Pangaea

[ihwip]

I just had a thought. Is it possible that the continents were caused by the impact that created the moon? A mars-sized body would have erased any symmetry and produced a bulge. As water formed this bulge was left above the water and it is slowly dissipating and spreading out. This cycle would naturally pushed toward a uniform altitude and eventually all land mass would be covered by ocean.

I don't think it is too implausible. Any thoughts?

 

[MeteorWayne]

There would not have been a bulge, the entire planet melted so it formed a sphere. Also, Pangea is a recent continent, from only 250 Million years ago. Many other supercontinents existed well before it.

Now there is a theory that the first small continents may have been sparked by later impacts...much later than the moon creation one which occurred within the first few million years of the earth's formation.

 

[Gravity_Ray]

I have always been fascinated by the continents. It’s always amazing to me to know that the surface of this planet is in effect "boiling". To know that something that seems so solid is actually very liquid really drives it home to me that the universe is always changing, but we are just not able to comprehend it. Which feeds to my idea of God and why we cannot perceive him.

Anyway, as MW states Pangaea is pretty young actually. The oldest continent that there is evidence for is called Rodinia and its probably around 750 million years to 1 Billion years old. Actually there is evidence that there was more land masses before that. The oldest is from Jack Hills in Australia which date to about 4.3 to 4.4 Billion years ago.

The Moon is about 4.5 Billion years ago, so pretty quickly after one of the biggest (if not The biggest) Kabooms of this planet, Earth face was changing and creating continents. Here is the list of names based on age of rock formations:

Earth Theia impact 4.5 Billion years ago

Yigran Craton 4.3 – 4.4 Billion years old
Vaalbara 3.6 Billion years old
Komatii Formation 3.5 Billion years old
Ur 3 Billion years old
Kenorland 2.7 Billion years old
Nena 1.8 Billion years old
Columbia “Nuna” 1.5 to 1.8 Billion years old
Rodinia 750 Million to 1.1 Billion years old (probably the oldest “continent” that there is semi proof for)
Pannotia 540 to 600 Million years old
Euramerica 300 Million years old
Pangaea 180 to 300 Million years old
Laurasia 60 to 300 Million years old
Gondwana 30 to 600 Million years old

And here is a good site that I really like for this kind of stuff:

http://www.ig.utexas.edu/research/proje ... recons.htm

 

[ihwip]

Wow. Thanks for all the info!

I was thinking that the molten earth would more viscous after the moon was created. Perhaps the collision created some kind of internal dynamo that is still generating the continental drift. It would have contributed to the earth's rotation and modified its orbit depending on the velocity right?

 

[Gravity_Ray]

Im sure the collision changed the Earth forever. Cerainly it contributed to the spin, although nobody knows for sure because almost all the evidence is wiped out.

The collions theory is still being worked on. Its not for sure. There are some holes in the theory, but its a good working theory so far.

 

[MeteorWayne]

Wow. Thanks for all the info!

I was thinking that the molten earth would more viscous after the moon was created. Perhaps the collision created some kind of internal dynamo that is still generating the continental drift. It would have contributed to the earth's rotation and modified its orbit depending on the velocity right?

With the extreme temperatures after the impact, the magma would have been less viscous. That's when the iron that makes up the earth's core fell through the rest to the center, as it has on all of the fully melted bodies in the solar system.

 

[3488]

I have heard something similar Wayne, also the differing imapct velocities on the Jupiter moons Ganymede & Callisto has been argued as their fundemental different geological histories, with Ganymede being closer to Jupiter, suffering higher velocity impacts than Callisto, thus the extra engery in those causing Ganymede to differentiate, whereas Callisto did not.

I think the truth is more complicated than that, Ganymede's greater overall mass than Callisto's being a part, but certainly differing energies from impacts being a part. Ganymede too appears to have had a geological 'revival' approx 1 GYA, which as yet has not been explained (Ganymede's orbit around Jove may had changed temporarily causing additional internal heating, a vastly reduced version of what is currently happening on Io).

The Earth almost certainly underwent a major differentiation event hense the dual layered core, being very distinct from the mantle. Perhaps a gigantic impact did create the Moon, I am still not 100% convinced by that, but certainly the energey from that would have melted the Earth entirely (worth mentioning the crust of Earth would have barely formed at this point), causing a secondary differentiation episode, but then Earth's greater mass & density overall would create enough pressure internally to keep temperatures high enough to allow for further differentiation.

Worth mentioning the planet Mercury just like Earth appears to have a double layered core, but Mercury with a mass of only 5.5% that of Earth woulld lack the internal pressure & thus temperatures for further differentiation. Perhaps in Mercury's case the location of where she formed & the higher abundance of Metals vs Silicates plays a part. Yet Venus appears to only have a single layered core, go figure.

This subject is far more complicated than it first appears.

Andrew Brown.