A person standing on Mount Timpanogos, Utah.
(Heber Davis/Unsplash)
When we picture glaciers, it's easy to imagine vast expanses of white ice gleaming under the sky.
But not all glaciers take that form.
The world is covered in a different kind, called rock glaciers – landforms in mountain regions where masses of ice and rock coexist, hidden under a hard surface of rock and boulders.
As a new study published in the Journal of Geophysical Research: Earth Surface reveals, rock glaciers can hold a truly stunning amount of ice.
There are more than 51,000 documented rock glaciers globally – over 10,000 of which are located in the US.
Despite their prevalence, though, these blanketed formations of ice are effectively hidden from sight under their dense covers of rock, so many people may never even know they're there.
(Bronson Cvijanovich/University of Utah)
"When we are high in the mountains and walking across loose rocks or rubble, you don't realize there could be 120 feet of ice buried beneath your feet," says glaciologist Leif Anderson from the University of Utah.
That natural rocky concealment helps preserve the ice in rock glaciers, insulating it from sunlight and heat at the surface, but it's also an obstacle for scientists.
One of the challenges of studying rock glaciers and learning more about them has been the difficulty of measuring the amount of water ice they contain, due to the rocky rubble that covers them.
In their new study, Anderson and fellow researchers figured out a new way to quantify the ice stores in rock glaciers, using Timpanogos Glacier at the base of Utah's Mount Timpanogos as their test subject.
While conventional imaging of glaciers can be done with ground-penetrating radar, the technique isn't effective for rock glaciers, as rocky debris mixed in with the ice scatters radio waves and degrades the image quality.
An alternative approach is to use a gravimeter, which can detect and map hidden masses underground.
"When we are high in the mountains and walking across loose rocks or rubble, you don't realize there could be 120 feet of ice buried beneath your feet," says glaciologist Leif Anderson from the University of Utah.
That natural rocky concealment helps preserve the ice in rock glaciers, insulating it from sunlight and heat at the surface, but it's also an obstacle for scientists.
One of the challenges of studying rock glaciers and learning more about them has been the difficulty of measuring the amount of water ice they contain, due to the rocky rubble that covers them.
In their new study, Anderson and fellow researchers figured out a new way to quantify the ice stores in rock glaciers, using Timpanogos Glacier at the base of Utah's Mount Timpanogos as their test subject.
While conventional imaging of glaciers can be done with ground-penetrating radar, the technique isn't effective for rock glaciers, as rocky debris mixed in with the ice scatters radio waves and degrades the image quality.
An alternative approach is to use a gravimeter, which can detect and map hidden masses underground.
(Bronson Cvijanovich/University of Utah)
"There is a large contrast in mass density between the rock that makes up Mount Timpanogos and the much lower-density ice that is in the rock glacier adjacent to it," says co-author and geophysicist Michael Thorne.
"When we measure the gravitational acceleration over the rock glacier, we see a larger decrease in that gravitational acceleration as we make measurements over areas with thicker ice."
With the data in hand from a survey of 232 measurements taken at different locations around Timpanogos Glacier, the researchers then developed a new method to image the ice in 3D within the rock glacier, using Bayesian statistics and modeling techniques to reconstruct the glacier's thickness, shape, and composition.
The results suggest that Timpanogos Glacier is made up of approximately 83 percent ice and 17 percent rocky debris by volume, with the ice occupying an average thickness of 18.8 meters (61.7 feet) across the rock glacier.
All up, the rock glacier contains approximately 1.5 million cubic meters of ice, roughly equivalent to the volume of the Great Pyramid of Giza (or about 600 Olympic swimming pools).
In terms of metric tons, that means Timpanogos Glacier holds about 1.4 million tons (1.5 million US tons) of ice hidden under its rocky surface, but the researchers didn't stop there.
With data from previous studies of other rock glaciers' internal structures, the researchers used their findings on Timpanogos Glacier to develop a new method that can estimate ice volume in rock glaciers from measurements of their surface area.
According to their calculations, the state of Utah as a whole holds about 1 billion tons (1 gigaton) of ice across all its 836 documented rock glaciers.
The western US contains almost 12 billion tons, and globally there's about 48 billion tons of ice stored inside rock glaciers.
It's a pretty incredible new way to gauge the amount of ice hidden inside rock glaciers around the world, and as the researchers say, it's important we keep refining our measurements of these huge formations.
"The need to quantify the water stored in these features is only increasing as glaciers respond to climate change and have the potential to transition to debris-covered glaciers and ultimately rock glaciers," the team writes.
"During periods of warming, rock glaciers can become destabilized and pose a threat to downstream infrastructure. Modeling these landforms in 3D can help to quantify their water stores and image their internal structure, allowing their impacts on local hydrology, ecology, and hazards to be better constrained."
"There is a large contrast in mass density between the rock that makes up Mount Timpanogos and the much lower-density ice that is in the rock glacier adjacent to it," says co-author and geophysicist Michael Thorne.
"When we measure the gravitational acceleration over the rock glacier, we see a larger decrease in that gravitational acceleration as we make measurements over areas with thicker ice."
With the data in hand from a survey of 232 measurements taken at different locations around Timpanogos Glacier, the researchers then developed a new method to image the ice in 3D within the rock glacier, using Bayesian statistics and modeling techniques to reconstruct the glacier's thickness, shape, and composition.
The results suggest that Timpanogos Glacier is made up of approximately 83 percent ice and 17 percent rocky debris by volume, with the ice occupying an average thickness of 18.8 meters (61.7 feet) across the rock glacier.
All up, the rock glacier contains approximately 1.5 million cubic meters of ice, roughly equivalent to the volume of the Great Pyramid of Giza (or about 600 Olympic swimming pools).
In terms of metric tons, that means Timpanogos Glacier holds about 1.4 million tons (1.5 million US tons) of ice hidden under its rocky surface, but the researchers didn't stop there.
With data from previous studies of other rock glaciers' internal structures, the researchers used their findings on Timpanogos Glacier to develop a new method that can estimate ice volume in rock glaciers from measurements of their surface area.
According to their calculations, the state of Utah as a whole holds about 1 billion tons (1 gigaton) of ice across all its 836 documented rock glaciers.
The western US contains almost 12 billion tons, and globally there's about 48 billion tons of ice stored inside rock glaciers.
It's a pretty incredible new way to gauge the amount of ice hidden inside rock glaciers around the world, and as the researchers say, it's important we keep refining our measurements of these huge formations.
"The need to quantify the water stored in these features is only increasing as glaciers respond to climate change and have the potential to transition to debris-covered glaciers and ultimately rock glaciers," the team writes.
"During periods of warming, rock glaciers can become destabilized and pose a threat to downstream infrastructure. Modeling these landforms in 3D can help to quantify their water stores and image their internal structure, allowing their impacts on local hydrology, ecology, and hazards to be better constrained."
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