New discovery about glaciers and landslides could help communities prepare for disaster  

For a scientist, the opportunity to witness and document something that has never been observed before is about as exciting as it gets. When an international research team that included Geology Professor Kelly MacGregor set out to examine a massive landslide that occurred on a glacier in Chilean Patagonia, what they found genuinely surprised them. The team recently published their findings in the journal Geology. 

Dr. MacGregor breaks down the new discovery and explains why, as the earth grows warmer, more knowledge about the way landslides affect glaciers is essential. 

Why did you choose to study this particular glacier, the Amalia Glacier in Chilean Patagonia?

We didn’t choose this particular glacier, this particular glacier chose us. There was a massive landslide on the Amalia Glacier in 2019, and there had been previous landslides in 1979 and 2017, so this is a glacier that is used to big rocks falling on it. The 2019 landslide was unique in that it was a massive one, about 262 million cubic meters of rock, and what was unusual about it is that instead of the rock covering the glacier, which is usually what happens, essentially the rock disappeared into the glacier. 

What are the study’s most significant findings?

There are two significant findings. First, nobody has ever seen rock from a landslide sneak underneath a glacier and mix in with the ice before.

The other big finding is really about how landslides affect glacier dynamics – how glaciers act once a landslide occurs. And in this particular case, when the giant landslide happened, it basically put up a barrier to the flowing ice above that point, but it increased the speed of the glacier’s flow below it. And what that means is that the terminus – the bottom end of the glacier – actually advanced out into the ocean by about a kilometer. Usually when we see glaciers advancing, we think the glacier is getting healthier and that it’s because the climate has gotten cooler or there’s more snow, right? But in this case, it advanced strictly because there was a gigantic landslide that occurred around it.

Why is it important to understand the way glaciers are affected by landslides? 

I think it’s interesting and important because as our climate warms, glaciers are retreating and getting thinner, and that means the mountains around them are effectively getting taller and steeper. So we expect way more of these landslides to happen on glaciers in the coming decades.  

The challenge – not with this glacier but with others – is that when there are people living downstream or downhill from them, there can be major consequences.

When rocks fall in places where there are glaciers, if we didn’t understand it, we might think the glaciers are behaving a certain way because of climate change. But it might, in fact, be because of this other outside event like a rock fall. 

Landslides around glaciers can cause things like outburst floods, which can be problematic for communities living nearby or downstream and in places where people, especially in parts of Asia and Scandinavia, use glacial meltwater for water resources and power production. In some places they can also cause tsunamis that may devastate local communities. When you have a landslide that messes up the whole system, it can destroy dams and change how glaciers deliver water. So understanding how a landslide happens and how it behaves is important to protecting communities from potential disasters. 

What was your role in the study?

My role on the team was as a glaciologist. It was my job to think about what the possible causes for the changes in glacier behavior might be. I provided guidance for the glacier modeling work and helped interpret the results, based in part on the high-resolution satellite images produced by the European Space Agency. 

What is the big picture takeaway for you? 

The big picture takeaway for me is that geologists tend to think about things in these very long timescales, but geology is also this very active process and it’s happening right now. And as climates change, the way that our world works is also changing.

What is it about glaciers that motivated you to devote most of your career to studying them?

When I was a kid, my parents used to drive us from Minnesota out to Montana, and it was so stunning to see the mountains just appear out of nowhere. For me, that was an emotionally and intellectually inspiring experience. I was also a cross-country skier in high school and college, and glaciers combined this love of these high mountainous landscapes and this interest in being on them and getting to move around them in all kinds of climate conditions. Plus, I like thinking about these longer timescales. I joked that when I was in graduate school, my Ph.D. dissertation was basically watching glaciers move. But that’s exactly what I did! I try to understand why glaciers operate the way they do and, if they do that over hundreds of thousands of years, how they shape and create these incredible landscapes.