3-4-07 Pangea

There's an intriguing geological sequence of continental drift, generally agreed to be an accurate description of how the Earth has looked over the course of the past 250 million years. This sequence begins with the supercontinent called "Pangea." It's composed of all the present day land mass on Earth, all smashed together.

Here's a drawing of how that is supposed to have looked. As you can see, there is basically one big continent and one big ocean.

Next, we have a drawing of what it looked like 180 million years ago. Pangea has split into a northern continent named Laurasia, and a southern continent named Gondwanaland.

The next drawing shows the breakup of Gondwanaland, as it was occuring 135 million years ago. And here we have how all the continents are believed to have been positioned around that point in time.

Finally, we get the familiar mercator projection world map as it looks today.

The develpment of the data behind all this has gone on for many years. The geological phenomenon of "continental drift" was eventually brought to these conclusions regarding what's been going on with it over the course of the past 250 million years, and now we have the Pangea story.

A recent article about how the Earth's crust is missing in a large area of the mid-Atlantic, and the Earth's mantle is exposed in this area, is what prompted me to come up with today's blog entry. It's an area at the midpoint of where Europe and North America drift further and further apart. The "mid-atlantic" has a lot of volcanic activity, as these plates keep spreading apart under the ocean. The only land mass on this split is Iceland, which is rife with volcanic activity. And it is, oddly enough, on the exact opposite side of the planet from the Pacific Ocean.

It's the Pacific Ocean that needs more explaining, in my view...

At any rate, all of the above seems to lend more and more weight to the theory that the Moon may have originally been part of the Earth, or that maybe the Earth was hit by an asteroid way back in geological time, and this impact ended up creating the Moon. These various theories, and I don't know which one is more generally accepted at this time, generally line up on one point, however, and that point is that the impact happened on the side of the Earth that's now the Pacific Ocean.

So, way before Pangea, back in the range of 2 billion years ago, it can be plausibly theorized that some sort of huge impact occured to explain why there would be only one land mass on the exact opposite side of the planet 1.75 billion years later (250 million years ago), and why all the land mass of the planet ended up spreading out from that side, and there yet remains the largest ocean in the world on the side that was impacted.

The article about the exposed mantle under the middle of the Atlantic Ocean lends some credence to the idea that the Earth's crust is still "adjusting" to the damage done by some theorized impact around 2 billion years ago.

It's all very interesting to see how this information has been developing over the years, as more and more research has been done to bring these ideas into focus.