The model below was generated using a technique called Structure-from-Motion (SfM) on Khumbu Glacier in Nepal. SfM involves taking photographs of the area of interest from different positions using a standard digital camera (see the animaton below). These images are then run through specialist software which matches textures that are common between several images. The software is then able to reconstruct a 3D point cloud of each matched point, which can be converted into a terrain surface. The original photos are mapped onto the surface to create a realistic colour scheme. Repeat surveys of this kind can be used to estimate how much the terrain has changed between surveys. In the model below, the ice cliffs would have retreated due to melt if they were subsequently resurveyed, which would be captured by the software with high precision.
Click on the numbers to reveal the annotated features. You can navigate the model by holding the middle button of your mouse.
Ice cliffs on debris-covered glaciers range from several to tens of metres high. Some have a dark surface covered by debris whereas others may be bare ice. Debris around the cliffs is generally thick enough to insulate the ice beneath, slowing the melt rate. This means that the highest melt rates are found at ice cliffs, making them of interest to scientists studying the response of glaciers to climate change. Some cliffs have surface water ponding at their base called supraglacial ponds. These ponds absorb solar radiation and can increase the melt rate of the cliff by undercutting it.
This animation shows the process of taking photos of an ice cliff from many different locations (each shown by a blue rectangle). These photos were used to make the 3D model shown in the interactive animation above, and in the fly through animation below.