Consider the Anthill
Glacier dirt mound, a.k.a. anthill, near surface glacial stream. Photo by Steve Jurvetson
April 28, 2023
Allison Sayer - CRR Staff
Ryan Strickland is a PhD student at the University of Arkansas working on building models of glacial features. His goal is to help predict glacial outwash floods. His focus is on determining whether and how observable small features, or microtopography, on glacial surfaces influence how meltwater reaches streams.
Last year I spoke with Strickland about his fieldwork on the Kuskulana Glacier, located near Strelna. I caught up with Strickland again this year to see how analyzing his research was going.
With many thousands of images to analyze, he still has a lot of data to sort through. However, one feature caught his immediate attention. “Looking at the Kuskulana data,” he said, “I became infatuated with the dirt mounds. They seemed like a concrete test case to check my model with: a simple scenario with a simple structure - plus, they’re cool.”
The dirt mounds are known to local glacier aficionados as “anthills.” Insulation from insolation creates an anthill. In other words, if there’s some schmutz on the ice, the sun will melt it more slowly than the exposed ice around it.
“I became infatuated with the dirt mounds. They seemed like a concrete test case to check my model with: a simple scenario with a simple structure - plus, they’re cool. ”
Eventually, a cone will form and some of the larger rocks will roll off of the cone. The cones look symmetrical from the outside, but inside there is a thicker layer of pebbles and dirt on the south side as a result of longer and stronger sun exposure on that side.
Anthills had not been examined in computer modeling as far as Strickland knew. If he created the right parameters, would the simulation indeed create an anthill?
Sure enough, in the simulation he created, a conical shape began to emerge from beneath the debris. After reaching a maximum height, it degraded. This success gave him some confidence that the models he is building could successfully predict other ice, debris and water behavior.
Schematic showing the theoretical formation of a dirt mound from an old moulin. Image courtesy of Ryan Strickland
Scientists studying other physical phenomena may benefit from the humble anthills that populate lonely stretches of ice. Strickland said that “to create the model and get it to work required developing new components for understanding how debris moves on a surface.” Some of this work could be applied more broadly to soil science, for example.
All of the code Strickland used to create his model will be available along with his paper, soon to be published. Other researchers can then tweak the code according to their needs.
Strickland shared there is more than one theory about the glacial features that lead to the formation of anthills. Are they the bottoms of old ponds or leftovers from crevasses and surface streams? Strickland believes the theory that they are the remains of old moulins.
Moulins are features reminiscent of continuously flushing toilets that form where a surface stream dives into the ice. Any debris too large to be transported by the subsurface stream flowing away from the moulin remains in place in a “plunge pool” at the bottom.
“[T]o create the model and get it to work required developing new components for understanding how debris moves on a surface.”
As the glacier shifts, stream flow changes. New moulins open up and old moulins lose their source of water. Without the water to continuously carve its shape, a dry moulin pinches closed. According to the ex-moulin theory, the anthill eventually forms when the surface ice melts down to the collection of debris flushed down to the bottom.
Strickland believes that the ex-moulin theory is supported by the presence of large boulders around the edges of anthills. Those boulders could be too large to be transported by streams but could fall down into a plunge pool. He also said he observed that anthills were commonly found in parts of the glacier that were riddled with moulins.
Since being interviewed last year, Strickland has made an effort to engage with the Copper Basin. He gave a presentation as part of the Wrangell Institute for Science and the Environment (WISE) lecture series. He is also hoping that local guides based in Kennicott and McCarthy can send him coordinates of anthills they find in their glacier travels.
Strickland is currently at the University of Kathmandu as part of the Sturgis International Fellowship.
This fellowship from the University of Arkansas is intended to support research, studying abroad, and collaborations. He is both learning from and assisting researchers there and taking on a support role in the field.
Meanwhile, Strickland is continuing to analyze the images he brought back from the Kuskulana glacier. Put simply, he’s “going to be doing some shapes and see where the water goes.”
