Geography
The atmosphere is a layer of gas surrounding the Earth that is some 700 km (400 miles) thick. It is made up of nitrogen (78 per cent) and oxygen (21 per cent), plus traces of other gases. Tiny droplets of water vapour form the clouds we see.
Earth’s atmosphere is layered, and each layer of the atmosphere has its specific traits. The atmosphere of the Earth is divided into four layers: troposphere, Stratosphere, Mesosphere and Thermosphere, and they are separated based on temperature. Weather processes occur in the lower layers of the atmosphere while interesting events such as the beautiful aurora occur higher. By understanding how the atmosphere’s temperature changes with altitude, we can learn how the atmosphere works. In this article, let us familiarize ourselves with the layers of the atmosphere.
Structure of the Atmosphere
Unlike the changes in pressure and density, which decrease with altitude, the temperature changes are irregular. A change in temperature with distance is called a temperature gradient. The Earth’s atmosphere is divided into layers based on the layer’s temperature gradient, and the heat source of the layer determines the temperature gradient in each layer
Troposphere
Though the sunlight reaches the Earth’s surface from top to bottom, the troposphere is primarily heated at the bottom. The Earth’s surface is much better at absorbing a wide range of solar radiation than the air. When the parcel of warm air moves upwards, it expands, and when air expands, it cools. Due to this reason, the base of the troposphere is warmer than its base because the air on the surface of the Earth absorbs the sun’s energy, gets heated up, and moves upward, which cools down.
Stratosphere
The Stratosphere lies above the troposphere and extends up to a height of 50 km. This layer is free of clouds and devoid of any weather-related phenomenon. Due to this, aeroplanes fly in the Stratosphere for a smooth ride. The Stratosphere also houses the ozone layer that protects us from the harmful effect of the sun’s rays.
Mesosphere
The temperature in the mesosphere grows colder with the altitude. This is because there are few gas molecules in the mesosphere to absorb the Sun’s radiation. The only heat source is the stratosphere below. The mesosphere is extremely cold, especially at the top, dropping to a temperature as low as -90°C.
An astronaut travelling through the mesosphere would experience severe burns from the sun’s ultraviolet light because the ozone layer that provides UV protection is in the stratosphere below. Meteorites burn in this layer on entering the atmosphere from outer space
Thermosphere and Beyond
The density of molecules in the thermosphere is very low. One gas molecule can go about a distance of 1 km without colliding with another molecule. Because so little energy is transferred, the air feels freezing. Satellites are found orbiting in the upper part of the thermosphere.
Ionosphere
The ionosphere lies within the thermosphere. The ionosphere gets its name from the solar radiation that ionizes gas molecules to create a positively charged ion and one or more negatively charged electrons. These freed electrons travel within the ionosphere as electric currents. Due to these free ions, the ionosphere has many interesting characteristics. The aurora, the Northern Lights and Southern Lights, occur in the Earth’s ionosphere.
Exosphere
The exosphere is the final frontier of the Earth’s gaseous envelope. There is no clear-cut distinction between the Earth’s atmosphere layers and outer space. The air in the exosphere is constantly but gradually leaking out of the Earth’s atmosphere into outer space.
Oceans
The Global Ocean
The five oceans from smallest to largest are: the Arctic, Southern, Indian, Atlantic and Pacific.
If you were to add the smaller seas like the Barents, Beaufort, Chukchi, Kara, Laptev, East Siberian, Lincoln, Wandel, Greenland and Norwegian, etc. you would have a total area of the ocean of about 361,000,000 km² (which is ~71% of the Earth’s surface), a total volume of roughly 1,370,000,000 km³, and an average depth of 3,790 m. Our hydrosphere (ocean plus all freshwater in ground water, lakes, rivers, snow, ice and the atmosphere) makes up about 0.023% of the total mass of the Earth
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Ocean Geography
The five oceans are connected and are actually one huge body of water, called the global ocean or just the ocean.
The Global Ocean
The five oceans from smallest to largest are: the Arctic, Southern, Indian, Atlantic and Pacific.
oceans
If you were to add the smaller seas like the Barents, Beaufort, Chukchi, Kara, Laptev, East Siberian, Lincoln, Wandel, Greenland and Norwegian, etc. you would have a total area of the ocean of about 361,000,000 km² (which is ~71% of the Earth’s surface), a total volume of roughly 1,370,000,000 km³, and an average depth of 3,790 m. Our hydrosphere (ocean plus all freshwater in ground water, lakes, rivers, snow, ice and the atmosphere) makes up about 0.023% of the total mass of the Earth.
The Water Cycle
The word “Ocean” comes from Okeanos, the Greek god of the Ocean.
Global gravity map
Terrigenous, pelagic, and authigenic materials composes most of ocean sediments. Erosion, weathering and volcanic activity on land washes out to sea and creates the sand, mud, and rock particles that make up terrigenous deposits. Consequently, terrigenous deposits are confined to narrow marginal bands close to land like continental shelves and are deepest near the mouths of large rivers or desert coasts. Pelagic deposits derived from seawater are red clays and the skeletal remains of organisms that have died and sunk to the ocean floor. These include pelagic red clays and globigerina, pteropod and siliceous oozes. Most of the ocean floor is actually covered in these organic remains with a depth ranging anywhere from 60 to 3,300 m deep, but they are thickest in convergence belts and upwelling zones. Authigenic deposits are made up of particles like manganese nodules and include montmorillonite and phillipsite and can be found in places where the sedimentation process occurs very slowly or currents sort out the deposits.
The Arctic Ocean
The Arctic Ocean is divided by an underwater ocean ridge called the Lomonosov ridge into the 4,000-4,500 m deep Eurasian or Nasin basin and the 4,000 m deep North American or Hyperborean basin. The topography of the Arctic Ocean bottom varies consisting of fault-block ridges, abyssal plains, and ocean deeps and basins that have an average depth of 1,038 m due to the continental shelf on the Eurasian side.
The greatest inflow of water to the Arctic Ocean comes from the Atlantic via the Norwegian Current, (which then travels along the Eurasian coast) although water also enters from the Pacific via the Bering Strait. The greatest outflow comes from the East Greenland Current. Ice used to cover most of the Arctic Ocean year round (this is now changing drastically due to global warming). When the ice melts, salinity and subfreezing temperatures vary. The subfreezing temperatures cool the air traveling towards the equator, mixing with warmer air at middle latitudes, resulting in rain and snow. Marine life is thought to be relatively scarce in the cold waters of the Arctic Ocean except in the open, southerly waters. Air traffic is common over the Arctic because it is the shortest route between the Pacific coast of North America and Europe. For boats, major ports are the Russian cities known as Murmansk and Arkhangelsk (Archangel).
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