Big Bang and Earth's Early History Flashcards
The Earth formed approximately ___ billion years ago by ___.
4.56, accretion of debris from a solar disk
Tell me about the Hadean Era.
- Much of Earth was extremely hot; molten conditions due to bombardment and volcanism.
- Early atmosphere and oceans were formed by volcanism
- No oxygen
- Moon formed 4.51 billion years ago, which stabilized Earth’s obliquity and climate.
- Early atmosphere was probably mostly CO2 and N2.
Tell me about the Archaean Era.
- Bombardment ceases and Earth’s surface cools
- Faint Sun Paradox
- Atmosphere composed of volcanic and greenhouse gases
- First life forms, prokaryotes, which marked the beginning of this era.
- Earliest forms of photosynthetic life, namely cyanobacteria, also formed during this era.
- Oxygen is produced but concentrations remain low as it reacts with iron and is removed by rust (causing banded iron formation).
What caused banded iron formation?
Oxygen during the Archean Era reacted with iron and was removed by rust.
What produces oxygen?
Cyanobacteria
What’s the difference between the inorganic carbon cycle and the carbon-silicate cycle?
PRANK’D! Nothing at all – they’re the same thing.
Describe the carbon-silicate cycle.
Calcium carbonate is precipitated, subducted, metamorphized and returned to the atmosphere as CO2 by volcanoes.
How long does it take for the carbon-silicate process to complete one cycle?
0.5 million years
Life on Earth evolved as…
The brightness of the sun increased.
Weathering rates increase, because…
- Of the direct effect of temperature on chemical reaction rates
- Evaporation and, in turn, precipitation rates increase as temperature increases.
Silicate weathering is the loss process for…?
Atmospheric CO2
Atmospheric CO2 is lost during the process of…
Silicate weathering
What is CO2’s relationship with temperature?
Negative; CO2 concentrations tend to fall as temperature rises and increase and temperature falls.
Tell me about the Archean Era.
- Rise of O2 and global glaciation
- Early production of oxygen by cyanobacteria was rapidly removed from the atmosphere as O2 reacted with iron on the Earth’s crust, causing the formation of iron oxides.
- Rapid rise in O2 reacted with methane which reduced the greenhouse effect of the atmosphere, allowing the earth to cool with positive albedo feedbacks.
- Dissolved iron built up in the sea
- Ice prevented the exchange of oxygen with oceans
Tell me about the Proterozoic Era.
- Cyanobacteria continue to produce oxygen → atmosphere becomes oxygen rich → Great Oxidation Event occurs
- Snowball Earth began and ended this era.
- Eukaryotes form, including photosynthetic algae
- Sun at 90% of its current strength
