Atmosphere of Earth

Our beautiful earth is the only planet in the solar system which has an atmosphere in which life can exist. The gases in the atmosphere protect us from heat, radiation and dangerous rays from the sun as well as it provides us sufficient air to breath. Our atmosphere contains water vapors  traces of dust particles, pollen, plant grains and many other solid particles.  From the past century, air pollution and many dangerous gases such as greenhouse are destroying our atmosphere. It has severe impact on the atmosphere, they are causing changes like Acid rain, holes in the ozone layer, Global warming etc etc.

Composition: Earth's atmosphere is a think layer of gases. Which are composed of 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and trace amount of other gases. There is no exact place where the atmosphere ends; it just gets thinner and thinner, until it merges with outer space. 

Layers: There are five main layers of Earth’s atmosphere. Which are Troposphere, Stratosphere, Mesosphere, Ionosphere and Exosphere. As mentioned above, there no end to atmosphere but we do have an imaginary line of about 110 Km from the surface and it’s called Karman line. Scientists say that our atmosphere meets outer space at Karman line. Let’s read each layer in brief:

Troposphere: This layer is the closest one to Earth. It is 4 – 12 miles (7 – 20 km) thick and contains almost half of Earth’s atmosphere. We find clouds in this sphere because almost all the dust and water vapors are in this sphere. In the troposphere, the temperature generally decreases as altitude increases.

Stratosphere: It is the second layer and ends about 50 km above ground. This is the layer where jet aircrafts and weather balloons fly. Ozone is abundant here and it heats the atmosphere while also absorbing harmful radiation from the sun. Only the highest clouds (cirrus, cirrostratus, and cirrocumulus) are in the lower stratosphere.

Mesosphere: It starts at 31 miles (50 km) and extends to 53 miles (85 km) high. The top of the mesosphere, called the mesopause, is the coldest part of Earth's atmosphere with temperatures averaging about minus 130 degrees F (minus 90 C). This layer is hard to study. Jets and balloons don't go high enough, and satellites and space shuttles orbit too high. Scientists do know that meteors burn up in this layer.

Thermosphere: It extends from about 56 miles (90 km) to between 310 and 620 miles (500 and 1,000 km). Temperatures can get up to 2,700 degrees F (1,500 C) at this altitude. The thermosphere is considered part of Earth's atmosphere, but air density is so low that most of this layer is what is normally thought of as outer space. In fact, this is where the space shuttles flew and where the International Space Station orbits Earth.

Exosphere: This is the highest layer, is extremely thin and is where the atmosphere merges into outer space. It is composed of very widely dispersed particles of hydrogen and helium.

Earth is only Planet with Tectonic Plates !

Our Earth is unique in many ways. One of them is that our Earth is the only planet which has active plate tectonics. Earth crust floats on thick liquid rock of the mantle below. The crust then breaks in to various parts and we call them plates. These are the plates which cause earth quakes, volcanoes as they interact. So, Plate boundaries are place where plates meet. Talking about the plate boundary, there are three types: constructive, destructive ad transform. 

Layers of Earth

Earth has multiple layers. The ocean basins and the continents compose the crust, the outermost layer. Earth's crust is between three and 46 miles (five and 75 km) deep. The thickest parts are under the continents and the thinnest parts are under the oceans.

Earth has multiple layers: the crust, mantle and core.
                   Credit: NASA

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Crust

Earth's crust is made up of several elements: iron, 32 percent; oxygen, 30 percent; silicon, 15 percent; magnesium, 14 percent; sulfur, 3 percent; nickel, 2 percent; and trace amounts of calcium, aluminum and other elements.

The crust is divided into huge plates that float on the mantle, the next layer. The plates are constantly in motion; they move at about the same rate as fingernails grow. Earthquakes occur when these plates grind against each other. Mountains form when the plates collide and deep trenches form when one plate slides under another plate. Plate tectonics is the theory explaining the motion of these plates.

Mantle

The mantle under the crust is about 1,800 miles deep (2,890 km). It is composed mostly of silicate rocks rich in magnesium and iron. Intense heat causes the rocks to rise. They then cool and sink back down to the core. This convection — like a lava lamp — is believed to be what causes the tectonic plates to move. When the mantle pushes through the crust, volcanoes erupt.

Core

At the center of the Earth is the core, which has two parts. The solid, inner core of iron has a radius of about 760 miles (about 1,220 km). It is surrounded by a liquid, outer core composed of a nickel-iron alloy. It is about 1,355 miles (2,180 km) thick. The inner core spins at a different speed than the rest of the planet. This is thought to cause Earth's magnetic field. When charged particles from the solar wind collide with air molecules above Earth's magnetic poles, it causes the air molecules to glow, causing the auroras.

Sources : http://www.space.com

Earth is not Round in Shape

Our Earth is not round, as many of us being told by our elders. In fact, our Earth is not a perfect sphere due to its gravitational pull. It is not a sphere, but kind of pear-shaped. The real shape of the Earth is called 'Oblate Spheroid'. Where Oblate means 'slightly oblong appearance' and Spheroid means 'almost sphere', but not exactly for sure. The diameter from the North Pole to the South Pole (the shortest diameter) is approximately 12,714 km. The equatorial diameter (the longest diameter) is approximately 12,756 km. This is not a big difference, but it does make the Earth not quite a sphere.