"Our compilation of mountains throughout the world shows that a major phase of uplift occurred in the Pliocene-Pleistocene."  "Uplift occurred over a relatively short and distinct time.  Some earth process switched on and created mountains after a period with little or no significant uplift.  This is a deviation from uniformitarianism."
The Origin of Mountains. Cliff Ollier, Colin Pain. 2000. Routledge, London. p. 303.

"Virtually all major mountain ranges in the world are a consequence of crustal shortening."
Some Simple Physical Aspects of the Support, Structure, and Evolution of Mountain Belts. Peter Molnar, H. Lyon-Caen.  Special Paper 218, Geological Society of America, 1988, pp. 179-207.

The presence of mountains on the front and back sides of continents (along their line of travel), the relatively short distances travelled, and the brief burst of mountain building point to a sudden impulse rather than a steady, constant force moving the continents. Important driving forces of plate tectonics theory are too weak to raise mountains.

In Shock Dynamics, the shock wave from the giant meteorite impact provided the impulse that initiated continental motion.  Some continents began moving after being hit by a continent already set in motion by the impact.  Assuming the acoustic fluidization mechanism, and assuming that mountains are built through lateral compression, the minor mountains (such as the Appalachian Mountains) raised by the impulse against a continent's back side indicate a comparatively slow acceleration.  The major mountains (such as the Rocky Mountains) raised on the front, or leading, side indicate a sudden deceleration, like a multi-car pile-up on a highway.  This braking effect all along the leading edge suggests that acoustic energy was lost most rapidly there, probably through thinning the overlying mass confining the acoustic energy.  Most other mountains were laterally compressed by means of collision with other continents or by torque.

North and South America stopped suddenly because their western sides grabbed the lithosphere below them.  These huge landmasses transferred their momentum to the lithosphere, Earth's outer shell.

So with a jolt, Earth's outer shell, the lithosphere, suddenly slowed its eastward rotation relative to the shell below it, the upper mantle.  We can see this displacement by comparing two scars in the Earth from the giant impact; one shallow, one deep.

In the Shock Dynamics interpretation, they were both made by the same meteorite impact, but the depression in the upper mantle (above right) rotated past the focus of inelastic lithosphere (above left).

Differential rotation continued thereafter and still does, but at a creeping pace of 5 to 13 cm per year.
Doglioni, Carlo, Eugenio Carminati, Marco Cuffaro, Davide Scrocca. 2007. Subduction kinematics and dynamic constraints. Earth-Science Reviews, Vol. 83, pp. 125-175.

In the differential rotation model, the lithosphere and outer core show a net westward drift, while the mantle and inner core move eastwards.
Riguzzi, Federica, Giuliano Panza, Peter Varga, Carlo Doglioni. 2010. Can Earth's rotation and tidal despinning drive plate tectonics? Tectonophysics, Vol. 484, pp. 60-73.
Smith, Alan D., Charles Lewis. 1999. Differential rotation of lithosphere and mantle and the driving forces of plate tectonics. Geodynamics, Vol. 28, pp. 97-116. 

Both features are unique on the Earth, as you can see from the global maps below.

The Earth flexes as the Moon revolves around it.  The place where it is the least flexible is shown in dark blue above.  This solid Earth (body) tide projection was "generated from the actual history of the tidal forcing".  It is a measure of elasticity.
Latychev, Konstantin, Jerry X. Mitrovica, Miaki Ishii, Ngai-Ham Chan, James L. Davis. 2009. Body tides on a 3-D elastic earth: Toward a tidal tomography.  Earth and Planetary Science Letters, Vol. 277, No. 1-2, pp. 86-90. 

"The broad gravity low in the equatorial Indian Ocean south of Sri Lanka is the largest and most striking feature in the gravitational field of the Earth."  It is considered to be a "depression in the upper mantle."
Ihnen, S.M., J.H. Whitcomb. June 1983. The Indian Ocean gravity low: evidence for an isostatically uncompensated depression in the upper mantle. Geophysical Research Letters, Vol. 10, No. 6, pp. 421-423.