Someone please assuage my doubts about Pangea.?

Question

I am a solidly scientific-minded person, but I have long been uncomfortable with the Pangea theory. Sure, we have continental drift and it gives a good indication of how the continents are spreading, but what would have caused all the land mass to form on one side of the earth and then break up like it never should have been that way in the first place? What caused the bulge? And why would all of this spreading have occurred so recently, geologically. It seems to me that this would be a good creationist objection to evolution: so many species having such recent common ancestors on this big, single continent? Then it broke up and was separated by oceans? I haven't heard fundies use this objection yet, but I'd like to know, myself.

First two answerers, thank you, but keep in mind that the events you are both talking about were over 3 billion years ago. At one time I thought maybe that big collision which caused the moon might have been the cause of continental asymmetry. But I still can't understand the timing. Why would it remain stable for 3 billion years and then suddenly break up, (after all that cooling and thickening of the crust), and distribute the pieces all over the globe in only a few tens of millions of years. That's only about the last 1 to 5 percent of the time since Pangea formed.

Answer 1

As other answers have mentioned, Pangaea was only the last in a series of super-continents. The hypothesis I favor is that a large landmass affects the dynamics of mantle convection, effectively concentrating a plume under the landmass. The resulting rifts then break the super-continent into smaller components much as the rift in Africa is doing today. With the Earth being a finite oblate spheroid, eventually these smaller landmasses will coalesce in a different location to form another super-continent.

Answer 2

Continental drift is caused by the convection currents in the mantle. Each convection cell is, necessarily, very roughly spherical because the mantle is too viscous to permit any other convection pattern. At present, the thickness of the mantle relative to the core means that there are about a dozen major convection cells, and the plates of the lithosphere are migrating towards the junctions of descending currents.

In the Earth's earliest history, the core had not yet separated out, and its iron and nickel were distributed throughout its body. As the dense metallic substances settled towards the centre by gravity, the core began to grow and generate the heat which drives the convection currents. The simplest convection pattern in a sphere with a point heat source at its centre is a single rotating cell with a descending current at one point and a rising current at the diametrically opposite point. All of the first lithospheric plates drifted on the surface current to gather over the single descending point and, voila, Pangaea.

As the core grew, the single-cell convection pattern would become unstable, and when it flipped over to a multi-cell pattern, Pangaea broke up. Each further stage of growth of the core would replace the previously-stable pattern of convection cells with a newly-stable pattern which had more but smaller cells, and no matter where the lithospheric plates had been before, some of them would have to break up and others would have to start moving.

Answer 3

In the beginning, the earth was in molten form, inside out, every where, 5.5 billion years ago.

As soon as it came into being, it started cooling down by giving the heat to the space around it. That molten stuff got some shape to become solid after about 1 to 1.5 billions years.
This solid state was confined to just a "small" area, called Pengae. This was a small piece of "land" which grew wider later on, slowly but steadily. This process resebmles to the cream on hot milk.

As the earth continued to rotate around the its own axis in addition to its revolution around sun, and more over due to capturing Moon in its gravitational field, this peice of land started breaking up into an irregular manner.

It is now well known fact that at different parts of the globe, the thickness of this top layer (the cream) called crust is different, varying between 70 km(thickest) to 14 km (thinnest).
Beneath this is the original form, the molten state (the hot milk) of constituents material. This inner portion is called Mantle, over which the crust "floats" while rotating and revolving and being affected by the gravitational pull of the moon and sun and stars and beyond.

At some places the crust is eventually cracked, out of which comes the low-lying mantle out; in the form of lava. This is happening on the continents as well as under the oceans. These places (volcanoes) are "like" weaker or soft locations of the crust.

The body of the cracked parts of the crust are given the name of a "plate", like the Indian plate, the Russian plate etc. At the edges of these plates, is happening, what we call continental drift, which is over-riding of one plate and subversion of the other under the over-rider.

This is a never-ending story.

The drifting, the movement and the slipping is a continuous process. The huge parts of the crust are moving away from each other and becoming closer on the other side.

This beauty of the irregularity of the events is the cause which compelled you to ask this question.

Answer 4

Well, rest easy. You don't need to fear that you're being fed some kind of deus ex machina scenario.

The fact is, Pangaea is only the most recent of the past supercontinents. The supercontinent cycle periodically brings all or most of the planets landmasses into huge ones. These big landmasses will have different configurations every time, and will be positioned at different latitudes as well.

This is just as would be expected, given the mechanics of plate tectonics. It's going on now, it has gone on as long as there have been crustal plates moving across the mantle, and it will continue on into the future. Probably all the way up until the sun dies.

Incidentally, both the Americas and Eurasia (or Africa-Eurasia) are considered to be modern supercontinents. Just not all-inclusive ones.

Some past (near all-inclusive) pre-Pangaean supercontinents:
Pannotia
Rodinia
Columbia (or Nuna)

And possible future ones:
Pangaea Ultima
Amasia

Answer 5

There are also theories that say the Earth was molten more then once.
It was when it first formed, cooled and then it collided with a planet and that created the moon and the earth was molten again.
There were other land masses before Pangaea. I asked that question last week. Take a look at what they said.
http://answers.yahoo.com/question/index;_ylt=Ao9TMMTK1qQann0Y48MpkQnsy6IX;_ylv=3?qid=20070917172036AAgWxPU