Earth History

Page
5

Temperature

K

Venus

Earth

Mars

ICE

WATER

VAPOUR

Triple Point

1

10-6

200

380

Slide 35

Water ( Solid,Liquid, Gas)

The Surface temperature of the Earth at 1 atmosphere Pressure is close to the Triple Point for water.Water is the only compound that can exits in the environment as a Solid, Liquid and Gas simultaneously.

The thermodynamic properties of Water have been essential in determining our present climate and support of life.

Slide 36

Super Greenhouse & Acid Rain

On Venus ,the high level of CO2 and its distance from the Sun have lead to a super greenhouse effect and Sulphuric Acid Rain. Where the surface pressure in 90 times that of Earth’s ( 900 m in the Ocean)

and surface temperature is about 460oC

(Melting point of Zn = 419oC)

Slide 37

Current Atmosphere

Composition of Current Atmosphere %Vol

N2, O2, Ar, CO2, H2O

78.08 20.95 0.93 0.03 (Variable)

ppm Ne He K CH4

18 5.2 1.1 1.25

Early Atmosphere Rich in CO2, CH4

Slide 38

Present Level of Oxygen

The present level of Oxygen in the atmosphere is balanced at a such a level that less would impede survival of a number of organisms while more would lead to a greater probability of fires.

At 25 % oxygen damp twigs and grass of a rain forest would ignite.

Slide 39

Structure of Atmosphere

Earth’s Atmosphere

Earth’s Surface

Troposphere

Stratosphere

Mesosphere

Thermosphere

REGION

10-16 km (-56oC)

50 km (-2oC)

85 km (-92oC)

500 km (1200oC)

15oC

O3

O2+, NO+

O2+, O+, NO+

N2,O2,CO2,H2O

3 x 10-6 atm

0.001 atm

0.1 atm

1atm

Slide 40

Ozone Layer

Ozone in the Stratosphere

 16 - 50km above the Earth’s Surface

acts as a blanket preventing harmful radiation that can marked affect living material from reaching the surface of the Earth.

Slide 41

Ozone and Radiation

Oxygen that lies above the stratosphere filters out UV light 120nm - 220nm

Ozone O3. In the Stratosphere filters

out UV light 220nm - 320nm

Regions UV C 200nm - 280nm

UV B 280nm - 320nm

UV A 320nm - 400nm ( less harm)

Slide 42

Effects of Reduction in Ozone