GEOG 1 Chapter Notes - Chapter 3: Atmosphere Of Earth, Stellar Atmosphere, Thermosphere
16 Jul 2018
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CHAPTER 3 Earth’s Modern Atmosphere
I) Atmospheric Composition, Temperature, and Function
A) Principal substance of atmosphere is air, a simple mixture of gases that is naturally odorless, colorless,
tasteless, and formless, blended so thoroughly that it behaves as if it were a single gas
B) Beyond the altitude of atmosphere is exosphere, where the rarefied, less dense atmosphere is nearly a
vacuum (“outer sphere”)
C) Atmospheric Profile
a) Scientists use 3 atmospheric criteria (composition, temp, function) to define layers for distinct analytic
purposes
b) Air molecules create air pressure through their motion, size, and number; changing throughout the
atmospheric profile
c) Atmosphere has weight because gravity; gravity compresses air, making it denser near Earth’s surface
D) Atmospheric Composition Criterion
a) Heterosphere
(1) The outer atmosphere in terms of composition
(2) Less than 0.001% of the atmosphere’s mass is in this rarefield heterosphere
(3) Region is not uniform; its gases are not evenly mixed and in distinct layers sorted by gravity
according to their atomic weight, with the lights at the margins of outer space
b) Homosphere
(1) Below heterosphere, extending from an altitude of 80 km to Earth’s surface
(2) Blend of gases is nearly uniform throughout; exceptions in ozone layer for concentration of ozone
(3) Air is a vast reservoir of relatively inert nitrogen which integrates into our bodies not from the air
but compounds in food
(4) Oxygen from photosynthesis is also essential; 1/5 of atmosphere but ½ of Earth’s crust
(5) Argon = <1% of homosphere; completely inert and unusable in life processes; commercial,
medical, and industrial use
c) Carbon Dioxide
(1) A natural byproduct of life processes, a variable gas that is increasing rapidly
(2) Small percentage in atmosphere, but important to global temps
(3) Increase is accelerating, expecting to bring irreversible ice-sheet and species lossess
E) Atmospheric Temperature Criterion
a) Thermosphere
(1) “heat sphere” roughly corresponds to the heterosphere
(2) The upper limit of the thermosphere = thermopause = “to change”
(3) Temperatures rise sharply; not hot but excites individual molecules = kinetic energy – the energy
of motion, is the vibrational energy that we measure as temperature
(4) Heat is when kinetic energy is transferred between molecules
(5) Thermosphere is not “hot” because the density of molecules is so low that there is little actual heat
b) Mesosphere
(1) Area from 50 to 80 km above earth and is within the homosphere
(2) The outer boundary (mesopause) is the coldest portion of the atmosphere
