Oceans and Atmosphere

What do you mean by the atmosphere?

The word atmosphere comes from two Greek words atmós and sphaîra meaning vapour and sphere respectively. The atmosphere is a layer of gases that cover the earth and is held together by gravity. The atmosphere of Earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and little amounts of other gases as well. 

Evolution of atmosphere:

Around 4.5 billion years ago the earth had little or no atmosphere, the minimum amount of atmosphere that formed was made up of hydrogen and helium which were moving fast because of the hot atmosphere and they escaped the earth’s gravity and drifted into space. When the earth’s crust was forming it had a lot of volcanoes that frequently erupted and disturbed the atmosphere. They released steam (H2O), carbon dioxide (CO2), ammonia (NH3) into the atmosphere. Carbon dioxide is dissolved in seawater. Simple bacteria thrived on sunlight and CO2. Thus, releasing oxygen (O2) as a byproduct.

Currently, the present atmosphere was formed when the volcanoes stopped erupting and the earth’s temperature cooled down considerably. The oxygen began to build up in the atmosphere, while the carbon dioxide levels continued to drop. Meanwhile, the ammonia molecules in the atmosphere were broken apart by sunlight, leaving nitrogen and hydrogen. The hydrogen, being the lightest element, rose to the top of the atmosphere and much of it eventually drifted off into space.

Importance of atmosphere:

1.  The atmosphere acts as a temperature regulator of the earth, the greenhouse gases present in the atmosphere trap heat inside the atmosphere which in turn maintains the temperature of the earth otherwise the earth would be freezing at night and baking in the daytime.
2. The atmosphere contains two of the most essential gases that are responsible for it i.e., oxygen and carbon dioxide, both of these gases play a vital role in photosynthesis which is an extremely important life process in plants and since animals are dependent on plants for food so they also rely on the atmosphere. 
3. The atmosphere also has ozone(O3) which absorbs high-energy ultraviolet (UV) radiation coming from the Sun. This protects living things on Earth’s surface from the Sun’s most harmful rays. Without ozone for protection, only the simplest life forms would be able to live on Earth.

Layers of the atmosphere:

The atmosphere consists of 5 layers namely:

1. troposphere
2.  stratosphere
3. mesosphere
4. thermosphere
5. exosphere

 1. The troposphere (between 0 and about 15 kilometres) is the first layer above the Earth’s surface and contains approximately 85 to 90 % of the mass of the Earth’s atmosphere. It is characterised by decreasing temperature with increasing altitude.

2. The Stratosphere is very dry with rare formation of clouds; it has ozone gas and aeroplanes fly in this layer because of its stability. Here the temperature tends to increase with elevation.

3. In this layer meteors start burning when they crash on the earth, here temperatures are the lowest in the atmosphere. The top mesosphere is called mesopause.

4. The thermosphere is home to those beautiful celestial light shows known as auroras. The thermosphere varies wildly in temperature. It can go from really cold to as hot as about 1,980 ºC near the top. The sun’s varying energy output also causes the thickness of this layer to expand as it heats and to contract as it cools. The layer’s top boundary is called the thermopause.

5. The exosphere has no defined top, the air molecules here are so wide apart that they do not collide with each other, its lower boundary is called exobase.

What are oceans?

The word ocean is derived from the Greek word ōkeanos which means great stream encircling the earth’s disc. It is a body of water that has salt in it. It covers approximately 70% of the earth and it constitutes 97% of the water available on the earth.

Formation of an ocean:

Earth just after forming was a hot planet; it had no atmosphere, no ocean and no life. Millions of years later the earth cooled down and the atmosphere started forming, volcanoes erupted hence releasing H2O or water vapour in the atmosphere, while the meteors that were crashing down on earth brought in more water. The presence of water vapour in the atmosphere made it rain for centuries on earth, hence cooling the temperatures significantly for the formation of oceans.

Oceans in the world:

There are 5 oceans in the world namely:

1.  Pacific Ocean 
2. Atlantic Ocean 
3. Indian Ocean 
4. Southern Ocean 
5. Arctic Ocean

1.The Pacific Ocean is the largest ocean in the world in terms of area and volume it covers approximately 47% of the area and 50% of the volume. It is present between Asia, Australasia and Americas, its deepest point is Mariana Trench which is also the deepest point on earth.

2. The Atlantic Ocean covers nearly 24% of the area and an equal percentage in terms of volume. It occupies an elongated, S-shaped basin extending longitudinally between Europe and Africa to the east, and the Americas to the west. It is the second largest ocean in the world.

3. The Indian Ocean is bounded by Asia to the north, Africa to the west and Australia to the east. Locally it is known as Hind Mahasagar or Indic Ocean. The Chinese explorers who came into India in the 15th century named it the Indian Ocean.

4. It is also called Antarctic Ocean, it is present between Antarctica and the Pacific, Atlantic and Indian oceans. Over the past 30 years, it has been subjected to climate change that has led to changes in its marine ecosystems

5. The Arctic Ocean is the smallest and shallowest of the world’s five major oceans. It is the coldest of all the oceans. It is present between northern North America and Eurasia in the Arctic. It spans an area of approximately 14,060,000 km2.

Conclusion:

Through this article, we got to know in detail about the atmosphere and the oceans across the world. We got to know meaning, formation, uses, layers of atmosphere and meaning, formation and types of oceans in the world. This article told us how both the oceans and the atmosphere are essential for living organisms and without any living organisms would not survive.