Elaine Meinel Supkis
The death toll from the 7.9 earthquake in China grows greater. Heroic efforts by the Chinese military and others, trying desperately to dig out the unfortunate people trapped in the rubble continues. As usual, regulating the building earthquake-proof structures is a very important government function. The many tragedies we see in earthquakes are due to improper or weak architecture. Modern cities must heed the lessons of other cities' woes! The school that collapsed in China is a classic example: it should have never happened. Also, we look yet again at the Himalayan mountain region and the geology of central China and why this is so unstable. Geologists are still trying to figure out how the earth's different elements intersect and interact there.
A massive search and rescue operation is under way in south-western China after one of the most powerful earthquakes in decades. Troops have arrived in Wenchuan county at the epicentre, which was largely cut off by the quake - but heavy rain is hampering rescue operations.
Elsewhere in Sichuan province, frantic efforts are being made to reach thousands of people under the rubble.
The death toll is now more than 12,000, officials say, and looks set to rise.
It is quite moving to see the frantic efforts of the military as they burrow deeper and deeper into the school to dig out the children. Some of the children are still alive. The soldiers are bringing in IV fluid to attach to survivors who are in shock as well as dangerously dehydrated from the cement dust in the ruins. These efforts are in strong contrast to the horrors of the poor, suffering people of Burma. There, the madcap military dictator refuses to give even slight aid. Maliciously leaving the people to fend for themselves, already over 30,000 have died. By the way, all of this is a reminder as to why we have a central government and why it has to exist to protect the people from earthquakes, volcanos, tsunamis, etc. Our own government has sent much of our own military to Iraq rather than have them here to protect us. When the inevitable earthquake wrecks a good part of California, there will be no soldiers to come pouring in within the first 6 hours to dig out survivors or bring aid.
This is a warning to all Americans to cease sleepwalking in the Iraq war! If we continue this way, we will pay in precious lives at home. If our rulers want wars, they can raise troops some other way. Not send all our National Guard far away.
I have written extensively in the past about the Tibet/China clash of continental land masses. India, which is part of the Austro-Indian plate, has moved northwards very rapidly and slammed into Eurasia, causing the greatest mountain building on earth. This week's massive earthquake is related to this business. Surrounding this tremendous mountain building is some of the queerest geology on earth. When we look at this part of the planet using different tools, we see clearly, something is not right. The thinnest crust is right next door to the thickest crust on earth. And the dynamics of the lithosphere is very strange here, probably due to the rapid movement of the India half of the large plate which has not one but two continental masses. Here is an earlier story I wrote about all this:
One thing about wanting pet theories to work is to look at one or another aspect. Then the puzzle seems to 'fit'. But always, when arranging a theory, one has to look at all possible similar situations and see if they match in any way. The fact of this matter is, definitely something is at work with the Tibetan plateau, the fact that the center of the Tibetan highlands is an awful lot like so many other centers of massive mountainbuilding/continental collisions means there is something rather common about all these situations. Namely, they are all operating on the same principles.
I used a box of Jiffy mix yellow cake and baked it at 400 degrees. Then I let it cool rapidly and it collapsed very neatly. A fun experiment if you don't mind a cake raw in the center and over-baked on the edges.
In this case, I would suggest that when plates, both oceanic and continental, collide and one begins to climb over the other, it is like baking a cake, literally, since this friction and compression 'cooks' everything, the whole beings to rise until a critical point is reached and then the center collapses, leaving a classic ring of mountains around a depressed center.
Perhaps the mantle, after a lot of landmass piles up on top of it and it is compressed more and more, a section in the center breaks off and begins to sink. As this slips lower, the mountains around the developing sinkhole rise, sort of like if you press down on a pillow, the edges rise.
By Paul Rodgers
Published: 18 February 2007
The discovery of the missing mantle - the cold, heavy rock beneath the crust - was revealed last week by Professor Wang-Ping Chen at the University of Illinois, whose team used more than 200 super-sensitive seismometers strung across the Himalayas, from India deep into Tibet.
"While attached, this immense piece of mantle under Tibet acted as an anchor, holding the land above in place," said Professor Chen, whose results are to be published in the Journal of Geophysical Research. "Then, about 15 million years ago, the chain broke and the land rose."
By pushing the Himalayas to their current altitude, more than 8,000m above sea level, and raising the Tibetan plateau to 5,000m, the detachment of the block was responsible for both the monsoon rains that make south Asia so fertile and the Gobi desert in central Asia. Warm winds blowing from the Pacific Ocean cool as they rise over the mountains, releasing the moisture they contain as torrential rains, leaving almost no water to fall on the arid interior of the continent.
Nearly all of the great quakes are at the 10 kilometer level. As we see here with this latest example:
Another interesting aspect of this latest quake in China is how far it was felt: 1,000 miles! The entire eastern half of the nation felt it. A year ago, I found some great gravity field maps of the earth while doing a story about meteorite strikes on the moon.
The gravity field right below India is by far and away, the lightest on earth. But the densest is where the rest of the Australian-India plate is being subducted under the Asian plate: the most geologically active area on earth, the Sumatran chain. The densest place on earth is not the Himalayan mountains nor the Rocky mountains. It is actually the front edge of this very fast moving plate. This same plate is also moving much faster than all the other plates on earth at this time. The speed is many multiples faster than the rest of the continents. Geologists still don't know why this is. But obviously, there is a great disturbance in the planetary lithosphere connected to this particular plate! The other place with a high gravity value is, oddly enough, the north Atlantic Ocean.
I drew in some lines showing the outer edges of the Australian plate which clearly shows how it is wrapping around the Asian plate. Both India and Australia ride along their plate while the middle section between them is being stretched and warped as it folds around Asia. India, on the other hand, is crashing into Asia and shoving it rapidly upwards. Is this plate being stretched to a great degree by all this? Is this why the weakest gravity spot is right next door to the Sumatran subduction zone?
All of this is very connected with the geology of China. China is being squeezed like in a vise by the Australian-Indian plate. For the last 2 months, the Sumatran subduction zone which has been tremendously active since the Great Boxing Day Quake, one of the biggest quakes in 100 years. Japan just had a serious quake just offshore last week. Now, this latest big quake in China. And the US West coast is still having quakes along the Juan de Fucas and the San Andreas system, far more than in the last 5 years. Perhaps the energy released from the Great Boxing Day Quake has worked like a spring to pop the Australian half of the plate northwards yet again, shoving the Pacific Plate ever harder against both the Asian subduction zone off of Japan as well as the North American Plate?
In Asia, behind the leading edge of the fast moving Australian-Indian Plate, we see some interesting features. Nearly always, when plates collide like this, we get volcanos and huge uplift mountains. Several things here: the leading edge of India is not producing volcanos. It is causing only uplifts. Nor are there any volcanos in Burma and Thailand, for example. Only further to the south, in Sumatra, are there volcanos and these are some of the nastiest ones on earth. I also highlighted two interesting features in China, both of which are important in today's story about the earthquakes: the Xinjiang depression and the Chengdu depression. These are behind the Himalayan mountains. Actually, there are other, similar depressions. All over the planet, active geological areas where there is rapid mountain building, we see these odd depressions. All active mountain regions have 'long valleys' associated with them that often lie between costal mountains next to subduction zones and more distant mountains due to uplift.
Qing-Ren Meng and Guo-Wei Zhang
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
The geologic framework of the Qinling orogen was built up through interplay of three blocks, the North China block (including the North Qinling), the South Qinling, and the South China block, separated by the Shangdan and Mianlue sutures. The Shangdan suture resulted from Middle Paleozoic collision of the North China block and the South Qinling. The Mianlue suture resulted from Late Triassic collision of the South Qinling and the South China block. Present upper crust of the Qinling is structured dominantly by thrust–fold systems. The North Qinling displays thick-skinned deformation with crystalline basement involved, whilst the South Qinling is characterized by thin-skinned thrusts and folds detached above the Lower Sinian. Two types of Precambrian basement, crystalline and transitional, are defined according to lithology and metamorphic grade and different in age. Stratigraphic and sedimentary architecture is characterized by distinct zonation.
The Qinling orogen experienced a prolonged continental divergence and convergence between blocks. During the period from Late Neoproterozoic to Early Paleozoic times, the South Qinling was the northern margin of the South China block, and the North Qinling was the southern margin of the North China block, separated by a Proto-Tethyan Qinling Ocean. The North Qinling evolved into an active margin when the Proto-Tethyan Qinling Ocean subducted northward during Ordovician time. Collision of the South and North Qinling took place in Middle Paleozoic along the Shangdan suture. Synchronous with the collision, rifting occurred at the southern rim of the South Qinling and was followed by the opening of the Paleo-Tethyan Qinling Ocean during the Late Paleozoic, resulting in the splitting of the South China block from the South Qinling. Collision of the South Qinling and the South China block came about in the Late Triassic along the Mianlue suture. The Late Triassic collisional orogeny caused extensive fold-and-thrust deformation and granitoid intrusions throughout the Qinling, and led to final amalgamation of the North and South China blocks.
In other words, China is actually two major continental masses that have been alternately squeezed and then depressions widened, most likely due to the sudden collapse of the lithosphere. The resulting ocean was then eliminated due to the nutcracker effect of the break up of the Antarctic-Australian-Indian plate, most likely due to the Permian meteorite strike that may have eliminated most life forms in the greatest extinction on earth. This is probably why, outside of the depressions of Xinjiang, Chengdu and Mongolia, China has virtually no flat plains like India, Russia, the US, central Africa, Brazil, etc.
Several orogenic belts transecting eastern China are the sites of former convergent plate margins, although there have been varying views on the collisional framework of individual continental blocks, styles of convergence at these zones, and the timing of respective collisions. A tectonic study of eastern China, Mongolia and the southern Soviet Far East indicates the collision of the South China Block with a combined North China-Northeast China Fold Zone Block in the Late Triassic-Early Jurassic, their collective suturing to Eurasia in the Late Jurassic-Early Cretaceous, followed by the Sikhote Alin-Japan Block in the Mid to Late Cretaceous.
The evidence is as follows: (1) A linear belt of Late Triassic-Early Cretaceous granites and granodiorites trends east from the Qinlingshan through the Dabieshan to the Huaiyang massif. Ophiolites, flysch, subduction zone melange, a paired metamorphic belt indicating north dipping subduction and marine strata of Carboniferous to Late Triassic age from the Qinlingshan define the suture between the North and South China Blocks,
(2) A sinuous belt of ultramafics, blueschists, silicic to intermediate magmatism and west and north vergent folds and thrusts trend from the west margin of the Ordos Basin through central Inner Mongolia and along the east Great Khingan Range to the Amur River. Coupled with a Mid Jurassic-Early Creataceous unconformity a suturing of eastern Chinese blocks to Eurasia along this zone is suggested,
(3) A fold and thrust belt with ultramafics, flysch, blueschists and subduction zone melange along the Ussuri River in northeast China indicates the suturing of the Sikhote Alin-Japan Block to Eurasia along a west dipping subduction zone in the Mid to Late Cretaceous. Similarly, a tectonic study of southern China and Southeast Asia has revealed a complex regional mosaic of suture-bounded terrains which nucleated about the eastern, western and southern margins of the Yangtze Craton during the Late Triassic and Early Jurassic. The evidence is as follows:
(4) A north–south trending belt of ophiolites, blueschists, calc-alkaline volcanics and subduction zone melange, including granites, granodiorites arid strongly deformed marine strata all of Late Triassic age exposed in the Longmenshan of Sichuan merge with the Kekexilishan ophiolite zone Into the Ailaoshan-Tengtiaohe ophiolite and blueschist belt in central Yunnan along which the Songban-Ganzi Complex and the Shan-Thai-Malaya Block join the Craton, and
(5) A southeastern prolongation of the Ailaoshan-Tengtiaohe belt bifurcates into the southeast trending Konvoi zone of northern Vietnam and the north–south trending Pak Lay-Luang Prabang zone of Laos and eastern Thailand. Zones of ophiolite, calc-alkaline volcanics and strong Late Triassic deformation, they separate the Indosinia and Shan-Thai-Malaya Blocks from the Craton respectively. These findings differ significantly from previous interpretations of a Late Paleozoic consolidation of South–Eastern Asia as well as disputing the existence of a true Pangea.
The dispute about the inner workings of this region continue and shall continue as geologists unearth greater details of this strange region. I still think the biggest mystery is why the Australian-Indian Plate is moving so fast in the first place. India definitely has been greatly slowed down ever since plowing into Asia but Australia is still moving at a tremendously fast geological rate and by far, the most earthquakes on earth are along the leading edge of Australia. The fact that Australia itself is so geologically silent while creating the greatest havoc on earth is also a big puzzle. Eventually, all of Southeast Asia will be folded into China and perhaps Japan will be crushed between Australia and Russia a few million years from now.
The inner reaches of the Earth remain shrouded in mystery. Even the surface of Mars has been explored more extensively. Because deep drilling comes to a halt after a maximum of 12 kilometers, the remaining 6,300 kilometers to the center of the Earth remain inaccessible.
“Old, cold plates are pushed down into the Earth’s mantle on the continental edges,” he explains. “At this point they collect large amounts of iron. You can imagine it as something similar to water condensation.” Weighted down by the iron, the plates sink farther and farther into the hot, molten rock until they reach the inner sanctum of the Earth’s mantle. There, at a depth of 2,900 kilometers, they finally halt their decent and settle into “plate graveyards.” This is presumably the outer edge of the earth’s heavy core, where the temperature is 4,000 degrees Celsius (7,200 degrees Fahrenheit).
Brimming with enthusiasm, Maruyama continues: “But the capsized continents don’t simply rest in their plate graveyards forever.” Rather, they are about to experience a sudden resurrection. Heat and pressure in the depths trigger chemical processes, causing the plates to deposit their load of heavy elements. Once liberated of this burden, they become lighter than their surroundings, causing them to rise like corks in water. The result: Above the old plate graves, on the floor of the Earth’s molten mantle, a mushroom-shaped upwelling of abnormally hot magma called a mantle plume makes its way toward the surface.
Eventually, the rising flow of molten rock reaches the crystallized crust and cuts through it like a welding torch. Volcanoes form, such as those on the Big Island of Hawaii. Maruyama says the red hot lava that erupts on the volcanic island comes directly from an old plate cemetery 2,900 kilometers below the surface, where the remains of an ancient continent that broke up some 750 million years ago simmer to the surface. His theory postulates the amazing comeback story of this ancient rock from the deep.
All this surface chaos is causing parts of the lithosphere to detach and collapse. The latest major earthquake is in such a battle ground: on the edge of a nearly circular spot where there is surrounding mountains and a depression.
The movement of India is most astonishing: unlike most other plates, when the India subcontinent calved off of the Antarctic landmass, it took off like a bullet and shot north, hitting Asia which is moving eastwards in a long, slow arc, slamming into the belly of that great landmass with such forward force, it has raised the tallest mountains on earth which are still rising for this sector hasn't exhausted its momentum yet.
What lurked under the joining of India, Africa and Antarctica? That center point where everything broke apart? Why is the deepest low gravity point associated with the Indian Ocean Plate and India itself INCLUDING TIBET?
The question is, why are the two largest land masses on the northern hemisphere moving in a turning motion, towards one spot in the Pacific? We know they are being pushed but why in that particular direction? There is nothing at the North Pole that could be pushing them, is there? Antarctica is nearly totally stationary. Perhaps this is due to the heavy load of ice sitting on top. The earth isn't round and we have a moon that has enough gravitational pull to yank the huge oceans into high and low tides that are quite obvious on the ground.
We also have a widening Atlantic Ocean that is smaller than the Pacific. The weight of the oceans, the thinness of the ocean floors, the lithosphere, all these things affect the movement of the plates.
Here is a map of the earth I drew last year showing the general movement of the earth's plates. Note how the pressure directions for Asia are all towards the Pacific. And the leading edge of India is not due north but actually aimed straight at the region where yesterday's earthquake occurred.
This map I drew shows how all the plates except for South America are being dragged relentlessly towards one spot in the Pacific Ocean just offshore of Japan, around the Micronesian Islands. Maybe this is where the New Pangea will arise?
Perhaps the base of Australia (and India) were detached from the lithosphere allowing them to flow with minimal friction? One can only guess. What we do know is, the leading edge of Australia is causing mountain building via volcanoes. But the buckling of the continent's leading edge is minor compared to the leading edge of North America that is violently buckling under the stress of trying to crash over the Pacific Plate, indeed, it is probably shoving that plate westards at a good clip, considering. Except this doesn't explain much of anything!
Why is the Pacific Plate moving so swiftly into Asia? It hits Asia and slides under with great violence. We know that Eurasia is moving towards the Pacific thanks to the Atlantic rifting. But why is it cartwheeling to this one point in the ocean that happens to be the same spot Australia is determined to head into? If I were looking at this as a dynamic system on a flat surface, I would suspect there is some magnetic force at work, if this were concave, I would suspec that is the lowest point.
But this is a globe and there is no singular reason for all the northern landmasses to move towards that spot. Heh. Maybe I should call it 'The Great Attractor' in honor of that mega-complex of galaxies that our own is heading towards at break neck speed!
And this week's news reminds us of the curious business concerning the 10 kilometer level. Why is this a very favorite level for mega-earthquakes?
One of the things that always intrigues me is the number of earthquakes at the 10km level. Many 8 to 9 mag earthquakes like the terrible Boxing Day Tsunami event, are at that depth. Click on the chart here to enlarge it. This is from 3/3/2007, a normal day with a long list of earthquakes. Nearly half of them are at the 10 km depth.
Up until recently, we were taught that the lithosphere was the same all over except where it was being subducted under a continent, for example. Also, theories about tectonic plate movements suggested that the continents were basically unchanging except at the outer edges where they would bump into each other or join together like India crashing into Asia. But as scientists probe this planet's innermost structures, a totally different picture is now emerging, one that is very disturbing.
The continents are actually quite prone to falling apart because the base upon which they rest can suddenly collapse.
The discovery that a segment of the ocean floor, not just the lithosphere but the whole thing, fell away suddenly into the depths of the mantle, is an eye-opener indeed. This event happened where the earth's plates are moving apart but I suspect this is the wrong imagery. Perhaps the better idea is to think of the split that runs the entire planet from the Artic to the Antarctic plate is a serious crack in the earth.
These are two charts I drew up last year, while wondering about how the lithosphere operates.
Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.
So, on top of literally everything, part of Tibet is actually being rotated in place while everything around this section is moving in one direction, northwards, due to India? If India was just a single continent mashing itself into Asia, we wouldn't see all these peculiar geological situations in China, would we? I would surmise that all these peculiar conditions are due to the entire Australian-Indian Plate riding up over Asia as India is doing while the other half is being subducted under Asia here the Australian-India Plate is very weak and underwater? So this is stretching both the Australian-Indian Plate as well as twisting and turning the Asian Plate where it is the weakest...namely, in the regions where east and west China were mashed together by this same Australian-Indian Plate movements?