Slope Angle on Non-Snow Terrain

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Robbie Crouse
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Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

So it's couloir season and there's always lots of stuff on slope angle as it regards steep snow or avalanche terrain ... but it got me thinking that I never think about slope angle when there's no snow. For example, fifth class is often going to be near vertical, but I was just curious if there was an average for when class 2 terrain generally is class 3 terrain in regards to slope angle. I looked up my tracks on caltopo and here are a few examples:

-the last 1000 ft of climbing at the Crestone Needle was an average of 39 degrees with a max of 57 degrees

-the west ridge on Pacific Peak averaged 40 degrees with a max of 56 degrees

-Ellingwood SW ridge was average of 29 degrees with a max of 54 degrees

There's probably not a clear line of demarcation in dry terrain -- snow smooths out the angle so it's more consistent (vs. something like slabs) -- but I was curious if anyone else ever paid attention to this before. (For example, it could be a problem with my tracks but I was surprised Ellingwood's SW ridge wasn't as steep).

-Robbie
Last edited by Robbie Crouse on Fri May 21, 2021 7:46 am, edited 1 time in total.
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Dave B
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Re: Slope Angle on Non-Snow Terrain

Post by Dave B »

Knife edge on Capitol is pretty much flat and is 3-4th class.

Flatirons are lotsa 5th class and lotsa 50-70 degrees.

Angle has less to do with class rating than difficulty of moving through said terrain, and potential consequences of a fall.
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

Sure Dave, steepness alone doesn't determine class; I didn't say it did. Otherwise flat terrain might equally be class 1 or 5. Surely you aren't suggesting that? How many class 1 seventy degree routes do you know? So notice that I was talking about averages and what is often the case. Class 5 terrain is generally close to vertical; I stand by that. My main question is about when class 2 hiking moves into class 3 scrambling in regard to slope angle.
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Re: Slope Angle on Non-Snow Terrain

Post by ekalina »

I'll throw out a number here...I think we could not have a Class 2 route at an angle that exceeds about 45 degrees, and here's my (theoretical) argument.

Class 3 means that hands are needed to facilitate upward progress. On a sloped surface, the force due to gravity, which is always directed towards the center of the earth, can be broken down into two components – one that is parallel and another that is perpendicular to the slope. At a 45 degree angle, these two components are equal in magnitude, which means that there is as much force directing you down the slope as there is keeping you on it. Hence, I think you would need to use your hands to resist the force due to gravity that is directing you down the slope.

I am not sure how to account for the frictional force in this argument. Depending on the material on this slope, there might be little to no friction (ball-bearing type rock mixed with dirt tends to immediately slide down when you step on it), so maybe we can neglect the frictional force, but I'm not sure.

Note that I'm not saying a C3 route must be 45+ degrees. That is clearly not the case. I'm only arguing that you couldn't have a C2 route that is 45+ degrees. Maybe someone can find a C2 route that debunks my argument.
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Re: Slope Angle on Non-Snow Terrain

Post by nunns »

Going from memory, it seems like there might be a chart in Roach's 14ers book. That may be for snow though.

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Re: Slope Angle on Non-Snow Terrain

Post by aholle88 »

We often joke about “class 3 grass” in a certain mountain range because the approaches to the ridges are fairly steep at times. I don’t think anyone would actually consider a slope consisting of grass/talus/scree actual class 3 though. It’s simply not. It’s just miserable, and joking when you are in misery is the key to success and longevity in the mountains :lol:
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Re: Slope Angle on Non-Snow Terrain

Post by justiner »

Oh there's plenty of Class 1 trail segments where the rise is equal to the run - it's just called, "rock stairs".

Likewise, there's plenty of Class 5 pitches that just don't ascend/descend at any appreciable amount - those are just traverses.



Extreme example, I'll grant you, but much of the Class 3 of the Keyhole route is just a tracverse - the Narrows, for example doesn't change elevation all that much.
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

ekalina, yeah, I think 40+ puts one into a "most likely class 3" -- where the definition of class 3 is something like "constant use of hands for forward progress" (class 2+ being "occasional use of hands, primarily for balance" and class 4 is "searching and testing handholds"). A number of my favorite class 3 routes averaged about 40 degrees when I checked them on caltopo. There were some surprising ones in the 20s and some as high as upper 50s.

Sean, yeah, that chart from Roach was something I thought of in all this. Here's his ratings:

Easy: 0 - 30 degrees
Moderate: 30 - 45 degrees
Steep: 45 - 60 degrees
Very Steep: 60 - 80 degrees

A number of "snow" routes are also the standard non-snow routes, like the Crestone Needle south gully; it's a "moderate" snow climb and a class 3 dry climb.

aholle88, I've encountered some class 3 grass! Not exactly a "traditional" class 3 route, but I call "grass crawling" since I'm basically on all fours in a really awkward position.
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Robbie Crouse
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

Hey Justin,

Thanks for the great video link. Yeah, I wasn't really talking about traverses, just slope angle. The Dawn Wall is definitely not a low slope angle, lol. Even on traverses, what generally makes them more difficult / exposed is the steep slope around it. Would the Broadway move around the boulder be a big deal if it was along a gentle a 15 degree slope?

Good point on the rock stairs / steep maintained trails that are class 1. I guess at some point, though, even a stairs is steep enough that you need to "climb" it with the aid of hands.

On the Keyhole route, I just checked the Homestretch and on caltopo at least it averages 48 degrees with a max of 57 degrees. That seems pretty consistent with the other class 3 angles. On the Narrows, you're right that you are traversing, but it's 54 degrees on the steepest part around it.

-Robbie
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Re: Slope Angle on Non-Snow Terrain

Post by Alpine Guy »

Kelso Ridge might be a good example of a minimum slope angle for a class 3.
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

It makes sense that class 3 climbs that are ridges might be less steep on the route itself, but are often steep on either side. They are more exposed than a direct face.
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Re: Slope Angle on Non-Snow Terrain

Post by letitbeirie »

Robbie Crouse wrote: Fri May 21, 2021 12:24 pm On the Keyhole route, I just checked the Homestretch and on caltopo at least it averages 48 degrees with a max of 57 degrees. That seems pretty consistent with the other class 3 angles. On the Narrows, you're right that you are traversing, but it's 54 degrees on the steepest part around it.
Wow it's really that steep? I think freeway on the second flatiron averages about 48 too, but it's class 4 or low 5, depending on who you ask.
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