Chapter 3 Outline

Chapter 3 Outline - Chapter 3: Earth's Modern Atmosphere...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 3: Earth’s Modern Atmosphere  Atmospheric Composition, Temperature, and Function Modern atmosphere ~4 th general atmos in Earth’s history; mainly air + major industrial, chem. raw material; air- simple mix of gases, naturally odor-/color-/taste-/form-less, blended as if single gas; modern atmos earth’s protective membrane; its top ~480 km above Earth’s surface; beyond that: Atmus rarefied (~vacuum), called exosphere ; contains scarce lightweight H & He atoms, weakly bound by gravity as far as 32K km fr Earth Atmospheric Profile Modern atmos in series of imperfectly shaped concentric shells/spheres that grade into each other, all bound to planet by gravity; atmos thin- < 1/1,000,000 th Earth’s total mass; 3 atmos criteria: function, composition, temperature (see pg. 62); atmos exerts weight due to gravity: air molcs create pressure: Exerted on all surfaces in contact w/air; weight (force over unit area) of atmos- air pressure ; gives force ~1 kg/cm 2 at sea level; gravity compresses air- denser near earth surface, thinner w/incr alt; less air pressure= less oxygen/breath; 50%+ of tot mass of atmos compressed below 5500 m… 75% under 10,700 m, 90% under 16K m; sea lvl- air pressure 1013.2 mb (millibar- measure of force per m 2 of surface area)/29.92 in mercury (Hg)/101.32 kPa (kilopascal; 1 kPa = 10 mb) Atmospheric Composition Criterion Under chem. composition criterion, atmos divides into 2 regs: heterosphere (80-480 km alt) & homosphere (earth’s surface-80 km alt) Heterosphere Heterosphere - outer atmos in terms of composition; extends to transition to exosphere/interplanetary space; nonuniform- gases not evenly mixed; gases occur in distinct lyrs sorted by gravity according to Homosphere Homosphere - atmos rapidly changes density here, toward Earth surface, but blend of gases ~uniform except concentration of ozone (O 3 ) in ozone layer (19-50 km), varied water vapor, pollutants, trace chems; present stable mix of gases evolved slowly- 500 mil yrs ago; contains much ~inert nitrogen : Key element of life, esp from the N-containing foods we eat; oxygen also essential- diff %s in atmos due to varied photosynthetic rates w/lat, seasonal changes, lag time as atmos circulation mixes air; forms 1/5 of atmos + compounds tht compose ½ Earth’s crust; readily reacts w/many elements Argon - %1 of homosphere- inert (unreactive noble gas), unusable in life processes, but industrial/ commercial uses; carbon dioxide natural by-product of life processes; stable; impt at maintaining global temps; atmos % has incr’d fr 0.038% due to human activities Atmospheric Temperature Criterion Thermosphere Similar to heterosph alt at 80-480 km; upper limit of thermosph= thermopause ; during pers of less active Sun, it may lower in alt to 250 km; active Sun causes it to incr to 550 km; temps rise sharply in
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

Chapter 3 Outline - Chapter 3: Earth's Modern Atmosphere...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online