Topic 1d - Unravelling the complex structure of the Atmosphere

The majority of Earth’s atmosphere is comprised of Nitrogen (78%) and Oxygen (21%), followed by Argon (0.9%). The atmosphere extending upwards 600 km, is divided into four regions of positive and negative temperature gradient. These regions are the Troposphere, the Stratosphere, Mesosphere, and Thermosphere. The ozone layer is located in the Stratosphere, which extends to 50 km high. The Thermosphere extends to 600 km and this is where many satellites can be found. After these four regions is the Exosphere, here the atmosphere is incredibly thin, and the layer gradually gives way to deep space. Satellites can also be in this layer.

The Stratosphere has a positive temperature gradient and oxygen (O2) concentrations increase rapidly towards lower altitudes. In this layer chemical reactions involving solar ultraviolet radiation (sunlight) and oxygen molecules take place, forming ozone (O3).
In the troposphere there is a negative temperature gradient. Here the constituents (gas and aerosols) are constantly being mixed and changing. The natural sources of atmospheric constituents include direct release from the biosphere, exchange at the surface, lightning, natural fires, and stratospheric-tropospheric exchange. However anthropogenic activity, such as biomass burning and fossil fuels is modifying tropospheric chemistry.

Featured Educators:

  • Prof. Paul Monks

  • Prof. John Remedios

  • Dr Vincent-Henri Peuch

Don’t forget you can download the video, transcript and take any quizzes available with the links on the right.

Optional Further Reading


Ionosphere and airglow

The ionosphere is a layer of charged particles in Earth’s atmosphere that extends from about 50 to 360 miles above the surface of Earth. Processes in the ionosphere also create bright swaths of colour in the sky, known as airglow.

Earth’s Horizon and the Moon

This image was taken aboard the ISS in 2005, showing the Earth’s horizon, Atmospheric layers and the Moon

Layers of the Atmosphere

Diagram showing the layers in the atmosphere, their heights and what can be found in each one.

Thin Blue Line

Photograph of Earth’s atmosphere and the setting sun, taken by the crew of the International Space Station