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Bursting with wildlife and teeming with mysteries to be solved, our oceans are one of the most amazing habitats on Earth. Take a deep breath, gang, as we dive into our ocean facts...
Top ten ocean facts

1. Around 70% of the planet's surface is covered by oceans. In fact, the oceans hold about 96.5% of all water on Earth.

2. The largest ocean on Earth is the Pacific Ocean, covering around 30% of the Earth's surface.

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3. The name "Pacific Ocean" comes form the Latin name Tepre Pacificum, "peaceful sea".

4. The deepest known area of the Earth's oceans is known as the Mariana Trench. It's deepest point measures 11km. That's a long dive down!

5. The world's oceans are home to incredible creatures that are masters of disguise! Take a look for yourself...

Did you know that we have a FREE downloadable ocean ecosystems primary resource? Great for teachers, homeschoolers and parents alike!

6. The longest mountain range in the world is found under water. Stretching over 56,000km, the Mid-Oceanic Ridge is a mountain chain that runs along the centre of the ocean basins.

7. About 70% of the oxygen we breathe is produced by the oceans.

For World Oceans Day, we chatted to young Nat Geo Kids readers to find out what they think about our amazing oceans... What do YOU think?

8. The sea is home to the world's largest living structure - the Great Barrier Reef. Measuring around 2,600km, it can even be seen from the Moon!

9. We have only explored about 5% of the world's oceans. There's a lot more to be discovered!

10. The sea can be described as the planet's mega museum. There are more artefacts and remnants of history in the ocean than in all of the world's museums combined! Pretty amazing, huh?

Did you know that we have a FREE downloadable Plastic Pollution primary resource, all about protecting our oceans and sea life? Great for teachers, homeschoolers and parents alike!

Video: TED2007
Photos: Getty Images UK

Did you enjoy our ocean facts? Let us know which one was your favourite by leaving a comment below!

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Find out ten amazing ocean facts right here at National Geographic Kids, like where's the deepest point in the ocean? Which ocean is the biggest?

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A waterfall is a place in a river where water spills suddenly downward. Waterfalls are known for their beauty and awesome power.

The world's tallest waterfall is Angel Falls, in Venezuela. Its water plunges 3,212 feet (979 meters). Angel Falls and other large waterfalls are sometimes called cataracts. Cataracts often drop straight down. The falling water may not even touch the rock behind it.

Smaller or less steep waterfalls may be called cascades. Cascades often fall over a number of short rock walls.

The action of flowing river water is one of the most common causes of waterfalls. Flowing water wears away the rock in a riverbed. Riverbeds sometimes contain areas of hard rock and areas of soft rock. In these cases the river wears away the soft rock before the hard rock. The hard rock that is left creates a steep wall. The river water plunges over the rock wall, forming a waterfall.

Waterfalls also form as a result of movements in Earth's crust. These movements can cause huge blocks of rock to rise or drop. This creates rock walls over which rivers may fall. Large, moving sheets of ice called glaciers also can cut away rock to form waterfalls.

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A waterfall is a place in a river where water spills suddenly downward. Waterfalls are known for their beauty and awesome power. The world's tallest waterfall is Angel Falls, in Venezuela. Its water plunges 3,212 feet (979 meters). Angel Falls and other large waterfalls are sometimes called cataracts.

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A waterfall is a river or other body of water's steep fall over a rocky ledge into a plunge pool below. Waterfalls are also called cascades.

The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls. Waterfalls themselves also contribute to erosion.

Often, waterfalls form as streams flow from soft rock to hard rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls.

A fall line is the imaginary line along which parallel rivers plunge as they flow from uplands to lowlands. Many waterfalls in an area help geologists and hydrologists determine a region's fall line and underlying rock structure.

As a stream flows, it carries sediment. The sediment can be microscopic silt, pebbles, or even boulders. Sediment can erode stream beds made of soft rock, such as sandstone or limestone. Eventually, the stream's channel cuts so deep into the stream bed that only a harder rock, such as granite, remains. Waterfalls develop as these granite formations form cliffs and ledges.

A stream's velocity increases as it nears a waterfall, increasing the amount of erosion taking place. The movement of water at the top of a waterfall can erode rocks to be very flat and smooth. Rushing water and sediment topple over the waterfall, eroding the plunge pool at the base. The crashing flow of the water may also create powerful whirlpools that erode the rock of the plunge pool beneath them.

The resulting erosion at the base of a waterfall can be very dramatic, and cause the waterfall to "recede." The area behind the waterfall is worn away, creating a hollow, cave-like structure called a "rock shelter." Eventually, the rocky ledge (called the outcropping) may tumble down, sending boulders into the stream bed and plunge pool below. This causes the waterfall to "recede" many meters upstream. The waterfall erosion process starts again, breaking down the boulders of the former outcropping.

Erosion is just one process that can form waterfalls. A waterfall may form across a fault, or crack in the Earth's surface. An earthquake, landslide, glacier, or volcano may also disrupt stream beds and help create waterfalls.

Classifying Waterfalls

There is not a standard way to classify waterfalls. Some scientists classify waterfalls based on the average volume of water in the waterfall. A Class 10 waterfall using this scale is Inga Falls, Democratic Republic of Congo, where the Congo River twists in a series of rapids. The estimated volume of water discharged from Inga Falls is 25,768 cubic meters per second (910,000 cubic feet per second).

Another popular way of classifying waterfalls is by width. One of the widest waterfalls is Khone Phapheng Falls, Laos. At the Khone Phapheng Falls, the Mekong River flows through a succession of relatively shallow rapids. The width of the Khone Phapheng Falls is about 10,783 meters (35,376 feet).

Waterfalls are also classified by height. Angel Falls, the world's tallest waterfall, plummets 979 meters (3,212 feet) into a remote canyon in a rain forest in Venezuela. The water, from the Gauja River, often does not reach the bottom. The fall is so long, and so steep, that air pressure is stronger often than the water pressure of the falls. The water is turned to mist before it reaches the small tributary below.
Types of Waterfalls
One of the most popular, if least scientific, ways to classify waterfalls is by type. A waterfall's type is simply the way the descends. Most waterfalls fit more than one category.

A block waterfall descends from a wide stream. Niagara Falls, in the United States and Canada, is a block waterfall on the Niagara River.

A cascade is a waterfall that descends over a series of rock steps. Monkey Falls, in the Indira Gandhi Wildlife Sanctuary and National Park in Tamil Nadu, India, is a gently sloping cascade. The waterfall is safe enough for children to play in the water.

A cataract is a powerful, even dangerous, waterfall. Among the widest and wildest of cataracts are the thundering waters of the Iguazu River on the border between Brazil and Argentina.

A chute is a waterfall in which the stream passage is very narrow, forcing water through at unusually high pressure. Three Chute Falls is named for the three "chutes" through which the Tenaya Creek falls in Yosemite National Park, California, U.S.

Fan waterfalls are named for their shape. Water spreads out horizontally as it descends. Virgin Falls is a striking fan waterfall on Tofino Creek, on Vancouver Island, British Columbia, Canada.

Frozen waterfall s are just what they sound like. For at least part of the year, the waterfall freezes. Mountaineers often climb frozen waterfalls as a challenging test of their skill. The Fang is a single pillar of ice in Vail, Colorado, U.S., that vertically plunges more than 30 meters (100 feet).

Horsetail waterfalls maintain contact with the hard rock that underlies them. Reichenbach Falls, a fall on the Reichenbach Stream in Switzerland, is a horsetail waterfall where legendary detective Sherlock Holmes allegedly fell to his doom.

Multi-step waterfalls are a series of connected waterfalls, each with their own plunge pool. The breathtaking "falling lakes" of Plitvice Lakes National Park, Croatia, are a series of multi-step waterfalls.

Plunge waterfalls, unlike horsetail falls, lose contact with the hard rock. The tallest waterfall in Japan, Hannoki Falls, is a plunge waterfall that stands 497 meters (1,640 feet). Hannoki Falls is seasonally fed by snowmelt from the Tateyama Mountains.

Punchbowl waterfalls are characterized by wide pools at their base. Wailua Falls is a punchbowl waterfall on the island of Kauai, Hawai'i, U.S. Although the plunge pool is tranquil and popular for swimming, the area around Wailua Falls itself is dangerous.

The water flowing over segmented waterfalls separate as distinct streams. Huge outcroppings of hard rock separate the streams of Nigretta Falls, a segmented waterfall in Victoria, Australia, before they meet in a large plunge pool.

Case Study: Niagara Falls

The Niagara River has two falls, one in the U.S. state of New York and one in the province of Ontario, Canada. Each waterfall is less than 60 meters (200 feet) tall, but together they are more than a kilometer (0.62 miles) wide.

Niagara and many other falls with large volumes of water are used to generate hydroelectric power. A tremendous volume of water flows over Niagara Falls, as much as 5,525 cubic meters (195,000 cubic feet) per second. Power stations upstream from the falls convert hydroelectric energy into electricity for residential and commercial use.

The U.S. and Canadian governments manage the Niagara River so carefully that it is possible for either country to "turn off" the falls. This is done at night, so as not to disturb the tourism industry, and the falls are never actually turned off, just slowed down. Water is diverted to canals and reservoirs, and the decreased flow allows engineers to check for erosion and other damage on the falls. U.S. and Canadian authorities also work together to ensure Niagara Falls doesn't freeze in the winter, which would threaten power production.

Because waterfalls are barriers to navigation, canals are sometimes built to get around them. Niagara Falls prevents passage between Lake Erie and Lake Ontario on the Niagara River. In the 19th century, the Welland Canal was built to make passage between the two Great Lakes possible.

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A waterfall is a river or other body of water's steep fall over a rocky ledge into a plunge pool below. Waterfalls are also called cascades. The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls. Waterfalls themselves also contribute to erosion.

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Kids learn about world rivers. The Nile, Amazon, Yangtze, Mississippi, Lena, Yellow, and Congo Rivers.

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Lakes and ponds biome is a type of freshwater aquatic biome. They are land areas filled with freshwater and surrounded by land. You can find ponds and lakes all over the world. In fact, there is one pretty close to you right now.

In general, ponds are smaller and shallower than lakes because ponds only last for a couple of weeks or months before drying out . Lakes, on the other hand , last for a much longer period of time. In fact, they can exist thousands or even millions of years!

Lake Baikal is the world's largest inland piece of freshwater in the world. It is over a mile deep and estimated to be over 25 million years old. The water temperature of ponds and lakes change from season to season. They will experience high temperatures during the summer and low temperatures during the winter .

Animals in the Lakes and Ponds Biome

You wont find a bunch of animal species in ponds and lakes. This is because each pond or lake can't interact with neighboring ponds or lakes. Why you may ask....because land is in the way.

For example, when was the last time you saw a fish jump out of the water and walk to another lake? , you said never. Since the land prevents animals from interacting with one another, it is hard for new species to form. As a result, the types of animals that you find in ponds and lakes are less diverse than in other aquatic biomes like oceans .

Next time you go out to a local pond or lake, take a look around. What types of animals do you see on-top, inside and around the water? For instance, on top of the water you may see mallard ducks, water skaters, or a long-necked cranes. Inside the water, you may see blue gill fish, snapping turtles, or tadpoles swimming around. And around the water, you may see snails, mosquitos, or earthworms. these animals live in the lake and pond biome.

Regions of Lakes and Ponds

Ponds and lakes are usually divided into three zones by depth and distance to the shoreline. The living environment and temperature among the zones are very different. As a result, different species occupy different zones.

Littoral zone is the part of water close to the shore, and it is also the warmest because it can absorb a lot of sun's heat. Thus, the littoral zone has the most diverse ecosystem with animals such as fish, insects, and amphibians . A lot of algae and aquatic plants are also found in the littoral zone. Living the littoral zone, can be dangerous. Since this region is shallow, animals that live in the littoral zone often times become food for snakes and birds .

Next, limnetic zone describes the open water area that is away from the shore and surrounded by the littoral zone . Limnetic zone is well lighted and occupied by plankton. Plankton are tiny organisms that float in fresh water. Plankton are important in the ecosystem because they are food for larger animals living in the pond or lake . In addition , a variety of freshwater fish also lives in the limnetic zone.

Last but not least, the profundal zone is the deep zone where sunlight cannot reach. With no heat, light or oxygen, the profundal zone, is a very hard place for animals to survive. For this reason, you will not find many animals down here.

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Lakes and ponds biome is a type of freshwater aquatic biome. They are land areas filled with freshwater and surrounded by land. You can find ponds and lakes all over the world. In fact, there is probably one pretty close to you right now.

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Massive iceberg breaks from Greenland glacier

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Time-lapse video shows a four-mile wide chunk of ice breaking away from the Helheim Glacier in Tasiilaq, Greenland, a rarely documented event called calving. Rough Cut (no reporter narration).