The AtmosphereThe Atmosphere

Chapter 26 page 641Chapter 26 page 641

First atmosphereFirst atmosphere

The first atmosphere was probably The first atmosphere was probably H and He H and He

This was when the sun was still a This was when the sun was still a protostarprotostar

When it became a star the initial When it became a star the initial blast probably blew away the blast probably blew away the atmosphereatmosphere

Composition of Composition of atmosphereatmosphere

Different now than Different now than early earth. Why?early earth. Why?

Early atmosphere Early atmosphere came from out came from out gassing of gassing of volcanoes.volcanoes.

Early earth COEarly earth CO22 and and water vapor. water vapor.

Remember it was a Remember it was a very hot place. very hot place.

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

To get our present To get our present atmosphere we needed atmosphere we needed oxygen.oxygen.

How do we get it?How do we get it? Plants: Plants: StromatolitesStromatolites and algae at and algae at

firstfirst PhotosynthesisPhotosynthesis HH220 + CO0 + CO2 2 + light + light CC66HH1212OO66 + O + O22

With the production of oxygen, OWith the production of oxygen, O2, 2,

we could have ozone (Owe could have ozone (O33).).

Filters out UV Filters out UV lightlight

Composition of Composition of AtmosphereAtmosphere

KNOW 1KNOW 1stst 2 2 Nitrogen 78% Nitrogen 78%

Oxygen 21%Oxygen 21% ArgonArgon Neon, helium, Neon, helium,

hydrogen, hydrogen, methanemethane

HH22O vaporO vapor

COCO2 2

Structure of the Structure of the AtmosphereAtmosphere

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

tropospheretroposphere- - ground to 16kmground to 16km

The The tropospheretroposphere is is the first layer above the first layer above the surface and the surface and contains half of the contains half of the earth's atmosphere.earth's atmosphere.

WeatherWeather occurs in occurs in this layer. this layer.

Warmest near Warmest near ground, cools as ground, cools as you go upyou go up

StratosphereStratosphere 16km- 16km-50km50km

UV absorbed by UV absorbed by ozoneozone in the in the stratospherestratosphere

-50-50 at bottom to 0 at bottom to 0C at topC at top Many jet aircraft fly in the Many jet aircraft fly in the

stratosphere stratosphere because it is very because it is very stablestable

MesosphereMesosphere 50-80km 50-80km

gases absorb little Egases absorb little E 00C at bottom to -90C at bottom to -90C at topC at top Meteors burn up in the Meteors burn up in the

mesosphere.mesosphere.

ThermosphereThermosphere

Very little air but, Very little air but, reaches 2000reaches 2000C--C--hothot

The The thermosphere thermosphere is a layer with is a layer with auroras, meteors auroras, meteors and where the and where the space shuttle orbitsspace shuttle orbits

IonosphereIonosphere Layer within the Layer within the

thermosphere and thermosphere and upper mesosphereupper mesosphere Ion rich charged Ion rich charged particlesparticles

Atmospheric OAtmospheric O22 and and NN22 are stripped of are stripped of electrons by solar electrons by solar radiationradiation reflects radio signalsreflects radio signals Aurora borealis-Aurora borealis-

northern lightsnorthern lights

ExosphereExosphere

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

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

Magnetic fieldMagnetic field

Protects us Protects us from the solar from the solar windwind

Remember the Remember the effects shown effects shown in in The CoreThe Core

TemperaturesTemperatures

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

Pressure decreases

The source of this material is The source of this material is Windows to the UniverseWindows to the Universe, at , at http://www.windows.ucar.edu/http://www.windows.ucar.edu/ at the at the University Corporation for University Corporation for Atmospheric Research (UCAR). Atmospheric Research (UCAR). ©1995-1999, 2000 The Regents of ©1995-1999, 2000 The Regents of the University of Michigan; ©2000-02 the University of Michigan; ©2000-02 University Corporation for University Corporation for Atmospheric Research. All Rights Atmospheric Research. All Rights Reserved.Reserved.