EARTH AND ATMOSPHERE

EARTH AND ATMOSPHERE

 

 

                  Long ago, people used to think the Earth was flat. They believed if they sailed a boat far out into the ocean, the boat would fall off the Earth! Now people know that this is not true. We know the Earth is not flat. It is shaped like a ball. The Earth only looks flat to us because it is so large. We can only see a small part of the Earth's surface when we are standing on it.

Inside the earth 

                       The interior structure of the Earth is layered in spherical shells, like an onion. According to scientific studies, the earth from the top to center can be divided into three parts:  Crust, Mantle and  the Core. Core further subdivided into outer core and inner core.

Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. The outer skin of the earth is called crust. The crust of the Earth is like the skin of a peach. The skin on the peach is very thin. It is only a small part of the peach. The crust of the Earth is also very thin. It is only a small part of the Earth. The crust is the Earth's thinnest layer. The crust is composed mainly of basalt and granite and, with the uppermost part of the upper mantle, is broken into tectonic plates. The crust is cooler and more rigid than the deeper layers. The thickness of the crust varies considerably.  The thickness  of the  crust varies  from 5 to 10  km  under the  oceans  and continents  the crust is made up of three kinds of rocks -  igneous sedimentary and metamorphic .Beneath the earth’s crust are the mantle, the earth’s   the  mantle is a thick  layer of solid rocks and goes down to about 2900 km. The rocks in the mantle are made up of silicon, oxygen, aluminum, iron and magnesium its temperature increases from 870c to2200c as we go down. The outer core is about 2200 km thick and is made of melted iron and nickel. Its temperature ranges from 2200 C(upper most part) to 5000 C (deepest part). The ball shaped inner core is about 5150 km below the earth’s surface. The centre of the inner core is about 1200km below the inner boundary of outer core. It is made of solid iron and nickel.

                The large zone corresponding to the flesh of the peach is called the "mantle." It is made mostly of rocky minerals with names like olivine, pyroxene, quartz, and periclase. (Any good book on geology or mineralogy will tell you everything you ever wanted to know about these minerals.) Almost all rocks are made of silicon and oxygen mixed with other elements, such as calcium, aluminum, and iron. Mantle rock contains particularly large amounts of iron and magnesium. The mantle is also divided into two solid parts, the lower mantle and the upper mantle. This division in the mantle may be due to small differences in the amounts of iron and magnesium or to differences in the nearness of atoms to each other. (As an analog, think of a piece of Styrofoam. 

    Atmosphere

                The earth is surrounded by the atmosphere, which is the body of air or gasses that protects the planet and enables life. Most of our atmosphere is located close to the earth's surface where it is most dense. The air of our planet is 79% nitrogen and just under 21% oxygen; the small amount remaining is composed of carbon dioxide and other gasses. There are five distinct layers of the earth. Let's look at each, from closest to farthest from the earth.

                The layer of the atmosphere closest to the earth is the troposphere. This layer is where weather occurs. It begins at the surface of the earth and extends out to about 4-12 miles. The temperature of the troposphere decreases with height. This layer is known as the lower atmosphere.

      The envelope of air which surrounds the earth from all sides is called atmosphere is held due to the gravitational pull of the earth. The Earth's atmosphere is more than just the air we breathe. It's also a buffer that keeps us from being peppered by meteorites, a screen against deadly radiation, and the reason radio waves can be bounced for long distances around the planet.  The outer layer of the atmosphere is called exosphere which extended up to an altitude of 2000km above the sea level.

   All gases of the atmosphere combined together constitute air. Atmosphere contains 78%nitrogen, 21% oxygen and remaining 1 % consists of argon, carbon dioxide, neon, helium, ozone and hydrogen. Air also contains water vapor and particles of dust.  In the lower layer of the atmosphere, the ratio of different gases remains relatively constant but the percentage of water vapor goes on changing. Clouds float in the lowest part of the atmosphere called troposphere. The air gets thinner, as we go above the surface of the earth. The lowest is the troposphere, which is the layer that provides most of our weather. It contains about four-fifths of the Earth's air, but extends only to a height of about 11 miles (17 kilometers) at the Equator and somewhat less at the Poles. The name comes from a Greek word that refers to mixing. And mixing is exactly what happens within the troposphere, as warm air rises to form clouds, rain falls, and winds stir the lands below. Typically, the higher you go in the troposphere, the colder it gets. Above the troposphere is the stratosphere. It extends to a height of about 30 miles (50 kilometers) and includes the ozone layer, which blocks much of the sun's harmful ultraviolet rays. The stratosphere is warmer than the troposphere because of the energy from the ultraviolet light absorbed by the ozone. At its base, the stratosphere is extremely cold, about -110 degrees Fahrenheit (-80 degrees Celsius). At its top, the temperature has risen back nearly to freezing. Next comes the mesosphere. In this layer, the air temperature drops again, down to nearly -180 degrees Fahrenheit (-120 degrees Celsius) at the top. Meteors generally burn up in the mesosphere, which extends to a height of about 52 miles (85 kilometers). This is why the Earth's surface isn't pocked with meteor craters, like the moons.