Following is the summary of my post and its follow up in the sci.geo.geology newsgroup from 08/22/2000 to 09/19/2000 under the subject name of "Unresolved part of the Plate Tectonics". I have listed most of the comments and my responses with additional information for the clarity.
Initial post on 08/22/2000
This post is related to snowball earth, ice ages, global warming, mass extinction, plate tectonics and Statics, a study of rigid body mechanics.
What happens when continents collide?
We are always looking at the sun as a major cause for the global climate change on the earth and literally ignoring the source of heat within the earth. We all know that earth is gradually cooling from its formation and plate tectonics is providing a controlled environment for the gradual cooling. Heat within the earth is being dissipated through the ridges and hot spots and keeps the environment warm on the surface. At this point we also know what happens when the plate tectonics stops on the earth, a global ice age covering all the surface of the earth. It is evident that plate tectonics can drastically change the global climate than the intensity of the sun.
Even though plate tectonics originated few decades ago we are still debating its functionality. At present we are of the assumption that plate tectonics works continuously as it is today and because of this conclusion we are eliminating the role of plate tectonics in controlling the global climate. When we are not sure of how the plate tectonics works (ridge push or slab pull?) then the conclusion about it's continuity is baseless.
A new hypothesis explains the whole functionality of the plate tectonics using the Statics, a study of the rigid body mechanics. This hypothesis uses the basic principles of Statics to explain the plate movements at the subduction zone. Formation of folded mountains at the subduction zone slows the subduction rate and eventually stops the movement of the subducting plate. When all the continents were collided to form the Supercontinent, folded mountains in the interior of the Supercontinent slowed the movement of the plates. Slow movement of the plate releases less magma at the ridge and cools the ocean. When the plates stopped moving in the Supercontinental formation, magma within the ridges seals the plates and forms as a single plate covering all the surface of the earth. This triggers a global ice age on the Supercontinent and some times forms as a snowball earth event. Breakup of the Supercontinent creates the new plates and ejects the magma onto the ice sheets melting them rapidly in a severe global warming. Formation of a new ridge causes the global warming and collision of the continents causes the ice age. Mass extinction happens in these global warming and ice age periods. This hypothesis not only uses the basics to explain the physical phenomena on the earth, but also creates an environment to study the earth as a single system by combining most of the branches in earth sciences.
Finally a word about the peer review. I did send this paper to some journals but they returned it stating that the subject is out of their coverage area. The multi disciplinary and theoretical nature of this hypothesis may not be suitable for any journal. Instead of keep trying for other journals I have posted this hypothesis on my home page. Please find the complete hypothesis at http://www.geocities.com/karunakarm/TectonicPause.html. This hypothesis could be right or wrong. I hope this post initiates some discussion on this subject.
Comment: We can see evidence of plate tectonics in rocks 2.7 billion years old; we can see evidence of it in earthquakes today; and we can see evidence in rocks of all ages between. What is baseless about that?
Response: I am not objecting to the concept of plate tectonics, my point is about its continuity. There wouldn't be any ridge or subduction zone in the Supercontinental period.
Comment: Which Supercontinent formed with a global ice age?
Response: This hypothesis uses the Statics to show how the plates move around between two Supercontinental formations. Each Supercontinent forms in the collision of all the continents. If a colliding continent is not going to stop, folded mountains continues to raise and the continental crust will shrink. But this is not the case in the history. Folded mountains while the Pangaea was formed stopped at some point and later Supercontinent broke up creating new plates. Any moving object to reverse its direction on the same line, it has to stop for a period at the end point. Try driving a car and reverse its direction without stopping at the end point. This hypothesis explains the global glaciations on all the known Supercontinents and predicts on other Supercontinent formations.
Comment: If you do a heat balance for the Earth, less than 10% of its heat is lost by conduction through the crust, and 90% by formation and subduction of oceanic crust. Without active ridges, the Earth would heat up at quite an appreciable rate.
Response: Rate of seafloor spreading dynamically changes with the movement of the plates. The present 90% heat loss through the ridges may be different in the past and may change in the future. Accumulation of the heat within the earth makes the hotsopts more active and massive eruption will take place in the Supercontinental period. Massive Siberian eruptions in the period of Pangaea may be the cause of the closed ridges. Because we have ridges at present, we are not seeing continuous activity in these hot spots. The accumulated heat itself is one of the cause for the breakup of the Supercontinent.
Comment: Large continents near poles tend to cool down more easily than open seas at the poles. High orogens prevent moist and warm winds to enter the regions behind (e.g. Tibet).
Additional Info: Position of the continents may control the extent of the glaciation but the orogen is not the basic cause for the ice ages. Occurrence of ice ages with the orogen is true but the cause is the reduced sea floor spreading at the end of the subducting plate, not the uplift of the mountains. Himalayas are still existing at the same place and even being uplifted further without causing any ice age. In fact we are experiencing the global warming in the present period.
Comment: Pangaea was ringed by subduction zones. Do you think plate boundaries just disappeared because of a Supercontinent?
Response: Continental collision merges the plates to form the super landmass and the breakup of the super landmass creates the new plates and new ridges. It is not possible to have ridges on the both ends of the plate, except in the case of the center plate like Africa. In between the collision and the breakup, oceanic ridges have to be closed. This is what I termed as a "tectonic pause" and the reduced seafloor spreading causes a global ice age or sometimes as snowball earth event. New ridges will form right in the middle of Supercontinent.
Comment: Subduction zones that have been incorporated into a Supercontinent are gone. But the subduction zones outside the Supercontinent are not affected by its formation.
Response: I don’t think we were left with any other subduction zones outside the Supercontinent after it's formation. Continents or plates were moving towards one place and the other side of the plates will have the ridges. Oceanic crust follows the continent while forming the Supercontinent. Supercontinental breakup detaches the oceanic crust at the continental margin and forms as a trench. New ridges form in the middle of the Supercontinent and plates slide on to the oceanic crust with a trench migration. When the next Supercontinent forms, we will be left with only the mid-Atlantic ridge encircling the next Supercontinent. When the subduction stops, the ridges will also close resulting a global ice age. (also see the next comment).
Comment: Why do you think the Atlantic will continue to widen? Doesn't it seem more likely that the cold oceanic crust along the eastern edge of N. America is more likely to break and begin subduction under the N. American plate. In essence creating two plates where before there was one.
Response: Even then, in the initial stages of the subduction, North America will slide on the newly formed plate, shrinking the pacific further. When there are two subduction zones on both sides of the ridge, there is a possibility that eventually the two plates will disappear joining the two continental land masses. Ridge will expand the ocean only when there are no subduction zones on either sides of the continental margins, like the mid-Atlantic ridge.
Additional Info: I misunderstood the comment and assumed the subduction on the west side of N. America instead of east. In reality the comment is correct. New ridge forms on the west side of the Americas and the continents reverse their direction of movement. New ridges will close after the formation of the Supercontinent.
Severity in the global climate change: Plate tectonics is not an independent entity.
It effects the global climate in a major way. The broadest climate variation on the
earth is the Supercontinental cycle. Every Supercontinent forms with a global ice
age. Next to it is the collision of individual plates. Every collision and the subsequent
ceasing of the subduction reduces the ridge length and causes a small scale ice age,
reducing the sea level. Breakup and formation of a new ridge increases the ridge length and thaws the environment
with a global warming. Melting ice sheets increases the sea level and floods the continental regions. Subsequent
global warming and the ice ages forms distinct era in the sedimentary layers. All the mass extinctions can be
traced to these global warming and ice age periods. I believe K-T boundary was formed in the breakup of the India from Africa 65 million years ago and the associated global warming might have caused the extinction of the dinosaurs.
The last effect on the global climate is the intensity of the sun and it’s cycles.
Because of these facts I said earth is a system, every phenomena is linked to each other and the plate tectonics is the life of the planet. The concept of continuity in the plate tectonics guided the earth sciences in wrong direction. My hypothesis not only completes the understanding of the plate tectonics, but also unifies all the physical phenomena on earth and explains the ice ages, global warming and mass extinctions. None of the existing theories explains these many facts of the earth in an unified way.
Comment: It's true that new ridge forms right in the middle of the Supercontinent. Why not the subduction zones forms on the margins of the Supercontinent?
Response: That's what the whole idea is about. Supercontinent breaks up forming the new ridges and subduction zones forms at the margins of the Supercontinent. This starts the new tectonic activity and continents starts to disperse with a trench migration.
This new tectonic activity increases the total ridge length and warms the environment in a severe global warming. Global warming melts the ice sheets and increases the sea level. This is what happened in the breakup of the Pangaea. The two known snowball earth events also happened on the Supercontinents and the breakup of those Supercontinents thawed the global ice ages.
My conclusion is super land masses or bigger plates will have reduced tectonic activity and smaller ridge length. When the continental crust forms as a single landmass tectonic activity stops. This could be very short period, but sufficient to cool the ocean and spreads as a global ice age and reduces the sea level, exposing the continental shelves. This is what I termed as the tectonic pause. This is where the Permian extinction was happened causing 90% of species to disappear.
Comment: Which is the cause for the plate movements, ridge push or slab pull?
Response: Ridge pushing for the cause of plate tectonics is the initial idea. Because there is no obstruction for the ridges in ocean, it might have generated the thought of continuity of plate tectonics. When subduction initiates at the trench, slab pulls the plate towards the trench. When subduction stops with the buildup of the folded mountains, ridge also closes in the ocean. Reduction in the total ridge length releases less magma into the oceans and cools the ocean water. Cold ocean starts to freeze from the poles and starts an ice age. When a new ridge forms, adds more magma into the ocean and thaws the ocean, melting the ice in a global warming. Total magma outflow into the ocean depends on the total ridge length and on the speed of the plates. Fast moving plates also releases more magma into the ocean and can melt the ice at the poles. Slow moving plates also can cause a small scale ice age without any reduction in the ridge length. Variations in the intensity of the sun can also be a cause for the global warming and ice ages independent of the affect of the plate tectonics.
Comment: There were massive eruptions in the Supercontinental period. How can you say that tectonics was ceasing then?
Response: Volcanic eruptions
(hotspots or plumes) are not part of the ridges, even though they are related to the ridges in different way. Heat within the earth always looks for a way out either through the ridges or through the volcanoes. Ridge provides an easy way for the escape of the heat than the volcanoes. Reduction in the ridge length (or less number of plates) or the reduced speed of the plates makes the volcanoes more active to make an alternative way out for the heat in the earth. Reduced ridge length and the slow movement of the plates caused the
end-Permian volcanic eruptions. The rate of heat loss not at all constant, it varies with the number of plates. More plates or more cracks in the crust will have higher rate of heat loss and less number of plates will have less heat loss through the ridges. When earth’s crust forms as a single plate, total heat loss will be only through the volcanoes.
Volcanoes can't substitute the ridges in the rate of heat loss, so heat builds up in the mantle and breaks the Supercontinental crust..
Comment: What about the most recent Ice Age: Would you say that tectonics is pausing during the last 2 Ma?
Response: I didn’t said every ice age will have a tectonic pause. Small scale ice ages are the result of collision between two plates. Tectonic pause talks about the collision of all the plates. Reduction in the speed of the Indian plate reduced the rate of sea floor spreading and caused the recent ice age. Closed ridges on the west coast of the North America which formed the faults might have also caused different ice ages.
Comment: As regards the separation of India: wasn't the creation of the Atlantic during the Jurassic much greater a volcanic event than the splitting off of India? Apart from this: there were many other species that went extinct at the K-T boundary. Would you relate all this to global warming? I agree that there is still no theory about the K-T event that all scientists subscribe to.
Response: As I mentioned earlier, speed of the plate also a cause for the global warming. New ridge and the fast movement of the India might have caused a severe global warming and the mass extinction. Every new ridge causes a global warming and mass extinction. The severity depends on the length of the new ridge and the speed of the plate.
Additional Info: Even the formation of the Atlantic also witnessed much greater mass extinction than the extinction at the K-T boundary. Which ever species adapts to the climate change survives and all others face the extinction.
Comment: Can this hypothesis stand for further tests?
Response: I believe there is undeniable truth behind this hypothesis. I am not opposing any existing major theories or facts, only filling the missing piece in the puzzle to make it clear what the puzzle is about. I have used the latest research with very basics to formulate my hypothesis.
Comment: Sun is the major cause for the climate change on the Earth and the expansion is the cause for the plate movements.
Response: My hypothesis is totally confined to plate tectonics and its effect on global climate variations. I never said that there were no other factors effects the global climate. In my initial post, I said my hypothesis could be right or wrong.
In concise my hypothesis says that large land masses will have reduced tectonic activity and it is possible that a single land mass will have nil activity with a tectonic pause. This causes the global ice age and reduces the sea level resulting a mass extinction. Breakup of the Supercontinent thaws the ice age.
Look at the following facts:
How the solar intensity can cause such an extreme variations in the earth's climate? Remember a fact that solar intensity is increasing with time from the formation of the earth. Also explain how the curvature of the rigid plates is changing with the expanding earth. If the earth expanded 55-65% from its initial breakup to the present size, the plates or the continents will look like inverted half spheres on the surface of the earth. In the case of Eurasia, even this is not possible without breaking it, because it encompasses the small earth of the expansion model. Expansion model doesn’t propose any breakup of the Eurasia from its initial formation then how did it spread on the expanded globe. One more thing, if the expansion of the earth is true, it is not a big deal to incorporate this feature of the earth into the theory of plate tectonics and the Supercontinent cycle. To spread the spherical objects on the surface of the expanding globe, we need to make them into pieces and then reassemble them on the surface with less curvature. If the theory is true, it may be one of the reasons driving the Supercontinent cycle, which restructures the continental crust. When I was working on my hypothesis, I faced with a problem. Ice covered Supercontinent becomes heavier and sinks into the mantle. Lighter oceanic crust bulges out and solidifies. Later addition of water onto the oceanic crust will not shrink the rigid crust and as a result earth will expand between each Supercontinent cycle. I thought this is not possible, that’s why I didn’t touch that part. If the bulge in the lighter oceanic crust is possible, expansion is already there in the Supercontinental cycle of the plate tectonics. If at all the earth is expanding, that should be a gradual change from the formation of the earth and Supercontinental cycle may be providing a mechanism for that expansion, without gaining any mass. You can’t explain all the physical phenomena with just the expansion theory. Plate tectonics is the only way to explain the physical phenomena and as I mentioned earlier, if the expansion is true (with or without a gain in the mass) it can be easily incorporated into the plate tectonics.
Comment: I was under the impression that the global climate was particularly warm during the Permian, hence extensive Permian red sandstone deposits. Is this correct?
Response: Pangaea need not form completely to reduce the sea level. Sea level reduces step by step, when continents collide one after the other to form the Pangaea. When Permian extinction happened there might be a collision of bigger landmasses. This closes a major part of the ridge and cools the ocean, spreads the ice age on the continental landmass. this removal of water from the ocean reduces the sea level.
Additional Info: Even though most of the Permian age was under icehouse environment, end Permian was a hothouse environment. Mass extinction in the Permian was initiated by the global cooling and terminated with the global warming caused by the breakup of the Pangaea.
Comment: In support of continuity -
- When a subduction zone closes new oness form in the crust.
- There are plenty of reasons for the coontinuity of plate tectonics.. paleomagnetism provides most of them.
- Subduction doesn't stop on the planet,, it moves elsewhere once it stops at a place.
- Rate of sea floor spreading can changee.
Response: Present belief is plate tectonics works the same way as it is present. This assumption made the crustal breakup an uneventful episode. Nobody gave any importance even to the Supercontinental breakup because of the continuity in plate tectonics. That means the belief is sea floor spreading is more or less same all the time. When variable rate of spreading is possible, what are the objections for the minimum or nil sea floor spreading. Minimum seafloor spreading is very much possible in the Supercontinental period. Nil spreading, a tectonic pause, is a discontinuity in the plate tectonics. Yes, subduction moves from the interior to the exterior of the Supercontinent and this is not an instantaneous shift. In geological time scales it should take at least few million years and that is sufficient to form an ice age. You need to accept the fact that the continuity is just a belief without any base. Major restructuring of plates happens in the Supercontinental period, old plates merges together and new plates will be created. The period in between these two episodes is a discontinuity in plate tectonics. Supercontinental ice ages, mass extinctions and the subsequent evolution after the global warming are proof to the discontinuity in plate tectonics.
Explanation of the hypothesis: The fact and simplicity of my hypothesis is our current advancement in the plate tectonics really tells about the Supercontinental tectonic pause, but at present we are unable to realize this fact. Solar intensity was increasing with time and the sun was very faint in the early stages of the earth history. Global ice ages were spread near to the equator and they abruptly ended even in that early period of earth. All the four known Supercontinents has indications of the global ice ages. The abrupt exit of these global ice ages can only be associated with the plate tectonics. Severity in the global ice age might be reducing because of the increase in the solar intensity.
Supercontinents and global ice ages:
There should be at least three more Supercontinents with possible snowball earth events in between 800-2400 ma. We never looked at the Supercontinents with view of global ice ages on them. In future, we may find these two events together in the above mentioned period. Out of seven possible Supercontinents in the whole history of the earth we know four and all four are associated with the global ice ages. Supercontinental global ice ages are the result of tectonic process, neither an accidental coincidence nor the result of any other process.
A look at the current theories for the snowball event:
Green house gas theory says that decrease in the content of green house gases caused the earth to freeze and the increase thawed the ice age. Slow accumulation of green house gases can’t cause the sudden melting of the ice sheets and more over if we go back in the history, when the sun was very faint, we need massive amounts of green house gases and prolonged period of heating. This theory ignored the very volcanism (including the ridge activity) that generated the green house gases just because of the concept of continuity in plate tectonics.
Another explanation is to change the tilt of the earth axis so that the present equatorial regions to be at the present poles. This change in the tilt makes the present polar regions free of ice, but even the polar regions also experienced the glaciations in the snowball period. This theory doesn’t provide the mechanism for changing the tilt and also it is difficult to explain successive ice ages in a short period.
When we don’t have the data we need to fill the gap interpreting the facts with the present knowledge of science. I have used the basic principles of rigid body mechanics (Statics) and the present understanding of plate tectonics to show how the subduction stops when mountains build up at the subduction zone and finally concluded that at one point of time there will be a tectonic pause with very minimum or zero rate of sea floor spreading on the Supercontinental crust.
Because of the preceding tectonic pause and pressure buildup in the mantle Supercontinental breakup will be an explosive and violent event. Newly formed open ridges on the Supercontinent spews massive amounts of green house gases, outpours the magma onto the ice covered continental crust and rapidly melts the ice sheets exiting the snowball earth event. I believe the major boundaries in the sedimentary layers are the result of formation of new ridges and the collision of continents. These boundaries can be linked to major mass extinctions in the history of earth. This hypothesis also helps in the search for extraterrestrial life. Plate tectonics is crucial for the survival of life on the planet or satellite. When we realize the fact that the global ice age or the snowball event as part of the plate tectonics and later if we find any extra terrestrial object with traces of plate tectonics and massive ice sheets, we can assume that the object is in a Supercontinental tectonic pause. Jovian moons (Io, Europa) may yield some clues to these facts.
A review of the continuity in plate tectonics: If we believe in the constant rate of sea floor spreading, according to the concept of continuity in plate tectonics, earth will expand when the subduction stops in the Supercontinent formation. This is totally opposite to plate tectonics and an open support to the expansion earth theory. Continuity is not valid in the present context of the plate tectonics, where we believe in the subduction as the cause for the plate movements. Expansion earth theorists believe in the continuous existence of the mid ocean ridges from the initial breakup of the crust. It is not possible for the expansion theory to propose the cessation of the ridge activity. Continuity in the sea floor spreading is the basis for the expansion theory. Fixed earth and the Supercontinent cycle can only be explained by the variable rate of sea floor spreading.
Rate of sea floor spreading depends upon the total length of the ridge and the speed of the plates. When the subduction stops at the trench, the associated ridge closes and reduces the rate of sea floor spreading. When all the subduction zones stops in the Supercontinental formation, major ridge system closes and drastically reduces the sea floor spreading, sometimes to zero in a tectonic pause. Reduced sea floor spreading merges all the plates and causes the global ice age on the Supercontinent. Supercontinental breakup creates the new plates with a severe global warming and thaws the global ice age. In the same way, each new ridge causes a global warming and each collision causes an ice age. The resulting decrease and increase in the sea level creates the sedimentary layers. All the mass extinctions can be traced to these global warming and ice age periods.
A look at the present state of earth sciences because of the false concept of continuity
Unresolved part of the Plate Tectonics.
At present we have pretty much knowledge of plate tectonics about how it is reshaping the surface of the earth. Even though both ridges and trenches are part of plate movements, much of the data about the plate mechanics will be recorded around the ridges. Continuous recycle of the oceanic crust erases much of this data and we will be left with very limited data to interpret the past movement of the plates. In the absence of complete data, all the conclusions about the past history of the earth are questionable. In this scenario the latest developments in plate tectonics and the concept of continuity appears to be mutually exclusive. When I applied these latest developments to the past history, plate tectonics revealed another kind of data in the form of ice ages right on the surface of the continents. All the known past history of the earth can be explained in a unified way using the concept of discontinuity in plate tectonics. The real test for the hypothesis is in the future findings about the other Supercontinent formations. Ultimately the unresolved part of plate tectonics may evolve as the tectonic pause or it could even dissolve into the continuity.
My intension in mentioning the peer review was to tell everybody not to ignore this post just because it was not peer reviewed. Quality research can be in any form and can come from any source.
I was basically concentrated in replying to the critical comments of the hypothesis and might have not responded in time to the other posts. My thanks to everybody participated in the discussion and hope something concrete will shape out of this discussion in the future.
I started posting in the newsgroups from the day I published my hypothesis on my site. But this is the only thread which had much extensive discussion among all of my posts.
This page posted on: 11th March, 2001.
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