plateaus and plains. But the ocean bottom is not as varied as the surface of the continents.
