Distances, maps, coordinates and the planet
Great-circle distance between two lat/long points.
Ratio of map distance to real-world distance.
Steepness of terrain as a percentage.
Approximate drop of the horizon over distance d.
Atmospheric pressure as a function of altitude.
Approximate ground distance per degree of latitude.
Earthquake magnitude from seismograph amplitude.
Number of people per unit area.
Each 15 degrees of longitude equals one hour.
Energy released by a quake of Richter magnitude M.
Modern magnitude from the seismic moment of a quake.
Speed of an elastic wave through rock.
Pressure from the weight of overlying rock.
Temperature rise with depth into the Earth.
Speed of a shallow-water wave across the ocean.
Age of a rock from parent and daughter isotopes.
Fundamental electromagnetic resonance of the Earth.
Depth of a mountain's crustal root floating in the mantle.
Rate of groundwater flow through porous rock.