4 ms·

I have a collection of climbing magazines from the 1990s, and many of the featured routes in South American ranges like the Cordilla Blanca are no longer climba

I have a collection of climbing magazines from the 1990s, and many of the featured routes in South American ranges like the Cordilla Blanca are no longer climbable today. The glaciers, ice, and snow are gone, and what's left is crumbly, friable rock that is not safe to climb on. Mt Rainier is also mostly composed of crumbly, friable rock, and I wonder just how climbable it would be without glaciers and snowfields to provide secure footing and keep rocks from falling down on people.

hodgesrm 7y ago
Rockfall has always been part of the fun of climbing on the upper parts of Mt Rainier. The practical effect of warming is that the season where you need to worry about it is now extended. What's more worrying is the possibility we'll see some major collapses. Many of the big features on Rainier like Gibraltar Rock and the Willis Wall are anchored by ice at the base. As this disappears those structures may become unstable. It's conceivable that collapse could trigger lahars, which are a big risk for people in the valleys below the mountain. In the past these have run all the way out to Puget Sound.
- snowwrestler 7y ago
  I doubt that the gravitational collapse of a rock buttress, even a large one, would be enough to trigger a major eruption of Rainier. The energy of an eruption is shockingly large and almost anything else you can imagine pales before it. The thickness and weight of the entire mountain is not a significant check on an eruption; therefore, it doesn't seem likely that removing a portion of the mountain (via collapse) would do more than vent some steam and noxious gases. Eruptions depend on what happens deeper in the crust, as I understand it.
  - hodgesrm 7y ago
    Lahars are different. They are mudflows. It's common to see them triggered by eruptions (e.g., Mt St Helens in 1980) but they can arise from landslides as well as glacier collapses. The most recent Lahar on Mt Rainier was in 1947. [1] [1] https://en.wikipedia.org/wiki/Kautz_Creek https://en.wikipedia.org/wiki/Kautz_Creek
    - snowwrestler 7y ago
      Thanks. I thought the term was reserved for hot mudflows triggered by an eruption, but I can see that you are correct.

hodgesrm 7y ago

Rockfall has always been part of the fun of climbing on the upper parts of Mt Rainier. The practical effect of warming is that the season where you need to worry about it is now extended. What's more worrying is the possibility we'll see some major collapses. Many of the big features on Rainier like Gibraltar Rock and the Willis Wall are anchored by ice at the base. As this disappears those structures may become unstable. It's conceivable that collapse could trigger lahars, which are a big risk for people in the valleys below the mountain. In the past these have run all the way out to Puget Sound.

snowwrestler 7y ago
I doubt that the gravitational collapse of a rock buttress, even a large one, would be enough to trigger a major eruption of Rainier. The energy of an eruption is shockingly large and almost anything else you can imagine pales before it. The thickness and weight of the entire mountain is not a significant check on an eruption; therefore, it doesn't seem likely that removing a portion of the mountain (via collapse) would do more than vent some steam and noxious gases. Eruptions depend on what happens deeper in the crust, as I understand it.
- hodgesrm 7y ago
  Lahars are different. They are mudflows. It's common to see them triggered by eruptions (e.g., Mt St Helens in 1980) but they can arise from landslides as well as glacier collapses. The most recent Lahar on Mt Rainier was in 1947. [1] [1] https://en.wikipedia.org/wiki/Kautz_Creek https://en.wikipedia.org/wiki/Kautz_Creek
  - snowwrestler 7y ago
    Thanks. I thought the term was reserved for hot mudflows triggered by an eruption, but I can see that you are correct.