Hypsometry

Lore & Background

Hypsometry involves measuring the elevation and depth of Earth's surface features relative to mean sea level. Elevations can be positive or negative, and the distribution is theorized to be bimodal due to the density difference between lighter continental crust and denser oceanic crust. On other planets in this solar system, elevations are typically unimodal, owing to the lack of plate tectonics on those bodies.

A hypsometric curve is a histogram or cumulative distribution function of elevations in a geographical area. Differences in hypsometric curves between landscapes arise because the geomorphic processes that shape the landscape may be different. When drawn as a 2-dimensional histogram, the curve displays elevation on the vertical axis and area above the corresponding elevation on the horizontal axis. The curve can also be shown in non-dimensional or standardized form by scaling elevation and area by maximum values.

In the original paper on this topic, Arthur Strahler proposed a curve containing three parameters to fit different hypsometric relations. Subsequent research using two-dimensional landscape evolution models has called the general applicability of this fit into question, as well as the capability of the hypsometric curve to deal with scale-dependent effects. A modified curve with one additional parameter has been proposed to improve the fit.

Reader's Guide

Hypsometry provides a fundamental framework for understanding Earth's surface topography and its relationship to crustal density and plate tectonics. The hypsometric curve, a key tool derived from hypsometry, allows hydrologists and geomorphologists to assess the similarity of watersheds by comparing the non-dimensional form of the curve.

In limnology, hypsometric curves are commonly used to represent the relationship between lake surface area and depth, enabling calculation of total lake volume and prediction of characteristics such as productivity, dilution of incoming chemicals, and potential for water mixing. The original three-parameter curve proposed by Arthur Strahler has been questioned by later research using two-dimensional landscape evolution models, which noted issues with general applicability and scale-dependent effects, leading to a modified curve with an additional parameter. Hypsometry also connects to practical instruments like the hypsometer, which estimates elevation by boiling water, as water boils at different temperatures depending on air pressure and altitude.