OCEANS ON EARTH

OCEANS ON EARTH

HOW WERE THE OCEANS FORMED?

The oceans were formed over vast periods of time.Billions of years ago, the Earth was incredibly hot, and covered with volcanoes.

Volcanoes spit out a lot of chemicals when they erupt, and they get those chemicals from deep inside the Earth. 

2 of those chemicals are hydrogen and oxygen.When those combine, they make water. The Earth also got water from comets. Many comets are actually made of ice, which becomes water when it melts! 

Over billions of years, erupting volcanoes and crashing comets caused water to form on Earth. But because the Earth was so hot, the water was in the form of water vapor.
As the Earth gradually cooled, the atmosphere also became cooler, and the water vapor began to condense to form clouds.As the cooling continued, the clouds turned to rain. This rain fell continuously - not for days, weeks, months or years, but for centuries!
The water that fell on the ground did not fly off the surface, because of the force of gravity. As a result, this water began to accumulate in the hollows of the Earth's surface, and the oceans were formed.

HOW MANY OCEANS ARE THERE?

Our planet contains more water than land in fact, 71% of the Earth is covered by oceans. There are 5 oceans - the PACIFIC, ATLANTIC, INDIAN, ARCTIC, and SOUTHERN Oceans. 

The biggest of these is the Pacific Ocean, followed by the Atlantic Ocean. The Indian Ocean is between Asia and Africa, while the Arctic Ocean is in Arctic Circle, and the Southern Ocean is located around the South pole across the Antarctic circle. 

Actually, all the oceans run into one another to form one immense body of water, but scientists have divided them into different oceans and given them different names. Great ocean currents swirl around the Earth, some of them hundreds of kilometers long.

Winds cause the waves on the ocean's surface, while tides are caused by the gravitational pull of the Moon. The oceans provide a home for thousands of plants and animals, and they also regulate the Earth's weather and temperature.

 THE PACIFIC OCEAN

The Pacific is the biggest ocean on Earth, and covers more than 30 percent of the Earth's surface.

It is located between the Americas to the East and the Asian and Australian continents to the West. The Pacific is not only the biggest,but also the deepest ocean with the deepest trenches. The Challenger deep in the Marina Trench is the deepest point in the Pacific Ocean. It is 10,898 meters deep, and the lowest part of the Earth's crust.

The Pacific Ocean is home to 75% of the world's volcanoes. These volcanoes form a ring around the ocean basin and are known as 'The Ring of Fire'.

Most of the islands in the world are found in the Pacific Ocean. Some of these are islands made of coral, and are called atolls. In fact, the Pacific Ocean is famous for its coral reefs. The Great Barrier Reef in Australia is the largest reef in the world, stretching over more than 2,300 km.

A Spanish explorer named Balboa is believed to be the first European to discover the Pacific Ocean, on September 25th, 1513.

ATLANTIC OCEAN

The Atlantic Ocean is the world's second largest ocean.

The Atlantic is the second youngest among all the 5 oceans, and was formed when the super continent Pangea broke up. 

The Atlantic Ocean covers approximately 1/5th of the surface of the Earth, and covers approximately 20% of the Earth's surface.

There is an underwater mountain in the range in the North Atlantic Ocean called the Mid Atlantic Ridge. It is twice as wide as the Andes Mountain range and runs approximately 16093 kilometers south from Iceland.

The Atlantic Ocean is home to the second largest barrier reef in the world, the Belize barrier reef. Its natural resources include oil, fish, sand and gravel, natural gas, and precious stones.

Creatures living in the Atlantic Ocean include the manatee, humpback whale, sea lion and the grey Atlantic seal, as well as various shark and fish species. 

INDIAN OCEAN

The Indian Ocean is the world's third largest ocean. It covers 1/5th of the Earth's surface, connecting 18 Asian countries, 16 African countries, and 57 island groups.

The Kerguelen Plateau is a continent of volcanic origins that lies beneath of the surface of the Indian Ocean. The lowest part of this ocean is about 7,258 meters deep, lying on the Java Trench of the Sunda Shelf while its highest point is at the sea level.

The Indian Ocean is the warmest of the world's oceans, and is the source of approximately 40% of the world's oil.

The Indian Ocean is important for its ports that belong to different continents. Chennai, Mumbai, and Kolkata are the Indian ports of this ocean, while Colombo in Sri Lanka, and Durban in South Africa, Jakarta in Indonesia , and Melbourne in Australia are the other important ports of this ocean.

ARCTIC OCEAN

The Arctic Ocean is the smallest of all the oceans, and also the shallowest. It is connected to the Pacific and Atlantic Oceans through small gaps in the continents. It is a very cold ocean since it lies in the Arctic Circle.

Much of it is covered with a frozen ice cap. Three types of ice cover the Arctic Ocean including polar ice, fast ice, and pack ice. The ice located at the edge of the polar ice is called pack ice, which only freezes completely in the winter. Fast ice is the ice that forms during the winter around the pack ice, and on land around the Arctic Ocean . There is a wide variety of marine life living in the Arctic Ocean, including whales, fish , seals, and walruses. 

SOUTHERN OCEAN

The Southern Ocean is sometimes called the Antarctic Ocean. It surrounds Antarctica, and is the fourth largest of the 5 ocean of the world. Some scientists believe that the waters of the Southern Ocean are extensions of the India, Pacific, and Atlantic Oceans. 

The deepest part of the Southern Ocean is the southern end of the South Sandwich Trench that is 7235 meters deep. 

During winter, half of the Southern Ocean is covered in icebergs. Some of the ice and icebergs break off and float in the waters of the Southern Ocean. The world's largest penguin species the emperor penguin lives on the ice of the Southern Ocean and on the Antarctic continent. 

It is believed that if the ice sheets in the Southern Ocean were to melt the oceans around the world would rise by as much as 65 meters!!

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SUPERCONTINENTS

SUPER CONTINENTS

A Super continent is a continuous land mass made up of several continents. The Earth's outer shell is broken up into several plates called Tectonic plates.

Millions of years ago, the movement of these plates over the Earth's rocky shell or mantle, brought land masses into collision with each other.

                                            PANGEA 

The collision was so violent that mountains were formed as the existing continents smashed together to form one giant super continent. About 300 million years ago, during the time of the dinosaurs, Earth didn't have seven continents, but instead, one massive super continent called Pangea, which was surrounded by a single ocean called Panthalassa.

Later, Pangea started to break apart into two super continents. 

They were - GONDWANA and LAURASIA.

More mountains were formed, and parts of the continents that had been inland were now on the coast, and this changed the climate in many areas.

GONDWANA

Gondwana was an ancient super continent that was formed when Pangea broke up. About 280 million to 230 million years ago, Pangea started to split.

Magma from below the Earth's crust began pushing upward, creating a fissure between what would become AFRICA, SOUTH AMERICA, and NORTH AMERICA. 

As part of this process, Pangea cracked into a northernmost and southernmost super continent. The northern landmass came to be known as Lauraisa. The southern land mass headed southward after the split. The super continent was Gondwana. Gondwana stretched from the South pole to the Equator. 

However, the world was warmer then , and the climate was fairly mild. Gondwana had vast forests of temperate tress, with many dinosaurs, birds and reptiles running through the undergrowth.

Gondwana itself eventually split into the land masses we recognize today - AFRICA, SOUTH AMERICA , AUSTRALIA, ANTARCTICA, THE INDIAN SUBCONTINENT, and the ARABIAN PENINSULA.

 LAURASIA 

             

Laurasia is the name given to the largely northern super continent that is thought to have formed after the split of the Pangean super continent. It included most of today's continents in the northern hemisphere.

In fact, Lauraisa comprised of what later became North America and Eurasia, except for India. The super continent was dominated by conifers as well as other seed plants and ferns. 

At first, Laurasia was largely located in equatorial latitudes. Later, it began to break up, with North China and Siberia drifting into latitudes further north.The name Laurasia is a combination of the names of Laurentia and Eurasia. 

PANTHALASSA  

Panthalassa was the name given to the vast ocean that surrounded Pangea when that super continent was in existence.

In fact, the word Panthalassa means 'all the seas' . Currents in the Panthalassa would have been simple and slow, and the Earth's climate was, in all likelihood, warmer than today.

When Pangea broke up into Gondwana and Lauraisa. the Tethys seaway was formed. This sea seperated Gondwana from Laurasia. It became the home of many unique marine reptiles, mostly coastal an shallow water dwellers.

The breakup of Pangea also created the different oceans as we know them today - the PACIFIC, ATLANTIC, ARCTIC, INDIAN OCEAN, and SOUTHERN OCEANS.

WHAT IS CONTINENTAL DRIFT?

The term continental drift refers to a theory regarding the movements of continents that was first suggested by Abraham Ortelius in 1596.

However, it was developed into a proper theory only in 1912 by Alfred Wegener. 

According to this theory, the world was made up of a single continent millions and millions of years ago. That continent eventually separated and drifted apart, forming the seven continents that we have today. Wegener stated that the continents consist of lighter rocks that rest on the heavier material of the Earth's crust - similar to the manner in which icebergs float on water. 

He also believed that the relative positions of the continents are not rigidly fixed but are slowly moving - at a rate of about 1 yard per century. 

Today, the theory of continental drift has been replaced by the science of Plate Techtonics. 

WHAT IS PLATE TECHTONICS ?

Deep beneath the surface of the Earth, heat rises from the core, which is the center of the Earth, through the mantle, which is the next, and then it reaches the crust. It comes up slowly, but it actually moves the mantle.

The mantle rises beneath the Earth's crust before it spreads sideways, and then cools again. This slow, but constant movement of the mantle divides the Earth's crust into plates known as tectonic plates.

Most of the Earth is covered by 7 major plates and another eight or so minor plates. The seven major plates are the African, Antarctic, Eurasian, North American, South American, India - Australian, and the Pacific plates.

All this happens over millions of years, and it's called continental drift. The Earth only moves about 15 cm a year. The study of the movement of the plates on the Earth's crust is called plate tectonics.

WHAT IS THE PROOF OF CONTINENTAL DRIFT ?

 There is quite a lot of evidence to support the theory of continental drift. If you have noticed, the different continents are like pieces of a jigsaw puzzle that can be put together to give the picture of one huge land mass. Just look at the shapes of Africa, and South America on a map, and you can see this for yourself. 

Another point is that plant and animal fossils of the same age and similar species are found on the shores of different continents. This suggests that they were once joined. There is also living evidence, like the same unusual animals being found on different continents that are far apart. This provides further proof that Wegener was right in his theory !!!

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