Continents sliding away from a central explosion does appear to produce the shapes and features of most of Earth's crust in a simple, straightforward way. Once it is clear that an event happened, the discussion about whether it is possible or not is over, and the question turns to "how?". How did the landmasses slide?
For perspective, note that while several thousand miles is a long way for us humans, most of the continents slid only 12-16% of the distance around the world at the equator. Australia went farthest: 32% of Earth's circumference.
People are too small to experiment with huge continents, so any explanation must be speculation. However, there is an interesting possibility.
An odd phenomenon has been identified on Earth and other members of the solar system. Large landslides don't just fall to the base of the mountain the way small ones do; they often go great distances, some up to 30 times the distance they fell.
Dr. H. J. Melosh has proposed that long-runnout landslides, earthquake slip, and the making of complex craters reveal a characteristic of the crust. Put simply, it temporarily acts like a fluid when enough stress is applied. In 1979 he gave it the name "acoustic fluidization."
weakening mechanism most widely adopted in numerical impact simulations
is acoustic fluidization." "According to this idea,
pressure fluctuations in the fragmented rock mass behind the impact-generated
shock wave periodically allow sliding to occur at lower shear stresses
than would occur under the normal overburden pressure. The
space- and time-averaged result of this process provides a temporary
'fluidization' of this material for as long as strong pressure fluctuations
persist. Acoustic fluidization is the most widely adopted
explanation because numerical models that employ it as a weakening
mechanism have successfully reproduced many specific craters and
the general crater sizemorphology progression." "In
the Block-Model of acoustic fluidization, some fraction of strong,
transient pressure fluctuations (seismic energy) initiated by the
passage of the impact-generated shock wave is responsible for temporarily
counteracting overburden pressure, thereby reducing the frictional
resistance of the blocks within granular breccia."
"Structural observations from the peak-ring target rocks of
Chicxulub [crater] are generally consistent with acoustic fluidization as the dominant
weakening mechanism. Drilling of the
approximately 200-km diameter Chicxulub impact structure in Mexico has produced
a record of brittle and viscous deformation within its peak-ring rocks. The observations point to quasi-continuous
rock flow and hence acoustic fluidization as the dominant physical process
controlling initial cratering."
known on a small scale as a Bingham Fluid, Melosh suggests that
fluidization at the base of large landslides reduces friction
to near zero.
In a paper computer-modelling long-runnout landslides, Melosh and two others wrote: "For rock masses with volumes exceeding 109 m3, these landslides regularly run out more than 10 times longer than the height they fall from."
"Many mechanisms have been proposed to explain this apparent reduction of friction: riding atop a cushion of trapped air; lubrication by water; a basal frictional melt layer; frictionally warmed ice; frictional velocity-weakening; a basal layer of colliding grains (dispersive grain flow); and acoustic fluidization."
"Our results are very similar to the predictions of the acoustic fluidization hypothesis, where the flow is effectively fluidized by local variations in the contact forces between the grains. Acoustic fluidization is similar to the pore pressure fluctuations observed in debris flows, but without an interstitial fluid. The acoustic fluidization wavelength is determined by the size of the rock fragments in the slide."
"Friction is reduced even during the earliest stages of the slide. Although the slides have similar maximum velocities, larger slides initially accelerate faster than the smaller slides, implying a smaller effective coefficient of friction even at the onset of sliding."
"We note that channelized slides do not exhibit
systematically longer runout distances than unconfined slides, suggesting that
spreading perpendicular to the main slide path is not of fundamental importance
to the runout."
There is an important
feature of long-runnout landslides that have stopped moving:
"Ridges formed at the front and rear of the debris support
the hypothesis that the leading edges of the slide initially ground
to a halt and the rest of the material piled up behind it."
Corresponding to the falling side of a mountain that powers a landslide, the explosive power released by the giant meteorite on impact would have set the landmasses in motion with the force of billions of megatons of TNT, generating acoustic energy. The continental crust's mass would confine the acoustic energy to the base of the crust.
Shi Jian-chun, Ma Yue-hua, Bao Gang. 2009. The Formation Model of Multi-ring Basins Based on the Theory of Impact Tsunami. Chinese Astronomy and Astrophysics, Vol. 33, pp. 287-292.
"The acoustic wave field may evolve by progressive
lengthening of the dominant vibrational wavelength during cratering as
higher-frequency vibrations dissipate sooner." So the wavelength would increase greatly as it moved out
from the crater.
These are snapshots from models of wave field propagation in the crust. Note the disturbance in the entire region behind the wave front:
Left - Frankel, Arthur, Robert W. Clayton. May 10 1986. Finite Difference Simulations of Seismic Scattering: Implications for the Propagation of Short-Period Seismic Waves in the Crust and Models of Crustal Heterogeneity. Journal of Geophysical Research, Vol. 91, No. B6, pp. 6465-6489.
Right - Martini, Francesca, Christopher J. Bean, Sean Dolan, David Marsan. 2001. Seismic image quality beneath strongly scattering structures and implications for lower crustal imaging: numerical simulations. Geophysical Journal International, Vol. 145, pp. 423-435.
The Shock Dynamics scenario
With all the action at the surface, it follows that features in the oceanic crust are fairly shallow. They include these:
Mid-ocean ridges and transform faults, where surface melting results from the removal of the weight of continental crust (pressure relief melting).
"A tray of melted paraffin was cooled by a variable-speed fan until a film of solidified wax formed between one end of the pan and a movable stick. The stick... was drawn at a uniform rate through the wax by a variable-speed a/c motor". The pattern of spreading ridge segments with transform faults between them was produced. "The upwelling of material is a result only of hydrostatic forces in the fluid caused by the separation of the plates." "The ridge crest has moved at one-half the spreading velocity." "Typical values for the velocity of the stick are a few millimeters per second." "The thickness of the solidified wax is typically less then 0.5 mm near the ridge crest and may increase up to a few millimeters near the plate boundaries." If the separation speed was too slow, the ridge crest solidified and a new ridge opened up in the same segment.
Oldenburg, Douglas W., James N. Brune. 20 October 1972. Ridge Transform Fault Spreading Pattern in Freezing Wax. Science, Vol. 178, No. 4058, pp. 301-304.
Another experiment with spreading wax plates found that fast rates of separation produced longer transform faults and larger distances between ridge segments.
Subduction zones (green line) along the leading edges of landmasses result from the rapid application of the weight of continental crust. Towards the end of a continent's run, friction compresses the leading edge, raising mountains.
A crustal wave (red line) from the low angle impact was launched in the direction of travel of the meteorite, and "froze" in the end to form an inclined subduction zone.
Below is a detailed computer-generated 3D map of the Mariana Trench terrain at the bow. The colors designate elevation. Notice the wavy light-blue seafloor ridges that look like clouds between the arcs. They tell us these features were formed by fluid turbulence.