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Asia As the block consisting of Australia, India, and Southeast Asia slammed into Asia, Europe was being pulled away by North America. The crustal wave, shown here in blue, is actually beneath the continents. The collision with Asia shattered the block and built mountains. The crustal wave split in two. The collision sent Australia careening eastward. As Asia moved north, more mountains grew and Japan was thrown outward, forming a trench. Momentum drove India and Southeast Asia deeper into Asia, causing China to be pushed out. Asia pivoted counterclockwise, driving Europe down and raising the Ural Mountains.
This is the topography of the pivot area.
Southeast
Asia collided with Asia along the Red River fault zone, which "is
the major geological discontinuity that separates South China from
Indochina." As India drove into Asia, China was pushed
to the east, sliding along the Red River fault zone. "It is fair to say that this zone is
to continental strike-slip faults what the Himalayas are to mountain
ranges."
The
formation of the Ural Mountains "involved large-scale (up to
100-150 km) westward overthrusting . . . This gave rise to the
orogenic belt."
South Asia is the most spectacular example in the world of continental collision and mountain building by collision. Yet researchers are still wrestling with what happened there in the context of plate tectonics. "Convergence between the Indian and Eurasian plates is estimated to be at least 1000-1400 km or as much as 2000-3000 km. How this shortening has been accommodated is still not well known."1 One study found that continents riding on the 'plates' of plate tectonics are not very solid. Using a precision radar-satellite method to measure deformation to within a few millimeters, researchers had these comments: "Satellite measurements
of the Tibetan Plateau suggest that when continents go head-to-head
in mountain building, they can behave more like unbaked pizzas."
"The latest evidence for squishy continents comes from
a satellite-borne technique called interferometric synthetic
aperture radar (InSAR)." "The plateau, the researchers
conclude, is yielding and deforming like so much putty." "
'In my view, there's no question,' says [Peter] Molnar [of Colorado
U. - Boulder]. 'Continental tectonics is not plate tectonics.'
" "The upper 100 kilometers of rock 'really looks
like a fluid' in GPS maps of surface motion, says [Roger] Bilham [of Colorado U. - Boulder]. 'It's as if India were colliding
with a water bed.' "2
Researchers
using tomography to look deep below the surface found "that
underthrusting of Indian lithosphere far beneath the Tibetan plateau
is restricted to the western part of the collision zone." Their
"observations argue against significant underthrusting of the
Indian lithospheric mantle beneath the eastern plateau", going
"no further than the Himalayan Block" in the foothills
of southern Tibet.
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