The Atmosphere Chapter 26 page 641

First atmosphere The first atmosphere was probably H and He The first atmosphere was probably H and He This was when the sun was still a protostar This was when the sun was still a protostar When it became a star the initial blast probably blew away the atmosphere When it became a star the initial blast probably blew away the atmosphere

Composition of atmosphere Different now than early earth. Why? Early atmosphere came from out gassing of volcanoes. Early earth CO 2 and water vapor. Remember it was a very hot place.

After condensation of water vapor produced the earth's oceans, they swept out the carbon dioxide and locked it up into rocks, our atmosphere was mostly nitrogen. After condensation of water vapor produced the earth's oceans, they swept out the carbon dioxide and locked it up into rocks, our atmosphere was mostly nitrogen.

To get our present atmosphere we needed oxygen. How do we get it? How do we get it? Plants: Stromatolites and algae at first Plants: Stromatolites and algae at firstStromatolites Photosynthesis Photosynthesis H CO 2 + light C 6 H 12 O 6 + O 2 H CO 2 + light C 6 H 12 O 6 + O 2

With the production of oxygen, O 2, we could have ozone (O 3 ). Filters out UV light

Composition of Atmosphere KNOW 1 st 2 Nitrogen 78% Oxygen 21% Nitrogen 78% Oxygen 21% Argon Argon Neon, helium, hydrogen, methane Neon, helium, hydrogen, methane H 2 O vapor H 2 O vapor CO 2 CO 2

Structure of the Atmosphere The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space.

troposphere- ground to 16km The troposphere is the first layer above the surface and contains half of the earth's atmosphere. The troposphere is the first layer above the surface and contains half of the earth's atmosphere. Weather occurs in this layer. Weather occurs in this layer. Warmest near ground, cools as you go up Warmest near ground, cools as you go up

Stratosphere 16km-50km UV absorbed by ozone in the stratosphere UV absorbed by ozone in the stratosphere -50  at bottom to 0  C at top -50  at bottom to 0  C at top Many jet aircraft fly in the stratosphere because it is very stable Many jet aircraft fly in the stratosphere because it is very stable

Mesosphere 50-80km gases absorb little E gases absorb little E 0  C at bottom to -90  C at top 0  C at bottom to -90  C at top Meteors burn up in the mesosphere. Meteors burn up in the mesosphere.

Thermosphere Very little air but, reaches 2000  C--hot The thermosphere is a layer with auroras, meteors and where the space shuttle orbits

Ionosphere Layer within the thermosphere and upper mesosphere Ion rich charged particles Layer within the thermosphere and upper mesosphere Ion rich charged particles Atmospheric O 2 and N 2 are stripped of electrons by solar radiation Atmospheric O 2 and N 2 are stripped of electrons by solar radiation reflects radio signals reflects radio signals Aurora borealis-northern lights Aurora borealis-northern lights

Exosphere The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.

After this there are radiation belts and magnetic fields of interplanetary space

Magnetic field Protects us from the solar wind Remember the effects shown in The Core

Temperatures This image shows the average temperature profile through the Earth's atmosphere. Temperatures in the thermosphere are very sensitive to solar activity and can vary from 500°C to 1500°C. This image shows the average temperature profile through the Earth's atmosphere. Temperatures in the thermosphere are very sensitive to solar activity and can vary from 500°C to 1500°C.

Pressure decreasesPressure decreases

The source of this material is Windows to the Universe, at at the University Corporation for Atmospheric Research (UCAR). © , 2000 The Regents of the University of Michigan; © University Corporation for Atmospheric Research. All Rights Reserved. The source of this material is Windows to the Universe, at at the University Corporation for Atmospheric Research (UCAR). © , 2000 The Regents of the University of Michigan; © University Corporation for Atmospheric Research. All Rights Reserved.