# WOW! 2 Miles Thick!

What would the pressure be at the bottom of a 1'x 1'x 2 miles column of ice ?

This is going to be an approximate solution so let's assume ice is a little lighter that fresh water .

Assume the density of ice = 60 lbs/cu.ft.

The pressure at the bottom of the column of water would be:

Height of ice column = 2 x 5280 = 10,560 ft.

The volume of the column of ice = (1)(1)(10,560) = 10,560 cu.ft.

The weight of the column of ice = 10,560 x 60 = 633,600 lbs. (You would not want your foot under there!)

Pressure = force / area = weight of column of ice / area of base of the ice column

= 633,600 / (1)(1) = 633,600 lbs/sq.ft.

The pressure in terms of sq. in. :

Pressure = 633,600 lbs / 144 sq.in per sq.ft. = 4400 lbs / sq. in. or 4400 psi

A concrete test cylinder of normal strength concrete will crush at 3500 psi

and wood has an allowable compression stress of 1800 psi (parallel to grain).

The allowable bearing capacity of soil is approx. 2500 psf (17.4 psi) (varies widely) .

There's no wonder that great lakes where formed by the movement of glaciers during the ice age!