Earth Science: Structure Of the Atmosphere

Discovery Science: Earth – Atmosphere

The atmosphere is the gaseous envelope that protects the Earth against dangerous radiation from space and enables the development and existence of life on our planet.

Its formation took several billion years, but information about its structure and internal processes has only been accumulated over recent decades.

Earth Science: Structure Of the Atmosphere

The current atmosphere is the fourth in Earth’s history. It consists of 78 percent nitrogen, 21 percent oxygen, and various amounts of noble gases, carbon dioxide, water vapor, and nitrogenous and sulfurous compounds.

The approximately 63-mile (100-km) thick atmosphere of the Earth is merely a thin layer, relative to the Earth’s diameter of 7,926 miles (12,756 km) at the Equator. The percentage of gaseous parts varies depending on altitude, and the air pressure decreases with increasing altitude, enabling the atmosphere to be categorized as distinct vertical layers. The layer closest to the Earth is the troposphere, where practically all weather occurs. It contains more than 90 percent air and most of the water vapor in the atmosphere.

At the Poles, this layer is up to 4.5 miles (7 km) high, while along the Equator it can reach up to 1 1 miles (18 km). The temperature of the tropo- sphere decreases toward the upper boundary (tropo- pause) at a rate of about 50.8T per mile (6.5°C/km). In the next layer, the stratosphere, the temperature increases from -140°F (-96°C) to about 32°F (0°C) at the 31 -mile (50-km)-high upper boundary. This change is brought about by the warming of the ozone layer as it absorbs ultraviolet radiation.

The temperature decreases again in the mesosphere. At its upper boundary (mesopause) the temperature is about -130°F (-90°C) and its lower boundary of the polar lights (aurora borealis and aurora australis). In the 124-mile (200-km)-high thermosphere the few gaseous particles located in the upper thermosphere can reach over 1832°F (1000°C).

The last layer is the exosphere, at an altitude of about 621 miles (1,000 km). Outside the atmosphere, the Earth is surrounded by energy-rich particulate radiation (Van Allen The atmosphere is divided into layers that vary in chemical composition and temperature. belt). Structuring the atmosphere by gaseous electrical charge, three extra categories emerge. The neutrosphere extends up to 50 miles (80 km), becoming the ionosphere and then blending into the protonosphere toward outer space.

Structuring the atmosphere based on composition, we also get the homosphere, where all gaseous components are mixed equally, and the heterosphere, where the gas mixture separates because of the diminishing attraction from the Earth.


POLAR LIGHTS are caused by charged particles from the sun, which are diverted by the magnetic field of the Earth to the polar regions.

There, the particles collide with oxygen and nitrogen atoms in the upper atmosphere, creating the visible effect of colored light.