The Atmosphere Chapter 22 page 546

First atmosphere WS 25 points The first atmosphere was probably H and He This was when the sun was still a protostar 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

Then... Condensation of water vapor produced the earth's oceans With some water from comets Oceans swept out the carbon dioxide and locked it up into rocks (CaCO 3 )

What remained in our atmosphere was mostly nitrogen (N 2 )

Nitrogen Cycle Nitrogen moves from air to the soil to the plants and animals and back to the air

To get our present atmosphere we needed oxygen. How do we get it? –Plants: Stromatolites and algae at first Stromatolites Photosynthesis 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% –Argon 0.9% –Other: Neon, helium hydrogen methane H 2 O vapor 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 Weather occurs in this layer Warmest near ground, cools as you go up

Stratosphere 16km-50km UV absorbed by ozone in the stratosphere and it warms -50  at bottom to 0  C at top Many jet aircraft fly in the stratosphere because it is very stable Why does it warm with height?

MesosphereMesosphere 50-80km gases absorb little E 0  C at bottom to -90  C at top 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 Atmospheric O 2 and N 2 are stripped of electrons by solar radiation –reflects radio signals –Aurora borealis- northern lights

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

In between each layers are pauses A place where the temp is steady

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.

Pressure decreasesPressure decreases

The bottom of the troposphere reradiates absorbed solar E

The Atmosphere WS 13.1 Read directions carefully! Due at end of class! Think critically side Look at the x and y axis labels Find the temperature and pressure lines Interpret the graph and fill in the answers.

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.

Assignment Look at the transparency and answer the questions Homework: Answer the questions over the atmosphere from your book –A handout of the questions will be provided once

Remember the composition of the atmosphere? 78% nitrogen and 21% oxygen Those elements have weight