Surface Roughness Analysis as Relative Dating Technique
Author:
Bayasaa Erdene-Ochir ’24
Co-Authors:
Faculty Mentor(s):
Batbaatar Jigjidsuren, Geology & Environmental Geosciences
Ellen Chamberlin, Geology & Environmental Geosciences
Funding Source:
McKenna Summer Environmental Internship
Abstract
When moraines degrade, two distinct changes in their morphology occur: 1) weathering
of boulders on the moraine surface leads to fewer and smaller boulders over time; 2)
initially sharp crests of the moraine become gentle over time as erosion transports
material downhill. These two attributes of moraines, surface roughness and the
sharpness of the crest, are important parameters to characterize the evolution of
glaciated landscapes but they have not been quantified. We established two metrics to
quantify these attributes of moraine morphology using high-resolution elevation data
and compared them against publicly available cosmogenic ages. The surface
roughness of the moraines is proportional to the number and size of the boulders, and
we quantified it by calculating the standard deviation of slope determined from 1-m
LiDAR data. For example, each boulder on the moraine surface produces local slope,
and a large number of boulders on a young moraine should lead to a high variability of
slopes, measured in degrees. Second, we quantified the sharpness of moraine crests
by measuring the maximum curvature along crest-perpendicular transects. Young
moraines tend to have sharp crests resulting in high values of the maximum curvature,
compared to gentle crests of old moraines with low curvature values. We analyzed only
the surfaces of well-dated lateral moraines with five or more cosmogenic ages per
moraine. Preliminary results show a weak negative temporal correlation in the surface
roughness and the sharpness of the moraine crests. However, the correlation is more
apparent at 100,000-yr scale than at 10,000-yr scale, probably because most of the
moraines date to ~16–22 ka. The correlation between these morphologic metrics and
age can be improved by analyzing older moraines from a variety of climate conditions.
This new relative dating technique can be used for mapping glacial landscapes in other
planets, such as Mars.