Water on Earth: Oceans, Rivers, and Ponds - First Grade Science
When astronauts look down at planet Earth from outer space, they see a breathtaking sphere painted in brilliant shades of blue, white, and green. In fact, Earth is often called the "Blue Planet" because liquid water covers more than 70 percent of its entire surface. Water is essential for all living creatures, supporting swimming fish, quenching the thirst of woodland animals, and nourishing crops. From the roaring waves of vast salty oceans to calm freshwater ponds in local parks, Earth's water bodies shape our landscapes and climate.
The Two Kinds of Water: Saltwater vs. Freshwater
Almost all the water on Earth is divided into two distinct categories based on whether it contains dissolved mineral salts.
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| SALTWATER VS. FRESHWATER |
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| SALTWATER (97% of Earth's Water) FRESHWATER (Only 3% of Earth) |
| - Contains high amounts of salt. - Contains little to no salt. |
| - Found in oceans and seas. - Found in lakes, rivers, ponds,|
| - Cannot be drunk by humans or rain, snow, and glaciers. |
| land animals. - Essential for drinking water. |
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The Salty Oceans
The vast majority of Earth's water is salty ocean water. Rivers wash tiny amounts of minerals and salts from rocks into the sea over millions of years. As water evaporates from the ocean surface into clouds, the salt remains behind, making ocean water taste very salty.
Precious Freshwater
Freshwater is rare and precious! Most of Earth's freshwater is frozen in massive polar ice sheets and mountain glaciers. Only a tiny fraction is accessible in flowing rivers, calm lakes, and underground wells for humans and land animals to drink.
Major Bodies of Water
Scientists categorize bodies of water based on their size, whether they are fresh or salty, and whether the water is flowing or standing still.
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| BODIES OF WATER OVERVIEW |
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| BODY OF WATER WATER TYPE MOVEMENT SCALE |
| Ocean Saltwater Waves/Currents Massive (covers planet)|
| Sea Saltwater Waves/Currents Large, partially land- |
| locked |
| River Freshwater Fast flowing Long, winding path |
| Stream / Creek Freshwater Flowing Narrow, shallow |
| Lake Freshwater Standing/Calm Large, surrounded by |
| land |
| Pond Freshwater Standing/Still Small, shallow |
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Oceans: The Giant Saltwater Basins
There are five interconnected oceans on Earth: the Pacific, Atlantic, Indian, Southern, and Arctic Oceans. Oceans are home to whales, sharks, coral reefs, and millions of marine creatures. Ocean currents also distribute heat around the globe, regulating Earth's climate.
Rivers and Streams: Water on the Move
A river is a large, natural ribbon of freshwater that flows downhill due to gravity. Rivers usually begin high in mountains from melting snow or bubbling underground springs (the source). As the river winds across land, it carves valleys and canyons before finally emptying into a lake or ocean (the mouth).
Lakes and Ponds: Still Waters
Lakes and ponds are inland bodies of water completely surrounded by land. A pond is small and shallow enough that sunlight can reach all the way to the muddy bottom, allowing water lilies and aquatic plants to grow across the entire pond floor. A lake is much larger and deeper, with dark, cold water at the bottom where sunlight cannot penetrate.
How Water Changes the Land
Flowing water is one of the most powerful sculpting forces on our planet.
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| WATER CARVES THE LANDSCAPE |
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| WEATHERING ---> Water cracks, dissolves, and chips rock pieces. |
| EROSION ---> Flowing river current picks up sand and mud. |
| DEPOSITION ---> River slows down and drops sediments at mouth, |
| building rich triangular lands called deltas. |
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Over millions of years, the rushing waters of the Colorado River carved through solid stone layers to create the magnificent Grand Canyon, a canyon over a mile deep!
Chapter Review Exercises
Question 1: What percentage of Earth's surface is covered by water, and why is Earth called the "Blue Planet"?
Question 2: What is the main difference between saltwater and freshwater, and where is each type found?
Question 3: Explain the difference between a river and a pond in terms of water movement and surrounding land.
Question 4: How can flowing water in a river change the shape of solid rock over long periods of time?
Solutions and Explanations
Solution 1: Over 70 percent of Earth's surface is covered by liquid water. Earth is called the "Blue Planet" because from outer space, the vast oceans reflect blue sunlight, giving the planet a brilliant blue appearance.
Solution 2: Saltwater contains high amounts of dissolved mineral salts and is found in vast oceans and seas; it cannot be drunk by humans. Freshwater contains almost no salt and is found in rivers, streams, lakes, ponds, and polar ice caps; it is the water necessary for land life to drink.
Solution 3: A river is a flowing body of freshwater that travels downhill along a winding path toward an ocean or lake. A pond is a small, shallow body of still (non-flowing) freshwater that is completely surrounded by land.
Solution 4: Flowing water carves solid rock through erosion. As river currents push pebbles, sand, and water against rocky riverbeds, the constant grinding chips away microscopic bits of stone, carving deep channels, valleys, and canyons over millions of years.