In this series of scans Spider-Man tanks, to quote the omnicient narrator; "half a mountain" falling on him. The Hulk caused the collapse, so I doubt it was hyperbole. Spider-Man literally drops in on this mountain range from a plane earlier, and we're told he's three miles in the air. That seems to also roughly be the height of the mountains.
We'll use the mountain in the background for the calc.
The mountain is three miles or 4828.03 meters and 298 pixels tall.
Its radius is 361 pixels or 5848.72 meters.
Volume of a cone = (pi × r2 × h)/3
Mountain's volume = 172,949,923,273 m^3
Density of continental crust, stone and earth = 2700 kg/m^3
Mountain's mass = 466,964,792,837,100 kilograms
Half of mountain = 233,482,396,418,550 kilograms
Spider-Man is 1.778 meters and 157.86 pixels tall.
The distance between Spider-Man and the falling mountain is 335.97 pixels or 3.784 meters.
Instantaneous velocity = sqrt(2gd)
d = 3.784 meters
g = 9.8 m/s^2
Speed of falling mountain = 8.612 m/s
Kinetic Energy = 8,658,351,976,714,551 joules or 2.069 Megatons of TNT
Low 7-B Small City Level