Don. Edwards wrote:These views are interesting but the reason the sea floor looks the way it does is because it is covered with water. If the ocean floors were free of water they really would look quite different. For one thing the big island of Hawaii would not be nearly as tall as it is with water. As a matter of fact most of the sea mounts we see in this view would be flatter. The oceans are what is holding those sea mounts steep sides up. If the oceans went dry the big island of Hawaii would crush down because of its own weight.
What determines slope is gravity - lower gravity means you can get steeper slopes. Unless you mean that the buoyancy of the water simulates the effect of lower gravity? (still, I'll ask someone at work tomorrow, it's got me wondering now you mention it - being a planetary scientist working in an oceanographic institute has its advantages
)
Also the unique look of the mid-oceanic ridges would probably change as well. They also would flatten out. Without the water and its intense pressures everything on the ocean floors would be much flatter and smoother. Also depending on just how dry the earth was the continents would probably be smoother and more eroded as well. The continental shelves would probably be gently climbing slopes much more like we see on Mars and Venus. Earths oceans are what make it look the way it does.
This I'm definitely not very convinced by... The ocean floors are
already flat and smooth - the slope on the abyssal plains is very shallow. And you get big mountain ranges where you have mid-ocean ridges because of the tectonic processes involved - whether there's water there or not doesn't influence their shape. True, eventually they'd reach a certain height and collapse under their own weight, but I don't think they're anywhere near tall enough to do that if they were exposed to atmosphere anyway.
I doubt if the continental shelves would look much different either, to be honest. There'd still be a drop-off at the ocean plate/continental plate boundary. Though I suspect the 'shelf' part would be largely indistinguishable from the part that would have been above water though, since there'd be no shoreline to speak of.
I really feel the Earth would look much more like Venus if we had no water on is surface. Also we would be seeing a great many craters.
You may be right on the first count, at least. Not sure about the craters though - Venus doesn't have a lot of them (only about 1000, IIRC?), most of the bolides burn up in the atmosphere, and besides which the crustal recycling has destroyed everything older than about 600 million years. Besides which, the oceanic crust recycling would destroy craters there very quickly (and that does take up about 70% of the earth's surface) - the only places they'd survive would be on continental shields.
Orpheus the rouge planet that is believed to have catastrophically collided and merged with Earth Mark I and the result was the moon
Is 'Orpheus' now the official name for the mars-like body that collided with Earth back then? I've heard it used a couple of times before now...
texture I had to take into account what the Earth would look like before it was covered by vast oceans. The best model for that is Venus. Venus has the makings of continents as well as many of the features we see on the Earth. I believe they have found seduction zones, areas of rifting which is a parallel to out mid-oceanic ridges. Not to mention volcanoes, mountains and canyons. If we really want to know what the Earth would look like without water all these things need to be taken into account.
Hang on a mo. There's a big difference between a 4.6 billion year old hothouse world and a world that's only a few hundred million years old! Venus' tectonism is rather different to Earth's - it doesn't have plates like Earth does, for a start. There's one area (Artemis Chasma) that
might be a
subduction zone ('seduction zone'?! Jeez, I know it's Venus we're talking about, but still...
), but it's practically unique on Venus. Yes, there's more volcanoes on Venus than you could shake a redwood forest at, and there are plateaus and mountains and rifts and canyons and craters too. But the tectonic style is different - it seems to consist of fixed plates that don't get created or subducted, but rather 'jostle' and shear past eachother, and the volcanism is centred around many hotspots and coronae on the surface. So you get long thrust and shear belts and rifts, but no 'conveyor belt' crustal recycling with one plate going under another. When last I looked, it seems that Venus regularly undergoes regional resurfacing in the form of massive lava outpourings when the crust thins every few hundred million years.
You migh still be right though - I gather than liquid water is considered one of the essentials for Earth-style plate tectonism. If the Earth didn't have water on the surface, it may be that plate tectonics would have never started, and our crust and surface would indeed be like Venus'.
As for theories about the early earth, what I got taught in my geology degree in the early 90s was that the increased heat flow of the early earth - and the presence of water - broke the crust up into lots of 'mini-plates'. Island arcs built up rapidly, that coalesced into continents, that themselves moved around on larger plates as the earth cooled. There'd be a lot of volcanism (erupting very hot, fluid lava), and not a lot of landmass to play with.
Dunno if those ideas have evolved much in the intervening decade, but there you go
.
If we are trying to envision Earth without an atmosphere than look no further than the moon for the colors you will need. The moon being made of essentially the same thing the Earth is made of, the Earth would have the same coloring without an atmosphere, very gray. I don't think much in the way of color would be seen.
Well, the oceanic crust would be darker than the continental crust, if such divisions and tectonism still existed (I can't for the life of me think of any reason for Earth
not to have an atmosphere, with all that volcanism going on though. But what the heck, it's a thought exercise
). I guess the earth would have 'maria' like the Moon, but they wouldn't be circular patches, they'd be the shape of the 'oceanic' areas.
If we are trying to Earth with an atmosphere much like Mars’ than there would be a great deal of wind erosion and again the whole planet would look different.
I may be a bit out of touch on this, but isn't Mars supposed to have very
weak aeolian erosion processes? There's not a lot of 'oomph' in that thin atmosphere. I'd imagine that there'd be a lot
less erosion on an Earth with a thin atmosphere than there is today, especially given that a lot of crust would be new as it was created at the mid-oceanplate-ridges.
The surface would probably be covered with vast dune fields again like we see on Mars. So much of the lower areas would be covered in sand and sand-dunes.
Again, I'm not sure about this. I suspect the old continental shields might be more eroded, sure - but the ocean crust would be a lot 'sharper' since it'd be newer. I'd imagine the whole planet would be covered by a regolith of varying thickness though, so I guess that could form into dune fields...
. I hope things work out... it sounds like an interesting project.