Hypsometric Curve and Integral

Hypsometric curve shows the percentage of the Earth’s surface above any elevation. The horizontal axis, labeled “% of Earth’s surface,” gives the percentage while the vertical axis shows elevation above or below sea level.

Hypsometry vs Bathymetry : Hypsometry is The measurement of land elevation (MSL) while Bathymetry is the measurement of underwater elevation.

How to read the graph :

Using the hypsometric curve, determine the minimum elevation of mountains that make up the highest 10% of the Earth’s surface.

Find 10% on the horizontal axis.
Draw a line up from 10% until it reaches the hypsometric curve (the dark red curve).
Now, draw a line across to the vertical axis (at approximately 0.5 km).
So, you find that 10% of the Earth’s surface has an elevation of 0.5 km or higher.

Uses of Hypsometric Curve :

Isostasy – buoyancy of the oceanic crust, elevation changes due to temperature changes in the crust,
Continental and oceanic crust – determining the elevation of oceanic and continental crust, differentiating between oceanic and continental crust
Planetary geology – the examination of other planets to look for different surfaces, the examination of planetary surfaces for evidence of plate tectonics.

Hypsometric Integral :

The hypsometric integral (HI) is a geomorphometric metric that is used to infer temporal stages of geomorphic development. The HI is non-dimensional and is calculated by dividing the difference of the catchments average and minimum elevation by the difference of the maximum and minimum elevation (HI = (Hmean – Hmin)/(Hmax – Hmin)). Values of HI generally range between 0.15 and 0.85, and typically cluster between 0.4 and 0.6. Lowland areas with isolated high-standing surfaces have lower values whereas high values denote landscapes with mainly elevated surfaces which are steeply dissected by valleys.

The types of hypsometric curves (youth, mature and old stages of geomorphic development) as elaborated by Strahler

There are different shapers of hypsometric curves through the comparison of different drainage basins, and classified basins according to their stages of geomorphic evolution as:

Youth stage : (con- vex upward curves, where Hi ≥ 0.60), where the watershed is highly susceptible to erosion and landslide.
Equilibrium or Mature stage : (S-shaped hypsometric curve which concave upward at high elevations and convex downward at low elevations, where 0.30 ≤ Hi ≤ 0.60)
Peneplain (old) or Monadnock stage : (concave upward curve, where Hi ≤ 0.30)

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