Which variable does the y-axis represent?

The “dependent” variable goes on the y-axis (the left side, vertical one)

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.

Answer steam fog;