Theory on How land came about on water dominated Earth

[dgoodpasture2005]

If Earth is 70% water, and we see land being created by volcanoes... then would it be safe to make an ASSUMPTION that Earth may have once resembled something such as the moon EDIT: Europa. Covered fully in liquid water until comet impacts and volcanoes eventually gave way to land mass? Now i must be able to explain Pangea... how did all the land pop up in the same place at once? perhaps the Earth at that time, was only spewing lava in one location.. it's plate tectonics were just getting underway.. is it not safe to say? Pangea slowly ripped apart forming new faults, ring of fire etc. I have not thought this through to much, nor have i done any studies, it;s just an idea at the moment, but 'id like some input if you could thanks, positive or negative, but please explain your position, so i can gain some data and more ideas as well... Thanks

David.

 

[Bystander]

10¹⁸ tons of water in 6x10²¹ tons planetary mass ain't 70% --- do not confuse surface area ratios with mass.

 

[dgoodpasture2005]

ah yes, sorry, i meant surface area water... i can picture an Earth covered in water only... but i don't have exact depths etc... or i could calculate how much water would cover land if land was distributed evenly throughout the Earth. This could also help back up evolutionist who argue we evolved in the Ocean. I don't want to get to far ahead of myself yet.

 

[Andre]

Well on the back of an envellope with gross gestimations. If the average dept of the oceans (70%) is -3000 meter and the average land elevation (30%) is 500 meters, then a perfect geoid shape without elevation differences would have been covered with 2100 + 150 = 2250 meters of ocean. Roughly of course.

 

[dgoodpasture2005]

this is great, thanks Andre and Bystander. I think we can all work on this here at physics forums, there are some great minds here... this seems like a plausible theory to me.

 

[matthyaouw]

Pangea was not the original landmass. It formed from several smaller ones (sutre belts marking the joining points include the Atlas, Ural and Appalachian mountains). Two previous supercontinents are also thought to have existed prior to this- Pannotia and Rodinia, but these too formed of pre-existing land masses.
http://en.wikipedia.org/wiki/Pangea

It's thought that the first crust was basic (alkaline) much like modern oceanic crust, and was short lived, leaving little to no evidence of it's existence. A little acidic (continental) crust is likely to have formed at subduction zones as island arcs, much like today. Partial melting and rising of granite bodies either during subduction, rifting or heating could account for the early continental crust. It is thought that direct vertical accretion of continental crust from the mantle played a more significant role in early formation than lateral accretion such as along subduction zones.

It's very hard to tell what happened in the early history of the earth, as most early rocks (if they survived) have been severely altered by subsequent events. One of my textbooks (possibly webster) said something along the lines of:
"Interpreting precambrian events is like solving a crime where 99.9% of the evidence has been lost, destroyed or altered"

 

[Plastic Photon]

I think you started too late in the Earth's life with your theory. Last night on NGC there was a program which stated water most likely came from an asteroid (other celestial body) impact 50 million years into the existence of Earth and a few more hundred million years for it too spread into massive quantities by biological process. Actually a bit of a lie, they meant oxygen and water but close enough I suppose.

Has there ever been a time in which the Earth was completely swamped in water? And are you asking about plate tectonics or a landmass protruding from the water?

 

[matthyaouw]

Magma contains a significant amount of water too, and it often escapes during volcanic eruptions. I'm not sure how much of the ocean can be attributed to this, but I'd guess a significant proportion.

 

[Zygotic Embryo]

Tectonic Plates along with continental plates.colliding under the earth, causing a fault in the Earth's core..resulting in magma spewing out, dehydrating bits of water and creating land ( under water) and eventually the underground bits of land formed surface land...?

just an idea..