1. One Big Ocean

The Earth has one big ocean with many features

We live on a blue planet. The ocean is the Earth’s most dominant feature. It is seen all the way from space. Our planet's surface is 70% ocean. Earth's highest peaks and deepest valleys are all in the ocean and 97% of the water on the planet is in the ocean! There are five main ocean basins: the Pacific, Atlantic, Indian, Southern, and Arctic. All of these ocean basins are connected through the movement of water, creating One Big World Ocean

Water is moved around the planet by our Earth’s spin, the pull of gravity, differences in temperature, and transforming processes like evaporation and condensation. Salt water, fresh water, cold water, warm water, it is all linked through the water cycle. Water is everywhere, even inside human beings. Even still, we are always learning more about water’s properties and how water behaves.


While the ocean is the most dominant body of water on the planet, fresh water plays an important role in the water cycle as well. Seawater and freshwater have different properties.

Seawater has unique properties: it is saline (salty), it's freezing point is slightly lower than fresh water, it's density is slightly higher, it's electrical conductivity is much higher, and it is slightly basic (the opposite of acidic).

The salt in seawater comes from a variety of different sources. When rocks break down, or erode, it releases minerals into the water. These minerals are transported to the ocean through rivers and streams. Volcanic eruptions also release salt into the water. Minerals from thousands of years ago are also recycled into the ocean through reactions at the sea floor. Salt entered the ocean millions of years ago when it formed and has been around ever since.

Freshwater does not have high salinity like saltwater. Freshwater does play an important role in cycling nutrients and water back into the ocean and helps to balance the salt levels of the ocean. Freshwater is not as easy to find on our planet.

The ocean is connected to major interior lakes, rivers, and watersheds through the water cycle. Rivers and streams transport nutrients, salts, sediments, and pollutants from watersheds to estuaries and to the ocean. An estuary is where a freshwater source and the saltwater ocean meet. Estuaries create excellent habitats for a wide diversity of organisms. Play the Where the River Meets the Sea Game to learn more about estuaries and earn a badge.

You can see that all water on earth is connected, salt and freshwater, and it all originates in the ocean. Without the ocean and it's relationship with freshwater watersheds and the atmosphere, the cycling of water around the earth would not be possible. Although the ocean is large, and may even seem infinite at times, it is important to remember that it is in fact finite. For the first time scientists were able to measure the ocean which we now know contains 1.3 billion cubic kilometers of seawater. This means that the resources of the ocean have a limit.

After you have played the Where the River Meets the Sea Game, you may take the One Big Ocean Quiz to review your knowledge and earn your first badge.


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