Prologue: Sometime ago I published a 3-part diary series on the Colorado Plateau (if interested in reading this diary, see this URL to get started: http://www.dailykos.com/...). Given that broad subject matter I mentioned the why and how (and for the most part, the when factor) process of Colorado Plateau's uplifting event. Specifically, how its province was directly related to plate tectonics, the same as happens with mountain-building, volcanic activity, and earthquakes. What follows in this diary will focus on this subject matter––plate tectonics––and provide the reader with a concise, though nonetheless, generalized comprehension of this subject matter. Let's just call it a crash course on the collision of continental and oceanic plates. Ongoing, by the way.
As most of us already know, continents move around the globe and slide on the rigid outer part of the Earth, whose rind consists of the crust and upper mantle. Think of these migrating plates as large, stable blocks of the crust forming the nucleus of a continent (also known as “craton”). Another way to think of this scenario is to envision a series of planetary plates as continental “rafts” inexorably inching along the lithosphere (the crust and upper mantle) but at a remarkably slow pace. Because continents and oceanic plates move, fender-bender incidents (or worse) are unavoidable. Hence, think of these plate encounters as extremely slow-moving traffic in motion, whose geophysical process accounts for the planet constantly rearranging its granitic and basaltic furnishings (respectively, continental and oceanic material).
As you can see from the picture, look at a globe or a map of the Earth and it’s easy to see which landmass crustal pieces fit where (at one time), then discern how that greater geophysical force tore these landmasses apart. We’re talking hundreds of millions of years, and likely billions, in the overall process of changing plates. Thus this science discourages adamant parochial views based on a much smaller figure given the age of our planet, say, the 6,000 or so year figure some denominations consider more realistic.
Linked Landmasses In The Past: Today, most people accept the fact our planet is a restive geophysical process serving up sporadic earthquakes, mountain-building and volcanic activity. There was a time, however, when just about everyone took it for granted how the arrangement of the Earth’s landmasses were always in the position we see and realize today. Thus a fixed arrangement, as though the planet was in stasis. Actually, hundreds of millions of years ago the terrestrial scene was one huge supercontinent and one world ocean surrounding its landmass. Geologists coin a word for this phenomenon––Pangea––meaning (in a literal sense) "one world." Sometimes spelled “Pangaea” or “Pangaea”, the origins of this somewhat flamboyant word comes from the ancient Greek “pan,” meaning “entire” and “Earth” (from the Latinized ‘Gaea’).
As a consequence of Pangea’s great landmass breakup millions of years ago, its once fused plate broke up into a secondary, though nonetheless, huge tract of land called Laurasia, which later evolved into what we now call the North American and Eurasia continents. The other equally large tract was called Gondwana (sometimes spelled “Gondwanaland). From there, both somewhat downsized continental masses fragmented into a variety of continents, such as depicted on today's global maps.
Before examining this subject matter further, the above-mentioned “plates” has to be explained to make sure we're all on the same page given the ensuing explanation. To be exact, both continental and oceanic crustal plates.
Once Pangea broke up those plates were all set free, or most of them were. And by free, I mean wandering around the globe, as though individual bumper cars in an amusement park. (I may have just dated my own antiquity by mentioning this jarring amusement park ride, though in a way I think of plate masses moving hither and yon and eventually running into one another, thereby simulating bumper cars. Or something.) Of course, plates, once separated from a greater mass, slid along the lithosphere, and likely driven by an internal force that has taken this long for the present-day arrangement of landmass assembly. Millions of years from now a new “one world” motif will likely form once more. Indeed, before Pangea there were other supercontinents, almost from the beginning of time. (All of the finer details, of course, will follow later in this diary, as well as tomorrow's finale and explanation.)
For now, I can promise you even if you’re not normally interested in science this subject matter should keep you awake. In fact, everything having to do with earthquakes, volcanic eruptions, even tsunamis, is traced to our constantly changing planet and greater internal forces welling from the nether world. This means things are sort of heating up, in a manner of speaking, because we are seeing more geophysical activity compared to the fairly recent past. Consider the plight of, say, Japan, that is presently getting a lot of shake, rattle and roll flurry, all because her continental mass is being encroached upon by two huge plates, a sort of squeeze play if you will.
For Japan these days, the plate activity scene looks like this:
Plate Tectonics: It sounds like a French du jour meal is being served, but I assure you the origins of the word, “tectonic,” is Greek (so think "feta, "ouzo," and "mezethes" instead). Tectonic literally means “builder” or “mason,” and some geologists might even use “carpenter” to describe such activity. Simply put, plate tectonics describes what is and has taken place on the lithosphere. The concept was brought to light by Alfred Wegener. His novel idea in the early part of the 20th century encompasses the older concept of “continental drift.”
Later, in the 1960s, when seafloor spreading was a vogue science plate tectonics was embraced and Wegener’s earlier ideas were finally validated by the scientific community. It is also interesting to note how the oldest seafloor averages some 170 million years old, and 200 million is more the average. Compare this young figure to the oldest bit of continental crust that goes back as far as 4 billion years (or more).
Suffice it to say, in his day Wegener, a climatologist by trade (mostly that) was thought of as somewhat of an eccentric (or madman) for even suggesting the idea of wandering global plates. However, many decades later he took a bow (had he lived that long) and likely thumbed his nose at such close-minded critics!
Note: Wegener was empirical given his ideas as he was following in the steps of learned others who proposed a similar idea much earlier. For instance, Abraham Ortelius (in 1596), Theodor Christoph Lilienthal (in 1756), Alexander von Humbolt (in 1801 and again in 1845), Antonio Snider-Pellegrini (in 1858), and some few obscure others who had noted the distinctive shapes of continents on opposite sides of the Atlantic Ocean (i.e., Africa and South America) and how these land ‘pieces’ seemed to fit together.These days it's obvious how tectonic plates move around the world, some going this way, others that way, and still others glued in position (i.e., Antarctica) and literally grounded. We also understand more of the Earth's geophysical dynamics and how its specific crustal layers work to the advantage of moving plates. Consider the outermost part of its interior which is made up of two distinct layers: the aforementioned lithosphere and the asthenosphere that lies directly below. Although solid, the asthenosphere has a relatively low viscosity and shear strength. It also flows like a molten liquid over billions of years. The deepest part of the mantle (below the asthenosphere) is even more rigid due to the extreme higher pressure. But it is the lithosphere we are mainly interested in given the view of tectonic plates sliding around on its surface (and let's switch from bumper cars to rafts since more people understand how easily rafts vector along the surface of water, except we're talking about a lithosphere, not water).
This brings us to a tally of plates: there are eight major plates and scores of minor plates that make up the whole. All lithospheric plates ride on top of the asthenosphere and each plate moves in relation to one another at one of three types of plate boundaries: CONVERGENT (or collisional boundaries); DIVERGENT (or spreading centers); and TRANSFORM (see below for a brief description of each)
What happens at such boundaries? I mentioned this fact before: earthquakes, volcanic, mountain-building, and oceanic trench activity. How fast is the lateral movement of the plates? Typically, 1.9 to 3.9 inches a year. That’s not a lot of movement in one sense, yet over billions of years it adds up to a lot of distance covered.
Note: a convergent boundary, also known as a destructive plate boundary (i.e., due to a secondary activity called "plate subduction"), is an actively deforming region where two (or more) tectonic plates or fragments of lithosphere move toward one another and collide. A divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature existing between two tectonic plates that are moving away from each other. A transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either a sinistral (the left side) or dextral (the right side) direction. Furthermore, transform faults end abruptly and are connected on both ends to other faults, ridges, or subduction zones. These terms will be explained in more detail further along in this diary series.The Science Of A Seeming Daft Man: In Wegener’s work, “The Origin of Continents and Oceans” (1915, the expanded version), he boldly suggested to fellow scientists how the present continents once formed a single land mass that eventually drifted apart. He likened the picture to icebergs of low density (granitic) floating on a sea of much denser basalt. His peers (and those outside his science) thought him mad to propose such an idea. For one thing, it didn’t seem to anyone else in Wegener’s time how portions of the crust could move around like floating icebergs of granite. A solid crust and liquid core was one thing, but icebergs on top and riding on the surface? Nicht! Nach Hause gehen, Herr Wegener!
However, in 1928 Wegener was not easily persuaded to give up his theory by giving in to his critics. Instead, he was adamant given his theories and had found an ally who added something else to the continental drift theory. Arthur Holmes, an English geologist, was the man who saved Wegener’s speck (we call it bacon). Holmes also took a closer look at plate junctions beneath the sea. He then suggested convection currents deep within the mantle act as the driving force for whatever is on top (of the lithosphere).
Still, the idea of moving plates accounting for the global map of Wegener's time was a quiet or dead subject in most scientific circles.
By the mid-1950s, however, a variable magnetic field direction in rocks dated from differing ages added collaboration and evidence to what Wegener and Holmes came up with, both acting on independent information and observation. The expansion of the global crust accounted for the magnetic field reversals and seafloor spreading because of the new rock upwelling evidence. That was precisely the geophysical force behind the growing plate tectonic movement.
Then, in the 1960s, seismic imaging techniques were introduced, as well as consequential studies of the deep ocean floor mapping. All told, the evidence confirmed what Wegener had conceived and believed in to the day he died. His idea, combined with all the others who worked to either prove or disprove his theory, revolutionized the earth sciences. Finally, there was an empirical way to explain a diverse range of geological phenomena. Paleogeography and paleobiology were in full swing, as scientific disciplines that enriched the earth sciences.
Note: Mechanically, the lithosphere is relatively much cooler and more rigid compared to the hotter asthenosphere, which also flows more easily. Consequently, the lithosphere loses heat by conduction whereas the asthenosphere transfers its heat by convection. The crux of plate tectonics comes down to this point: The lithosphere exists as separate and distinct tectonic plates riding on the visco-elastic solid asthenosphere (which is more fluid). Tectonic plates also consist of lithospheric mantle overlain by oceanic SIMA crust (from silicon and magnesium elements) and continental SIAL crust (from silicon and aluminum). The average thickness of the oceanic lithosphere is about 60 miles. Over time it conductively cools and becomes thicker. Because the oceanic lithosphere travels, its mass eventually is subducted. Typical continental lithosphere material is 120 miles thick. Tectonic plates can therefore include continental crust or oceanic crust. In fact, many contain both elements (i.e., the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans). Another distinction between the two is that oceanic crust is formed at seafloor spreading centers, while continental crust is formed through arc volcanism and accretion of terranes through tectonic processes. Notably, oceanic crust is denser than continental crust due to their respective compositions. Oceanic crust is also denser because it has less silicon and has more of the heavier elements (i.e., “mafic”) than continental crust (i.e., “felsic”). In other words, because of this density stratification oceanic crust usually lies below sea level, while the continental crust buoyantly projects itself above sea level (a process known as “isostasy”).Now you know a lot more about why the planet is continually changing in often and seeming violent ways, and why some of the more cataclysmic events are, so to speak, earth-shaking. If you could live for, say, a few hundred or so million years the one plus notion I can think of is that you won’t have to go anywhere to see the world: it’s coming to you whether you like it or not, all because plates move around the globe.
• African Plate covering Africa - Continental plateThe Intricacies Of The Supercontinents: Previously mentioned was how Pangea, as a supercontinent landmass, whose previous primal state was slowly and surely been coalesced from many different migrating landmass fragments. In this sense, think of the world that was at one time one gigantic single plate. To be more precise, once the planet’s crust had formed and accretion was underway (i.e., bits and pieces cobbled together to form continental plates) the Earth was cool enough to turn solid in places.
• Antarctic Plate covering Antarctica - Continental plate
• Australian Plate covering Australia - Continental plate
• Indian Plate covering Indian subcontinent and a part of Indian Ocean –Continental plate
• Eurasian Plate covering Asia and Europe - Continental plate
• North American Plate covering North America and north-east Siberia - Continental plate
• South American Plate covering South America - Continental plate
• Pacific Plate covering the Pacific Ocean - Oceanic plate
Notable minor plates include:
The Arabian Plate, the Caribbean Plate, the Juan de Fuca Plate, the Cocos Plate, the Nazca Plate, the Philippine Plate and the Scotia Plate. Add to these minor plates the dozens of tertiary plates that are grouped with larger plates. For instance, associated with the African Plate are the Madagascar, Nubian, Seychelles and Somali plates.
It follows how the initial crust that had formed billions of years ago had disappeared during the so-called Hadean phase of the planet’s forming due to a combination of faster-moving Hadean plate tectonics, as well as primordial and intense impacts of a heavy bombardment of material from outer space. The crust at this time might also have been basaltic in composition similar to today’s oceanic crust.
Note: Hadean, sometimes spelled “Hadeon,” derives from “Hades,” the Greek name for the god of the underworld. Hence, a hellish time on the planet, some 4.4 to 4.6 billion years ago (depending on which figure you accept as the oldest age of the planet).
Given the above explanation, geologists believe the first larger pieces of continental crust caused by a product of differentiation of lighter elements during partial melting phases in the lower crust appeared at the start of the Archaean Eon, some 3.9 or 4.0 billion years ago. What remains of these downsized portions of crust forms the cores around which today’s continents grew (and sometimes diminished in size).
Note: Naturally, during the planet's primordial time there were plate collisions occurring at various times, which created fewer and larger continental fragments. While continental plate collisions created fewer and larger continental pieces, the so-called “rifting” occurrences created more, though smaller, continental fragments.The other thing about supercontinents is that they have a cycle that descries the quasi-periodic aggregation and dispersal of the planet’s continental crust. Some geologists think the crust is increasing, some think its decreasing, while others think the overall material is constant. What they do agree on, however, is the material is constantly being reconfigured (i.e., because plates are migratory). One complete supercontinent cycle is said to take some 300 to 500 million years to occur. However, Pangea’s cycle was on the lower side of this quantitative estimate.
A Likely Account Of Pangea's Forming: As a theorized (or conceptualized) supercontinent, Pangea formed its mega real estate during the latter part of the Paleozoic Era’s Permian Period some 225 million years ago (hereafter, “mya”). But its amalgamated land mass shield comprised of all the world’s continents began to break up relatively early in the Mesozoic Era’s Triassic Period (roughly, 200 mya), and therefore well into the Mesozoic Era. For a period of time there was also only one body of water surrounding this massive supercontinent, the Panthalassa Ocean.
As previously touched upon, the merging of the continental plates into a vast supercontinent appears to be a cyclical occurrence throughout much of the planet’s 4.4 to 4.6 billion year history, that is, when crustal land masses first formed. In time, continents of substantial size were on the move; gigantic and relatively smaller-sized crustal plates migrating around the globe, each fragment created from metamorphic and sedimentary materials, but mostly granite.
Earlier Supercontinent Before Pangea: Another major and consolidated landmass mentioned earlier, though without a name, was “Rodinia.” Its super sized estate formed sometime during the Proterozoic Eon (roughly, 2.5 billion years to 540 million years). However, its union of continents is not nearly as well understood compared to ensuing Pangea. Indeed, any suspected supercontinents prior to Rodinia are even more vague, though nevertheless still postulated.
Breakups In Continuum: It was sometime after Rodinia’s coming apart that relatively smaller supercontinents of Proto-Laurasia and Proto-Gondwana had formed, along with the smaller Congo craton. In time, Proto-Laurasia split apart to form the continents of Laurentia, Siberia and Baltica (which today the latter is known as Europe). The rifting also spawned two new oceans, the lapetus (never capitalized, by the way) and Khanty oceans. Somewhere around 600 mya most of these land masses came back together (again) and formed the supercontinent known as Pannotia. This melded estate of landmasses included large amounts of land near the North and South Poles, yet only a relatively small strip near the equator.
Then sometime during the Cambrian epoch, about 540 mya, Pannotia started to break up. Its undoing gave rise to the continents of Laurentia (today’s North America, or most of it), Baltica (Europe), and the southern supercontinent, Gondwana. At the time, Laurentia straddled the equator. There were also three bordering oceans, as well: the Panthalassic to the north and west; the lapetus ocean to the south and the Khanty to the east.
So, the global mass of continents at the time went from this:
To something like this:
Around 480 mya the microcontinent of “Avalonia” came into the picture. It was a landmass that eventually would make up the northeastern sector of the United States. Nova Scotia and England at this time also broke free from Gondwana and began their respective journeys to Laurentia. Continents can therefore grow or decrease in size, depending on the circumstances over millions of years.
Let's Take A Fast Ride In A Time Machine: The following overview denotes a jigsaw puzzle of the Earth’s changing body parts, it’s landmasses as it were. I also believe it is better to explain what’s happening over millions of years by stepping outside yourself, then fly with me in a time machine. This way we can watch the world’s landmass fragments come together only to drift apart again, creating a new floor plan in the mixup of its plats. For the demonstration, I'll borrow this nifty time machine model, so let's all cram the interior, this time going backward in time:
We begin by watching Baltica, Laurentia, and Avalonia form a compacted merger (a consolidated landmass). This event happens around the end of the Ordovician Period (roughly, 440 mya). At this time, there is also a minor supercontinent called Euraamerica (or “Laurussia” as it’s sometimes called) that formed and closed the lapetus Ocean. That collision later resulted in the formation of the northern Appalachian Mountains. Siberia was then located near Euramerica, with the Khanty Ocean between the two continents. Meanwhile, Gondwana drifted toward the South Pole. This event marks the first step toward the later formation of Pangea. The second step resulted when Gondwana collided with Euramerica. By the next period of the Paleozoic, called the Silurian, Baltica had already collided with Laurentia and formed Euramerica. But Avalonia was still apart from Laurentia and seaway between the two land masses, a remnant of the lapetus Ocean, was shrinking in size while Avalonia inched toward Laurentia.
I’m thinking two things at this point: 1) you get the picture puzzle scenario of the slow-paced changes that were occurring around the planet, and 2) some of you might be wondering “When’s lunch?” Well, the thing about geology and how geologists' theories work in subject matter like this comes down to one major point: To build a hypothesis you have to add a lot of detail. And details given how the world has arranged its furniture is really what it’s all about. Namely, a dynamic and fascinating rearrangement pattern that may be here today and look this or that way, but sometime in the future will be dramatically changed.
Continuing our journey back in time, during this ancient period the Earth’s oceans were shrinking, continents were growing larger, island arcs (i.e., a curved chain of volcanic islands located at a tectonic plate margin) split off from major continental shields, and were on direct collision courses with moving tectonic plates. New oceans, like the Ural and Rheic bodies of water, were forming in the process. Baltica (Europe) was part of Euramerica. By the late Silurian period, North and South China rifted away from Godwana and began a journey northward across the Proto-Tethys Ocean, which was also shrinking in size. Yet at its southern end the new Paleo-Tethys Ocean was opening. Then, in the Devonian Period, Godwana headed toward Euramerica and caused the Rheic Ocean to shrink. In the millions of years to follow, the pieces of the future Pangea were on the way––as a completed process––because that’s just how things work when plates come together, stick for a while, then like feuding families, split apart. In the interim, other continents (or pieces), like Northwest Africa, had touched the southeastern coast of Euramerica and created the southern portion of the Appalachian Mountains. South America moved northward to reach southern Euramerica. The eastern portion of Gondwana (India, Australia and Antarctica) headed toward the South Pole (from the equator).
As for today's China, its north and south sectors were located on independent continents. The Kazakhstania microcontinent had since collided with Siberia, which the latter had been a separate continent for millions of years since Pannotia broke apart. Later, Kazakhstania collided with Baltica and closed the Ural Ocean between them, also the western portion of the Proto-Tethys Ocean. Those events instigated the literal uprising of the Ural Mountains and the formation of Laurasia, thus marking the final step in the formation of Pangea.
Laurentia (that’s us here in North America, if you recall) was the key component of the landmass puzzle slowly coming together. By then, South America collided with Laurentia’s southern border and closed the Rheic Ocean. As for Gondwana’s huge parcel, it was positioned somewhere near the South Pole. Consequently glaciers formed in Antarctica, India, Australia, southern Africa and South America. The North China chunk of land collided with Siberia and completely closed the Proto-Tethys Ocean.
Now we’re closing in on the termination of the Paleozoic Era. This timeframe marks the Permian period. The Cimmerian plate (comprised of parts of present-day Anatolia, Iran, Afghanistan, Tibet, Indochina and Malaya regions) rifted away from Gondwana and migrated toward Laurasia. A new ocean had also formed in its southern axis, the Tethys. That event soon closed the Paleo-Tethys Ocean. For the most part, the land masses that previously migrated over the lithosphere had formed the supercontinent, Pangea. By the Triassic Period, Pangea had a slight rotation toward the southwest. The Paleo-Tethys Ocean had closed from west to east and created the Cimmerian Orogeny. The shape of Pangea looked more or less like the letter C, slightly off-center, with the ocean locked inside. This was the new Tethys Ocean.
Where’s The Proof, And Not The Beef? With the world’s plates acting like a giant’s jigsaw puzzle, thereby constantly rearranging itself, what is the evidence for such events? Using Pangea’s template as an example of how supercontinents are formed, the best evidence is found in fossil remains. Finding the presence of similar and identical species on continents that have since grown thousands of miles apart confirms a reliable and empirical match. Additionally, the geology of adjacent continents provides sound evidence for corroborating what used to be where but ended up somewhere else. This evidence includes matching geological trends between the eastern coast of, say, South America and the western cost of Africa. A more perfect match, as a fit, makes the point more than obvious. (This evidence is presented in more detail in tomorrow's diary.)
Aside from the fact all the major continents were once welded together, the polar ice cap prior to the close of the Paleozoic Era accounted for the southern end of Pangea. We have glacial deposits, notably till (unsorted glacial sediment) from the same age and structure that are found on many separate continents, and thereby provide evidence these now separate continents would have been grouped together.
As for how geologists are able to determine the movement of continental plates, the procedure is done by examining the orientation of magnetic minerals in rocks (called “fission tracks”). In short, when rocks are formed they take on the magnetic properties of the planet and indicate in which direction the poles lie relative to the rock specimen. Since the North and South Poles do not move more than a few degrees one way or the other, magnetic anomalies in rocks are explained by the drifting of continents.
Returning to the initial thesis of this diary, we have this point to keep in mind: If continents drift and eventually come together, then it follows they will split apart––eventually. On this note, geologists reason there were three major phases in the breakup of Pangea. The first phase happened in the Early to Middle Jurassic (roughly, 200 to 175 mya). At that time, Pangea created a rift from the Tethys Ocean in the east and the Pacific in the west. The rifting took place between North America and Africa. In the process, the rifting produced numerous “failed rifts” (where the sea water does not fill in the rift). The rift resulted in creating a new ocean, the Atlantic Ocean, which, itself, did not open uniformly. Its rifting began in the north-central sectors (of the Atlantic basin). The South Atlantic, however, did not open until the Cretaceous Period. Sometime during this period Laurasia began to rotate clockwise and moved northward with North America to the north. Eurasia was to the south. That clockwise motion (of Laurasia) eventually was the cause for closing the Tethys Ocean. During this new movement and change in progress new rifts on the other side of Africa formed, principally along the adjacent margins of East Africa, Antarctica and Madagascar. All this would eventually lead to the formation of the southwestern Indian Ocean.
The second major phase began sometime during the Early Cretaceous (150 - 140 mya). That event took place when the minor supercontinent of Gondwana separated into four individual continents: Africa, South America, India and Antarctica/Australia, which were still attached. About 200 mya the continent of Cimmeria collided with Eurasia. However, a subduction zone was forming, as soon as Cimmeria collided. There were lots of similar changes and events that took place in this time period. For instance, the continental landmarks South America and Africa separated from eastern Gondwana (i.e., Antarctica, India and Australia) and that event caused the opening of the South Indian Ocean. That happened in the early part of the Cretaceous. By the middle of the Cretaceous Gondwana fragmented to open up the entire South Atlantic Ocean and South America moved westward away from Africa. The rift of the Atlantic went from the south to the north and was not a uniform event. Madagascar and India separated from Antarctica and moved northward and opened up the Indian Ocean. In time, Madagascar and India separated from each other. Late in the Cretaceous (100 - 90 mya) India continued to move northward toward Eurasia and closed the Tethys Ocean. Madagascar, however, stopped moving and became locked to the African plate. Then, New Zealand, New Caledonia, and what was called Zealandia separated from Australia and moved eastward toward the Pacific. The Coral Sea and Tasman Sea were then opened.
The third and final phase of Pangea’s breakup occurred in the early Cenozoic (the Paleocene to Oligocene Periods). North America and Greenland (which were part of one another’s estate) broke free from Eurasia. The Norwegian Sea was then opened. Meanwhile, the Atlantic and Indian Oceans continued to expand. Check out this URL for an animated version how all three phases came about:
All the while these moving plates were on the move again Australia finally split from the Antarctica continent and moved northward. India had already migrated in that direction some 40 million years earlier. And what happened to that other part of Australia...present day’s Antarctica? Its huge estate was shuttled to the bottom of the world since the formation of Pangea some 280 mya. In time, some two miles of ice laid on top of the original subtropical environments (thus, a warm and dry climate that spawned all sorts of lifeforms, including dinosaurs). This aptly named ice continent will also forever remain pinned to the bottom of the world due to the Earth’s rotational centripetal force.
While these pieces of continents were breaking apart India, in its migration northward, started to collide with Asia (roughly, 35 mya). The meeting of the two plates formed the highest mountain range on the planet, the Himalayas. At the same time, the Tethys Seaway was finally closed. The collision occurs to the present day. The African Plate also started to change directions, moving from west to northwest toward Europe. South America was also affected by these changes. It’s continental slab began to move in a northward direction, which separated it from Antarctica. Consequently, Antarctica was completed surrounded by ocean water for the first time. As mentioned, Antarctica was also locked inside a frigid zone and the rapid cooling allowed glaciers to form. Other major events took place during the Cenozoic Era were the opening of the Gulf of California, the uplift of the Alps, and the opening of the Sea of Japan. Pangea’s breakup continues to this very day and can be seen in the Great Rift Valley (more commonly called the East African Rift. The rift is a geographic trough some 3,700 miles long and runs from northern Syria in Southwest Asia to central Mozambique in East Africa. This divergent plate boundary is in the process of splitting the African plate into two separate plates geologists refer to as the Nubian and Somalian sub-plates (or proto-plates).
So, from this depiction of our planet sometime before the end of the Paleozoic Era:
To today's continental arrangement:
You now have an empirical demonstration of what happened to our world over millions of time. . .and will continue for as long as there is moms, apple pies, and mother countries. Let us hope that other meaning of one world also kicks in a new paradigm for our continuing path to higher consciousness. Namaste!
Well, that’s about enough of this first diary’s import and I’ll be back tomorrow with the conclusion. I’m also thinking some of you never knew there was so much background covering this subject (and neither did I know it many years ago until I got curious enough to know how I could stay in one place and bring some other faraway place close to me, even encroaching my turf. . .bad joke, I know). Anyway, for those of you who want to be geologists, but know your present job pays better, at least you can understand some of what these rock heads do for a living. So, it’s not always about shale oil stuff, which admittedly pays more money.
Note: For those interested to learn more about this subject, tomorrow's conclusion will include a bibliography.
And so, DKos community, we come to the end of another trail, another armchair tour. See you tomorrow for the finale to this series. I will also be moving to a new locale this week (remaining here in the Burqy-Albuquerque), so if I don't reply to your comments (as I always do), I will do so later this week when my Internet service is restored.
Meanwhile, your thoughtful commentaries are welcomed.
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