| Question |
 |
|
| Answer |
|
|
| The Hadean Time? |
First 600 Ma, B4 first rocks, time of huge impacts |
| Oldest rocks |
4.0 Ba |
| Oldest mineral? |
Zircon (western australia) 4.2 Ba |
| Zircon? |
A mineral in granite, i.e. the main rock in continents |
| The oldest rocks? |
Ultra hot pillow lavas (1600 degrees c) Proves the was already an ocean and earth was hotter below the surface |
| Source of gas and water? |
60 - 70% of the gas from volcanos is water vapour, rest is CO2 and N2 |
| How did oceans form? |
Condensation of water vapour |
| Composition of early atmosphere? |
60% carbon dioxide, 30% Nitrogen, 10% argon |
| Composition of current atmosphere? |
78% Nitrogen, 21% Oxygen, 1% others |
| Evidence for oxygen poor atmosphere? |
Pyrite and uraninite pebbles in ancient conglomerates. Palaoisols are all grey (acient soils), and early oceans had dissolve oxgyen in them which is impossilbe with oxygen in the atm. |
| Where is oxygen produced? |
Small amounts in upper atm as UV light splits water vapour up. (photodissociation. Also Photosynthesis. |
| Evidence for dissolved iron in oceans? |
Banded Iron formations, formed in shallow marine environments bewteen 3.5 - 2.0 Ba |
| Progression of Oxygen? |
3.8 Ba microbes producing O2 in the ocean and precipitiaing BIF's. BIF's stopped at 2.0 Ba and red beds were formed on land, indication oxygen in atm. |
| Plants invaded continents? |
0.4 Ba. |
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