🌊 Oceans and Seas: A Trip Around the Watery World 🌍

Oceans, Seas, and More

• Oceans and seas are huge amounts of salty water.

• They cover more than 70% of our Earth. That means the Earth is mostly water!

• They are super important for keeping our planet healthy.

• They have big, natural animal homes inside them called ecosystems.

• The seas and oceans are the biggest natural places on Earth.

• They are important to everyone, even if you don't live near a beach! 🏖️

Oceans

• Oceans are the biggest parts of salty water on Earth.

• They are very deep. They are, on average, more than 3,700 meters deep!

Seas

• Seas are smaller bodies of saltwater.

• They are often found right next to the land.

• Seas are not as deep as oceans. They are usually less than 1,000 meters deep.

The Five Oceans

The Earth has five main oceans:

1. The Pacific Ocean

2. The Atlantic Ocean

3. The Indian Ocean

4. The Southern Ocean

5. The Arctic Ocean

The Pacific Ocean 🐳

• The Pacific Ocean is the biggest ocean. It is also the deepest ocean.

• It covers about 45 out of every 100 parts of all the ocean water.

• It is about 165 million km² (square kilometers) big.

• Its water touches North America, South America, East Asia, Australia, and the Southern Ocean.

• The Mariana Trench is in the Pacific Ocean. This is the deepest place on our whole planet!

The Atlantic Ocean 🚢

• The Atlantic Ocean is the second-largest ocean.

• It covers about 26% (about a quarter) of all the world’s water area.

• It sits between the Americas (North and South) in the west and Europe and Africa in the east.

• It connects to the Arctic Ocean in the north and the Southern Ocean in the south.

• The Atlantic has many kinds of sea life, or biodiversity. This includes seals, whales, dolphins, and lots of fish.

The Indian Ocean 🐠

• The Indian Ocean is the third-largest ocean.

• It is about 69 million km² in size.

• It lies between Africa, India, South-East Asia, and the Southern Ocean.

• The deepest place here is called the Java Trench.

The Southern Ocean 🧊

• The Southern Ocean is the water that goes all the way around the huge, icy land of Antarctica.

• It connects to the Atlantic, Indian, and Pacific Oceans.

• It is a very cold ocean! The water temperature is usually between 10 degrees C and -2 degrees C (minus 2 degrees Celsius).

• It is home to animals like penguins, whales, and seals.

The Arctic Ocean 🐻‍❄️

• The Arctic Ocean is the smallest ocean. It is also the coldest one.

• It is about 14 million km² big.

• Most of this ocean is covered by sea ice, especially in the cold winter.

• Animals like polar bears, seals, and fish live here.

A Few Seas

Arabian Sea

• The Arabian Sea is a very large arm of the Indian Ocean.

• It sits between India, a big land called the Arabian Peninsula, and East Africa.

• It is about 3.3 million km² in size.

Black Sea

• The Black Sea is a big sea that is almost all surrounded by land.

• It connects to the Mediterranean Sea through a tiny water path called the Turkish Straits.

• It is about 444,000 km² in size.

Baltic Sea

• The Baltic Sea is a sea that is almost closed off by land (semi-enclosed).

• It is between a land called the Scandinavian Peninsula and Central Europe.

• It is less salty than the open ocean because many rivers flow into it.

• In winter, parts of the sea sometimes get covered in ice.

Ocean Features: Shapes of Water and Land

Gulf

• A gulf is a deep and large part of the ocean that is mostly surrounded by land.

• It has a narrow opening that lets it connect to the main ocean.

• Gulfs often form when the Earth's plates (pieces of the crust) move slowly.

• The Persian Gulf is a famous example.

Bay and Bight

• A bay is a part of the sea that has land around it but is wide open to the rest of the ocean.

• Bays are usually smaller than gulfs.

• The Bay of Bengal is one of the world's largest bays.

• A bight is like a very wide bay. The Great Australian Bight is a huge one.

Strait or Channel

• A strait is a narrow river of water that connects two bigger bodies of water.

• The Strait of Gibraltar connects the Atlantic Ocean to the Mediterranean Sea.

• The English Channel is an example of a channel, which is a strait that is a bit wider.

Peninsula 🗺️

• A peninsula is a piece of land that has water all around it on three sides.

• The Arabian Peninsula is the largest one in the world.

• Other examples are the Malay Peninsula and the Florida Peninsula.

Isthmus

• An isthmus is a very narrow strip of land that connects two large landmasses.

• It has water on both of its sides.

• The Isthmus of Panama connects North America and South America.

The Bottom of the Ocean

The Continental Shelf

• This is the land that is underwater right next to a continent.

• It is relatively shallow (not very deep).

• It usually extends for about 200 meters deep.

The Continental Slope and Continental Rise

• The continental slope starts where the shelf ends. It drops steeply down to the deep ocean floor.

• The continental rise is a gentle slope at the very bottom. It is made up of dirt and rock (sediments) that have piled up there.

Mid-Ocean Ridges

• The ocean bottom has long, long lines of underwater mountains. These are called mid-ocean ridges.

• They are made when the Earth's strong plates move away from each other.

• The Mid-Atlantic Ridge is the longest one.

Abyssal Plains

• These are the very flat and deep parts of the ocean floor.

• They are covered with mud and the tiny pieces of dead sea creatures.

• Sometimes, they have small hills called abyssal hills.

Trenches

• Trenches are very deep, narrow valleys in the ocean floor.

• They are formed when two Earth plates crash together, and one plate slides under the other. This sliding is called subduction.

• The Mariana Trench is the deepest place on Earth.

Volcanic Activities 🔥

• Seamounts are single, underwater mountains that pop up from the ocean floor but do not stick out of the water.

• A guyot is a seamount that has a flat top.

• A volcanic island arc is a curved line of volcanic islands. They form when two plates meet.

The Movement of the Ocean 🌊

Currents

• Currents are like rivers of water that move in one direction through the ocean.

• They move because of gravity, wind, and the way the Earth spins.

• Surface currents are on the top of the water. They are mostly pushed by the wind.

• Thermohaline circulation is the very slow movement of deep ocean water. It moves because of how warm (thermo) and salty (haline) the water is. This movement is like a giant conveyor belt that moves heat all around the world and helps control the weather.

Waves

• Waves are the water moving up and down on the sea's surface.

• They are mostly caused by the wind.

• The highest part of a wave is called the crest. The lowest part is the trough.

• Tsunamis are huge, scary waves caused by big things like an underwater earthquake or a volcano erupting.

Tides 🌙

• Tides are when the sea level rises (gets high) and falls (gets low) in a regular way.

• This happens about twice a day.

• Tides are caused by the Moon's gravity pulling on the Earth's water.

• The Sun's gravity also pulls and changes the tides.

• Spring tides (extra-high high tides) happen when the Sun, Moon, and Earth are in a straight line.

• Neap tides (not-so-high high tides) happen when the Sun and Moon are at a right angle to the Earth.

Life in the Ocean 🐡

Ocean life is split into three main groups:

1. Plankton: These are tiny plants and animals that just float on the water. They can't really swim where they want to go. Phytoplankton are the plant plankton, and zooplankton are the animal plankton.

2. Nekton: These are the strong swimming animals that live in the open ocean. They can move wherever they want to go. Examples are whales, seals, sharks, and fish.

3. Benthos: These are the animals and plants that live on the bottom of the ocean floor. Examples are crabs, starfish, sponges, and seaweed.

Ocean Zones

The ocean water has three main layers based on how much light they get:

• Sunlight Zone: This is the top part. It goes down about 200 meters (660 feet). It gets the most light.

• Twilight Zone: This middle part is from 200 meters to 1,000 meters deep. Only a little, dim light gets here.

• Dark Zone: This is the deepest part, below 1,000 meters. No sunlight reaches here, so it is super cold and dark.

Watery Regions

The different zones also have different temperatures (how warm or cold they are).

• Tropical Life: The warmest ocean water is near the equator (the tropics). This area has the most different kinds of sea animals and plants, like the coral reef "rainforests" of the sea.

• Temperate Life: The water here is cooler than in the tropics. Many animals here, like certain fish, move (migrate) to warmer seas when winter comes.

• Polar Life: The water here is the coldest. Animals like walruses and polar bears have very thick fat (blubber) to keep themselves warm.

Resources from the Ocean 🎣

Marine and Inland Fishing

• Fishing is important because it gives people food and jobs.

• More fishing happens in coastal areas (near the land) because that's where the most fish live.

• Sometimes, people catch too many fish too quickly. This is called overfishing.

• Governments and groups like the United Nations (UN) try to make rules about fishing so the fish don't disappear.

Seaweeds

• Seaweed is a very useful plant that grows in the ocean.

• It is used in food (like sushi!), make-up, food for farm animals, and even to help plants grow (fertilizer).

• A type of seaweed called kelp can grow very tall. It is used in things like jelly, ice cream, and salad dressing.

Extraction of Fuels ⛽

• Oceans hold big amounts of energy and fuel like crude oil, natural gas, and coal.

• These are taken out of the ocean floor.

• But, this digging can be dangerous and hurt the ocean.

Seafloor Minerals

• Minerals are useful materials. The ocean floor has minerals like manganese, copper, nickel, and cobalt.

• These minerals are found in round shapes called nodules on the deep ocean floor.

• Mining companies want to dig them up and use them.

Fresh Water and Desalination

• Ocean water is too salty to drink, but people need fresh water for drinking and farms.

• Desalination is a special process to take the salt out of seawater to make it fresh.

• Countries that don't have much fresh water, like Saudi Arabia and Kuwait, use big desalination plants to get drinking water.

Tidal and Wave Energy ⚡

• Tidal energy is electricity made from the tides moving in and out.

• Tides are very powerful and can make clean, new energy.

• Wave energy is electricity made from the strong push of ocean waves.

Threats to the Ocean 🗑️

Overfishing

• Overfishing means catching too many fish, too fast.

• This has made fish numbers go down. About one-third of all fish populations are now overfished.

• The large nets used by big fishing boats (trawlers) can also hurt other sea animals and the ocean's natural homes.

Rising Sea Level

• Global warming (the Earth getting hotter) is causing the sea level to rise.

• The oceans get warmer and melt ice, like glaciers and icebergs.

• This makes the sea level rise, which threatens people who live near the coasts.

Overwarming

• The oceans soak up a lot of the extra heat we create (by using fuel).

• This extra heat makes the ocean water warmer and also makes it more acidic (less healthy for sea animals like coral).

Domestic and Industrial Waste

• People throw their trash into the ocean, which harms animals and plants.

• Pollution from farms (like special plant food and bug-killer) flows into the ocean.

• Waste from factories and cities is also dumped into the ocean.

• This pollution hurts the many kinds of sea life (biodiversity).

Oil Spills 🛢️

• Oil spills happen when oil leaks from ships or oil rigs into the ocean.

• Oil is very toxic (poisonous) and kills many birds and animals.

• Cleaning up the oil takes a very long time.

Sustainable Management of Oceans 💚

Sustainable means using things in a way that is good for us now and keeps it safe for people in the future.

• Governments and other groups are working hard to protect the oceans.

• We need to teach everyone about how important the oceans are.

How we can help:

• Protect ocean life by making special areas where no one can fish (marine parks).

• Stop destructive fishing like using poisons or explosions to catch fish.

• Support sustainable fishing (rules that help keep fish populations strong).

• Stop companies that dump waste.

• Put limits on fishing so that baby fish can grow (discourage catching baby fish).

• Help local groups and people who live near the coast to reduce pollution and clean up trash.