CHAPTER 11
OTHER CONTINENTAL QUESTIONS

   
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There are some other aspects of continental uplifting and movement that should be covered. That is the purpose of this chapter.

INEVITABLE CONTINENT CLUMPING

The nature of subduction and the directional movement of new continents pretty much guarantees that, over time, continents will inevitably end up clumping together. They will subduct the oceanic plate in front of them until they run into another continent.

However, new cosmic impacts can cause the creation of new continents that will then inevitably clump together through subduction.

Eurasia is, in effect, the graveyard of older, clumped continents, drawn together over the eons.

RECONCILING THE NUMBER OF IMPACTS AND THE NUMBER OF CONTINENTS

The Earth is 4.6 billion years old. If a continent-producing impact were to hit every 50 million years (approximately the present rate), then why wouldn't we have 90 continents on the surface of the Earth today?

First of all, the rate of impacts was much higher in the early years of the Earth's history. The hot surface of the Earth was made and remade again and again and again by large scale impacts. One impact was so huge that it created the moon.39

After 3.8 billion years ago, the period of extreme impacts was over and things settled down. Somewhat. There were still lots of impacts. Gradually, the impacts began to taper off, to a level approaching modern day.

There are two things to consider about the early Earth's surface, which was thinner because the Earth was hotter.

1. SMALLER CONTINENTS — Because the Earth's surface was thinner, it meant that there was not so much shear friction to overcome when uplifting a continent. Therefore, smaller impacts could cause the uplift of a continent. Also, smaller continents were possible, creating the small, old "cratons" that are found embedded in some of today's continents.

2. LOWER UPLIFT — Because the energy needed to uplift an area of crust was lower, the amount of uplift distance needed to create pressure relief was lower. Continents were not uplifted as high. Some of the early continents may not have been uplifted as high as sea level.

The natural process of subduction, begun by the directional pressure on the lithosphere of a newly created continent, would eventually cause all of the continents to coalesce. And then a new large impact would create a big, new, directed continent, which would eventually clump due to subduction.

When we look for all these older continents that should be there, we will find that many of them have been absorbed by the bigger continents and squashed together through the process of subduction. I believe that there is a reason that so much of the central Asian land is so high … compressed continents from the early Earth are part of the story.

As the Earth cooled, the lithosphere became permanently solider and deeper. A thicker lithosphere made it more difficult for an impact to uplift a continent, and as a result, the uplifting became rarer and, when it happened, the uplifting was higher.

With the thicker present day lithosphere, the continent of Western Antarctica is about as small as can be created at the antipode of an impact.

What we have seen since the end of the great bombardment, ending about 3.8 billion years ago, is:

1. EARLY YEARS — Still significant impacts creating many sizes of shallow continents. These continents were eventually squashed together through the subduction process (caused by directed pressure on surface tectonic plates by newly created continents).

2. LATER YEARS — A lower level of impacts and only occasional continental uplift, averaging about one every fifty million years. But when it happened, it was a good-sized continent (compared to the size of the small cratons of the early days) and the uplift height was significantly higher.

During the past 250 million years, we have seen the creation of the Siberian Continent, the Western Antarctica Continent , the Eastern North American Continent, The South American Continent and the Indian Continent. Two of these (India and Siberia) ended up in the graveyard of old continents (Eurasia). Another ended up attached to Eastern Antarctica. The other two are free floating but headed towards Asia.

The other continents that would still need to be matched up with impacts are:


1. Africa

2. Australia

3. Different areas of Eurasia

Taking into consideration the natural process of continental coalescing and the number of continents that have not yet been identified with an impact, there seems to be enough unexplained continental material to match up with as yet unidentified (but statistically certain) impacts from the past.

CONTINENTS & TECTONIC PLATES

Some people have become understandably confused about the difference between a continent and a tectonic plate. Sometimes they seem to be the same thing. … sometimes not.

The Standard Theory isn't terribly useful here. It just lists as continents the seven standard land masses that we are taught in school and then shows a map of 12 primary tectonic plates, some of which relate to a single continent and some of which don't. The Standard Theory doesn't explain the relationship of continents and tectonic plates … it is what it is.

The Theory of Antipodal Impact Effects looks at the history of the continents and tectonic plates and tries to make sense of the way that they move and change.

When a continent is first uplifted, it rides on its own tectonic plate. The uplift frees it from most connection to other tectonic plates.

However, during the life of a continent, it can see many changes relating to its condition as a solo player on its own tectonic plate. South America and Africa are continents that survive today on their own tectonic plates.

However, some continents smash together (usually the ocean between them is subducted) and become a combined continent on a single tectonic plate. Examples of this include North America (which is a mixture of at least two continental masses) and Antarctica (Western Antarctica and Eastern Antarctica). Each of these pairs of combined continents share a tectonic plate.

The mega-combined continent of Eurasia has several continental masses (Siberia, India and many other continents that have captured and absorbed over the ages). Eurasia shares three major tectonic plates (the Eurasian plate, the Indian plate and a little bit of the North American plate which controls the eastern tail of Siberia, starting at the rift at lake Baikal).

The poor old Australian continent has been broken up into three different plates. There is the top half of the old Australian blob that is now in the Antarctica plate (as Eastern Antarctica), the bottom half of the old Australian blob in the Australian plate and the shattered remains of the Australian tail in the Philippines plate. One should also note that some of Australia's tail was stolen by the Indian continent during its uplifting and is now in the Indian plate.

Therefore, continents and plates start out as one and the same thing. However, as time goes by, that can change.


CONTINENTS, SUBCONTINENTS AND CRATONS

Another tricky concept is the difference between continents, subcontinents and cratons.

In this book, I recognize all land masses that were uplifted as a result of antipodal impact effects as continents. Therefore, I recognize Western Antarctica and India as continents They are small continents, but they are still continents, not hotspot islands.

The Standard Theory doesn't have a clear continental creation mechanism, and therefore, it does not have a clear definition of what a continent is or is not. Therefore, in accordance with the vague Standard Theory, many geologists refer to India as a subcontinent. They refer to Western Antarctica as just part of the Antarctica continent.

When I refer to India, I call it a continent, unless I am describing it specifically within the structure of the Standard Theory, when I refer to it as a subcontinent.

Cratons can be old uplifted sections of rock from, literally, eons ago. Many of these cratons are in excess of three billion years old. Many were uplifted when the lithosphere was thinner and continental uplift could occur from smaller impacts. Not surprisingly, continental uplift from smaller impacts often produced smaller "continents". Some of the cratons are no bigger than a good-sized island. But some of the cratons could be really big.

The common denominator involved with uplifted cratons is the concept that they are really old and the idea that many have been pulled back into the mantle as the subduction machine pulls new ocean floor from the mid-ocean ridge and subducts old cratons that don't get snared by the continent under which the old ocean floor is subducting.

This also means that probably all remaining old, uplifted cratons are now on land. Many of these remaining old cratons were part of an ocean floor that was uplifted as part of a new continent many years ago.

However, there are still some more recent flow basalt cratons out under the sea, such as the Kerguelen Plateau in the southern Indian Ocean. 40

A craton can also be used as a term describing a very large old area of stable rock at a continent's core (a core that is, in reality, a combination of smaller cratons). I am using the word craton in its smaller sense. South America and Africa are good examples of continents that are studded with old cratons. This studded structure is probably what the sea floor looked like when those continents were uplifted. 42