Do elevation and depth change pressure?

Answer 1

Pressure is directly proportional to depth. The equation used is for hydrostatic pressure:

P = Po + dh

Where P = pressure, Po = initial pressure at surface, d = density of the fluid, and h = height to the free surface (or depth). In diving, Po is usually the atmospheric pressure. This is the only thing that elevation affects, as sea level air pressure is higher than the air pressure at higher elevations.

The density of sea water is generally accepted as 64 lbs/cu ft. There is variation, but usually not enough to be meaningful, unless you are diving in a very high salinity location, like the Dead Sea, in which the salt content is so high that the density is considerably higher.

For most purposes, atmospheric pressure at sea level is accepted to be 14.7 lbs/sq in (14.7 psi), or 2116.8 lbs/sq ft (2116.8 psf). Diving in sea water then, the equation becomes:

P = 2116.8 lbs/sq ft + 64 lbs/cu ft x h.

Then, at the surface, h = 0, and P = 2116.8 psf = 14.7 psi. At h = 10 ft, P = 2116.8 + 64 x 10 = 2756.8 psf = 19.1 psi. At h = 33 ft, P = 4228.8 psf = 29.4 psi. At h = 100 ft, P = 8516.8 PS = 59.1 psi. And so on. The general rule-of-thumb for sport/recreational diving is that the pressure increases by 14.7 psi (1 atmosphere) for every 33 ft of depth. So that at 100 ft, the pressure is 58.8 psi (4 atmospheres). (Remember that you start at the surface at 1 atmosphere.)

Answer 2

Yes, pressure varries with depth or elevation.

Answer 3

Yes. Either way. If you ascend or descend through the atmosphere,

the atmospheric pressure changes in the opposite direction.

Answer 4

Yes, pressure varies with depth or elevation. You must acount for this while diving in oceans and also in flying small aircraft. It's very important to set pressure on your altimeter.