Atmosphere Evolution Atmosphere = The layer of gases that surround the Earth Earth’s atmosphere traps the sun’s energy to: Keep Earth at a livable temperature Allows water to exist as a liquid Why is this layer important? It provides all the necessary gases (plus water) living things need to survive.

Atmosphere Evolution The Earth’s atmosphere has not always been like it is today. Very first atmosphere: Composed of hydrogen and helium, trace amounts of ammonia and methane, no O2. Left over from the solar system formation. (Stars are mostly Hydrogen and Helium) As Earth formed, its gravity pulled the gases close. Birth of sun/solar flare swept early atmosphere away.

Atmosphere Evolution 2nd Atmosphere formation: Gases from inside Earth escaped through volcanoes and fissures in Earth’s surface.

Atmosphere Evolution

Atmosphere Evolution Second atmosphere Gases composed of 85% water vapor, 10% carbon dioxide, & 5% nitrogen. Still had no free oxygen. Very hot during this Precambrian time. Why?

Atmosphere Evolution Next stage: Free oxygen is produced by primitive plants (stromatolites and green algae) by the process of photosynthesis.

Atmosphere Evolution Free oxygen results in an ozone (O3) forming in upper atmosphere.

Atmosphere Evolution Ozone layer acts as a filter to reduce amount of UV radiation reaching Earth’s surface.

Atmosphere Evolution Next: As Earth cools, water vapor condensed to start forming oceans.

Atmosphere Evolution Meteors and comets add water to oceans. In some cases, one drop at a time.

Earth’s Atmosphere Composition of Current Atmosphere: 78% Nitrogen 21% Oxygen 0.9% Argon Less than 0.1% total of Ne, He, methane, and H2 Variable (changing gases) include: water vapor, carbon dioxide, ozone, sulfur dioxide, and nitrogen dioxide.

Structure of the Atmosphere Troposphere: Lowest layer – between 8-16 Km above the surface Thinnest layer, but contains 90% of the atmosphere’s mass Almost all clouds and water vapor Top portion reaches -50º C

Structure of the Atmosphere

Structure of the Atmosphere Stratosphere: From 8-16 Km to 50 Km above Earth Radiation absorbed from ozone here Temps go from -50°C at the bottom of this layer to 0º C at the top

Structure of the Atmosphere

Structure of the Atmosphere Mesosphere: From 50 Km to 80 Km above the surface of the Earth 0° C at the bottom and -90º C at the top Most meteors burn up in this layer

Structure of the Atmosphere

Structure of the Atmosphere Thermosphere: From 80 Km above the earth to 500 Km Very little air up here Auroras generally happen in this layer or the upper mesosphere

Structure of the Atmosphere

Structure of the Atmosphere Ionosphere: Area within the upper mesosphere and thermosphere Place with a large number of ions that were stripped from O2 and N2 by high frequency solar radiation Auroras or Northern Lights

37.2 Structure of the Atmosphere

Structure of the Atmosphere Exosphere: Above 500 Km above the Earth Thinning atmosphere turns into the radiation belts and magnetic fields of space

Atmosphere Interaction The atmosphere interacts with the geosphere (land) in 2 ways: It protects the land from meteors that usually burn up in the mesosphere. It creates weather that leads to the weathering, erosion , and deposition of sediment. The Troposphere (lowest layer) is the layer in which all weather occurs

Atmosphere Interaction Weather – The condition of the Earth’s atmosphere at particular time and place. Weather causes changes to the geosphere (land) due to weathering and erosion. Hard rain and rapid temperature changes can cause mechanical and chemical weathering. Sediment is then moved (eroded) and placed in a different location, altering the geosphere

Atmosphere Interaction The atmosphere interacts with the hydrosphere(water) because it controls how much heat is applied to different parts of the Earth. How much heat is applied to a spot can affect how much ocean evaporation or glacial melting goes on. So, why do we care?

Atmosphere Interaction Extra evaporation increases the salinity of the ocean. Extra glacial melting decreases the salinity of the ocean. These salinity changes change the ocean currents and what temperature water goes where. This will then turn around and affect the atmosphere and weather above or near these ocean currents.