questions 2 Flashcards
what 2 elements were made when the universe cooled after the Big Bang?
H and He
how are heavier elements than Fe made?
neutron capture and supernova
what is accretion?
rocky planet formation
what heated up the earth during formation?
radioactive decay
what forms most of the mantle?
Si
how old is earth?
4.5 Ga
how was the moon formed?
collision with the planetary embryo
where do oceans and the atmosphere come from?
outgassing of volatiles
2 abundant gases in the early atm
CO2 and N2
how old is the first proposed evidence for life on earth?
3.8 Ga
how old are the oldest fossils fo life?
3.5-3.3 Ga
what evidence supports sea floor spreading?
symmetric magnetic reversal either side of the mid Atlantic ridge
what is rifting?
the process of continents splitting apart
name of the ancient bits of continental crust
cratons
what co-existing gases represent disequilibrium in the atm?
O2 and CH4
what gas dominates the atmospheres of Mars and Venus?
CO2
what does the Gaia hyp propose is being regulated by life?
atm
what is the habitable zone?
the distances from a star compatible with liquid water
how much less luminous was the sun when earth first formed?
30%
what kept the early earth warm and so allowed liquid water on the surface?
higher amounts of CO2, lower albedo and higher amounts of CH4
what process removes CO2 from the atm?
silicate weathering
what counteracts the steady brightening of the sun?
accelerated silicate weathering
when were the first stromatolites?
3.5 Ga
