System Earth Ch 10 Flashcards
What are the four eons in order?
Hadean
Archean
Proterozoic
Phanerozoic
What does the precambrian refer to and why?
hadean, archean, proterozoic are all precambrian
shelly fossils become abundant at this point in the fossil records
formation of solar nebula
from interstellar clouds that collapse to form a star. The cloud has to be very cold as it then has less internal pressure to counteract gravity and can therefore collapse on itself.
formation of planets
nebula from the sun is heated and solid material condenses from gases, creating rocky planets.
Cooler nebula condenses into gas form
accretion
the accumulation of floating stuff to form planets
why is Jupiter so important?
its core accreted early enough to caputre large amounts of hydrogen and helium from the solar nebula before it dissipated
It prevents comets from reaching the Earth because its gravitational pull is so strong
giant impact hypothesis
a huge planetsimal collided with earth and split up into little pieces,
impact degassing
continuous bombardement of the surface, releasing large amounts of water and other volatile compounds into the air.
how do we know the earth was bombarded?
moon, mercury and mars were too.Dating the moon craters, it’s clear that it was a recurring thing. If the moon was getting hit, it is only logical the Earth was too.
Nice model
predicts that all the bombardment occured at one.
Earth’s early atmosphere
O2 practically zero, no photosynthesis
N2 was probably quite high
CO2 - we don’t know, there are no rocks and it could have been anything.
strongly reduced atmosphere
rich in h-containing gases, eg methane and ammonia
Miller - Urey
experiment regarding protein formation in early planetary development
RNA
some believe this evolved before amino acids and we just didn’t have DNA for a long time. RNA molecules would be able to duplicate themselves without the need for help from another molecule.
origin of life?
serpentine minerals
formaldehyde
hydrogen cyanide
