First+Period

[|Fact about the Earth's Atmosphere] [|Earths Atmosphere2] [|Earths Atmosphere]

__Earth's Subsystems__ The Earth System is composed of four subsystems : earth (geosphere), water (hydrosphere ), air (atmosphere) , and life (biosphere). The geosphere (the earth subsystem) was formed very early in Earth's history through accretion of planetisimals. The hydrosphere (the water subsystem) formed early in Earth's history, probably from the outgassing of water trapped in the planetisimals that accreted to form the Earth. The hydrosphere (the water subsystem) formed early in Earth's history, probably from the outgassing of water trapped in the planetisimals that accreted to form the Earth. The life subsystem began with the appearance of the first living things. This apparently occurres very early in Earth's history, before 3.5 BYA and perhaps as early as 3.8 billion years ago, which would be very shortly after the formation of the solid crust and the appearance of the oceans.



media type="custom" key="5920677" Video about the layers of the atmosphere.

The atmosphere is divided into 5 layers. The troposphere is the first layer, and this is where weather occurs. The depth of this layer varies from about 8 to 16 kilometers. Greatest depths occur at the tropics where warm temperatures cause vertical expansion of the lower atmosphere. The Stratosphere is the next layer; this is where many jet aircrafts fly. This layer extends from an average altitude of 11 to 50 kilometers above the Earth's surface. This stratosphere contains about 19.9 % of the total mass found in the atmosphere. Very little weather occurs in the stratosphere. The mesosphere is the middle layer in the mesosphere; the atmosphere reaches its coldest temperatures (​about -90° Celsius) at a height of approximately 80 kilometers. The last atmospheric layer has an altitude greater than 80 kilometers and is called the thermosphere. Temperatures in this layer can be as high as 1200°C. These high temperatures are generated from the absorption of intense solar radiation by oxygen molecules (O2). The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.