Science & Technology

Alaska’s ice-rich slump rock glacier canary

Emily Schwing: this is Scientific American60 seconds of science. This is Emily Schwing.

How do you fight uphill battles when the problem is downhill?It’s just a resident geologist in Denali National Park Denny Caps I’m trying to understand.

cap: In recent years, Pretty Rocks landslides have really turned into our top priority, due to minor maintenance concerns.

Schwing: On a refreshing autumn day in September, just inside the park entrance, nothing is happening in the office. The staff here has been pushing the park button for the winter for a week. But in what’s known as Pretty Rocks, more than 40 miles down the park’s only road, things actually go downhill up to 0.5 inches an hour.

Paul Olig: Pretty Rocks landslides act more like glaciers than what most people consider to be landslides.

The Pretty Rocks slump time lapse image is a slump from July 21st to August 25th, 2021. During this time, the road was off by 21 feet. credit: National Park Service Geological Team

Schwing: Paul Olig Denali’s interpreter and director of education.

Orig: It is this highly ice-rich material that responds to temperature fluctuations and speeds up or down based on a variety of factors, including ice levels and ice temperature. As a result, Pretty Rocks landslides tend to be considered more like rock glaciers than what is normally considered a landslide.

Schwing: Landslides give a hint of what else will happen to the entire US national park system, Olig said.

Orig: In my view, this is a kind of “coal mine canary” type situation and we are at the forefront of these climate change effects. But as we look at these more and more, more parks will face other challenges that may be as difficult or even more difficult to understand.

Schwing: Here in central Alaska, much of the ground appears to be frozen semi-permanently for most of the year. But Denny Caps says the signs of climate change here are obvious for years.

cap: Denali is a really great place to understand what the future looks like. Also, due to temperatures over the past few years, the location here and in the park has already reached the 2040 forecast. So we far exceed existing projections of climate change here in the park. So it really gets our attention.

Schwing: At Pretty Rocks, road conditions changed so much by the end of this summer season that park officials eventually closed the road to a visitor center with direct views of North America’s tallest mountain and wilderness lodges. Access has been blocked. And Pretty Rocks isn’t the only one keeping Denny Capps busy.

cap: Yes, that’s certainly not the case. It’s all up and down the park road we’re challenging with permafrost. There is a system called an unstable slope management program. The program tracks over 140 volatile slopes above and below park roads. Currently, not all of them are necessarily conditioned by permafrost, but many of them are.

Schwing: Speaking of 140, it seems that there are quite a lot of places that the park pays attention to.

cap: It’s a relatively high number, but I want to make sure that it’s not always in a reactive position. And some of those sites have very small maintenance issues. As you know, you may have had to do some dirty work in the past. And we are watching all the way to Pretty Rocks. There is something like a large mass of sales that is causing road closures. As a result, the magnitude and frequency of impacts of all ranges of severity and type occur entirely.

Schwing: So what is causing this move? Temperatures rise throughout the year and summer rainfall increases. This all melts the once frozen ground.

cap: I know I’ve seen more heavy rainfall and floods. During the decade I was here, several rainfall records were set, including very heavy rainfall. Alaska’s long-term meteorologists have stated that there is the highest daily rainfall outside the coast, with a history recorded here last year. This is the north side of a relatively dry mountain, with many terrain undulations and a melted permafrost layer. If it rains at that level, it can be catastrophic for us.

Schwing: It’s like pouring hot water on ice cubes.

cap: Really so. And that’s one of the things we are aware of. This is very important. This rain, especially the temperature of that rain. Everyone knows that with warm air, you can do it. Certainly warms things up. But if you have warm water, it actually carries more heat, and it lowers that heat to the ground. So we are really recognizing the importance of the amount and temperature of rainfall in these sensitive areas.

Schwing: Many of Denali National Parks are designated as wilderness, so long-term solutions are limited.

cap: Unfortunately, I don’t want to experiment much here. You know, this is a sensitive place. So, for example, elsewhere, instead of filling with gravel to build a road, you can put Styrofoam underneath because it insulates the ground and is much lighter. But I don’t want Styrofoam to come out into the environment here and let the plastic fall into the river forever.

So we are in the process of deciding exactly what to do in these places. But in general, we at Pretty Rocks will probably fill the landslide there. This is one of the classic ways to deal with all these kinds of geological hazards. If you have a bull rushing at you, you set aside and let it go. You do not square your shoulders and try to stop it. And that’s essentially what we’re trying to do at Pretty Rocks — we’re trying to do it.

Schwing: Denali is the third largest national park in the United States. There are also two larger sizes in Alaska. The Arctic Gate and Langersent. Elias. And even there, there is a danger that a large band of permafrost will melt. From Paul Ollig’s point of view, with an emphasis on educating and informing the general public, he says there may be a silver lining.

Orig: Having a specific infrastructure like a potential bridge over a landslide like Pretty Rocks is the perfect tool for us to use. At the same time as challenging, I have very specific items to put together a conversation about the effects of climate change, talk about solutions, and talk about what the park needs to adapt to changing conditions. Give to us.

Schwing: Park officials are working on a $ 55 million bridge plan over the upset part of the Pretty Rocks road. Construction may begin as early as next summer. Now that autumn has begun and the park has had its first snowfall, there is little to do but watch over.

cap: We are really interested in how it reacts during the winter. So last spring, when the spring road opened in late March, a cliff of about 18 feet fell. Therefore, there is already an 18-foot vertical cliff at that location. Therefore, we can certainly expect big challenges next spring.

Schwing: As is usually the case in Alaska, it is never clear what snowmelt will reveal when the warm weather returns the following year.

For 60 seconds of science, I’m Emily Schwing.

[The above text is a transcript of this podcast.]

Alaska’s ice-rich slump rock glacier canary Alaska’s ice-rich slump rock glacier canary

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