Week 5
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What makes earth habitable?
Goldilock’s distance Carbon abundance Insulating atmosphere Liquid water Magnetic field
When was the formation of earth?
4.57bn years ago
What is the period of 4.57bn years ago called?
The Hadean
What are the events of the hadean period?
Cooling and differentiation of the earths layers Stabilisation of the atmosphere Great impact
How old are the oldest rock records?
Only 4.03bn years
What caused the differentiation of the earth’s core?
Bombardment of asteroids delivered more material Metal will separate from the silica Metal will sink towards the centre of the planet forming a core
How did earth maintain light elements?
Comets, and early proto planets with carbon- rich cores delivered very light volatile elements
How did the moon form?
The collision of Theia, 4.53bn years ago added material to the earths core and sent debris into orbit The orbit coalesced and formed the moon
What was the Hadean atmosphere like?
Toxic dense and smoggy, volcanic activity released volatile gases into the atmosphere CO2 and methane created insolation
When and how were our oceans formed?
4.4bn years ago the earth cooled enough to support liquid water. Water vapour that had accumulated in the atmosphere condensed and rained down creating acidic pools of water.
When was the Archean period?
4.0-2.5bn years ago
What were the events of the Archean period?
Late heavy bombardment Plate tectonic formation Earth’s magnetic field Atmospheric development
How did the magnetic field form?
Convection currents churns the liquid outer core and generates electric currents which powers the earth’s magnetic field
What was the late heavy bombardment?
The continual attack of asteroids causing damage to the young crust and vaporizing the ocean
What is the evidence for a permanent ocean?
The formation of metamorphosed sedimentary rocks
What was the atmosphere like in the archean period?
Most H2O would’ve been lost when the ocean formed. The ocean also becomes a sink for CO2 removing it from the atmosphere Remaining atmosphere would be high in nitrogen
What defines a prokaryote?
No membrane bound organelles DNA is free floating 70S ribosomes Asexual reproduction Unicellularity, binary fission
When was the oldest eukaryote fossil formed?
Grypania 2.1bn years ago
Development of life timeline
Simple polymers Prokaryotic cells=3bn years Photosynthetic cells Cyanobacteria Smaller cells within larger cells First eukaryotic cells =2bn years
What are stromatolites?
Microbial mats built from bound falling sediments
What is the oldest stromatolite?
3.4bn years
What was the first evidence of sexual reproduction?
Bangiomorphia pubescens- red algae 1.05bn years ago
How can we look for signs of life?
Body fossils- the physical remains of an organism Trace fossils- Evidence of activity such as footprints Chemical footprints- Such as pigments, dna or sterols
How many ice ages were there?
• Sturtian glaciation • Marinoan glaciation • Gaskiers glaciation