How many oceans are there? If you ask several people this question you may be surprised to find out that they could each give you a different answer. One That is because the ocean is a one continuous body of water encircling the Earth. This animated map shows the possible interpretations of the ocean. The world ocean is commonly divided into areas based on their geographic location. Five oceanic regions are often designated: Pacific, Atlantic, Indian, Arctic and Southern. Four Sometimes the Southern Ocean is included with the waters that border it, the Pacific, Atlantic and Indian oceans. Three The Arctic is sometimes incorporated into the waters that are closest to it, the Atlantic and Pacific.

The Earth's Hydrological Cycle, also known as the Water Cycle, is a closed system. That means, for all practical purposes, the water that we have on our planet is all the water we are going to have. The water moves through the water cycle from ocean to land and back again (see diagram above). The same water that we use today could have been slurped by dinosaurs millions of years ago. The hydrological system filters and cleanses the water as it passes through the various stages.

Most of the water on Earth (97%) is in the ocean. Only 3% is fresh water. Less than 1% of that is surface water. With so little of the planet's water readily available to use, it is vital that we protect and conserve our water supply.

References: The Water Cycle diagram courtesy of the US Geological Survey. A printer friendly version as well as several activities are available at USGS Water Science for Schools: The Water Cycle.

The Distribution of Earth's Water can be found at Water Science for Schools: Earth's Water under the heading Where is Earth's Water.