GEOG 2050 Chapter : Geography Chapter 3
Document Summary
Degassing atmosphere: 3. 8 billion years ago, earth cools, soild crust forms, dissolved gases from molten rock are released to atmosphere. Early atoms: 60% to 70% h2o, 10% to 15% co2, 8% to 10% n2, no free oxygen, (very different atmosphere on earth) Heavy precipitation period: 3. 6 billion years ago, earth continues to cool, water vapor condenses, clouds form, rain for thousands of years (creates oceans, most co2 removed from atmosphere to form limestone (caco2) Naturally occurring: chemical processes (o3, h2, geologic (n2, ar, ne, he, kr, xe, noble gases (ar, ne, he, kr, xe) Biological: photosynthesis, respiration, and decomposition (o2, co2, ch4) Man-made: (n2o, co2, ch4, o3) and other pollutants. Top of atmosphere (480 km, 300 mi: exosphere outer sphere, nearly a vacuum with scarce h2 and he extends to. 32,000 km (20,000 mi) from earth"s surface: gases layered by weight/gravity not evenly mixed. Heterosphere (layered: outer atmosphere, 80 km (50 mi) outward, to thermopause, <0. 001% of atmosphere mass.
