ESS102H1 Lecture Notes - Radioactive Decay, Hadean, Water Cycle
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Published on 8 Feb 2013
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GLG205 Lecture 1: Jan 10th, 2013
EARTH SYSTEM:
Each system needs matter and energy
Earth system has 4 major parts:
- Atmosphere: a mixture of gases
- Lithosphere: upper part of the solid earth
- Hydrosphere: the total water on Earth
- Biosphere: living and dead organic matter
Two sources of energy for Earth system:
- External energy: radiation from the Sun, drives the water cycle and wind
cycle
- Internal energy: caused within the Earth by radioactive decay (e.g. plate
movements)
Types of Change:
- Gradual: slow over millions/ billions of years
- Catastrophic: fast from seconds to centuries
- Unidirectional: irreversible change (formation of earth)
- Cyclic
Rising human pop requires ENERGY and RESOURCE CONSUMPTION
Result: ozone hole, air/ water pollution, deforestation, etc
GEOLOGICAL TIME
Universe created by a big explosion: THE BIG BANG
Hot clouds of hydrogen and helium formed giving rise to the stars and the planets
Evolution of Earth:
HADEAN 4.5 – 3.8 billion years ago
- Radioactive decay caused melting of the early Earth
leading to internal differentiation: heavy elements (iron, nickel) settled in
the inner core, lighter elements settled on the outside forming the mantle
- Atmosphere had lots of gases especially CO2 (kept the earth warm in the
absence of ozone layer) and no oxygen
ARCHEAN 3.8 – 2.5 bya
- At 2.4 bya, First photosynthetic bacteria evolved
oxygen was entered into the atmosphere; ozone layer formed