Trail Terms: Mountain Terrain

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View of Slide Mountain

Slide Mountain seen from Cornell Mountain

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Mountain Lingo Explained — Terrain

Let’s start with the basics. Because it turns out that even the most basic mountain terms are not at basic at all. Here are the 17 most common words and terms you’ll come across for mountain terrain.


We all know a mountain when we see one. At least, we like to think so.

But what if I told you: maybe not…?

For example, if you were asked to define the difference between a hill and mountain, how would you do it? Would you differentiate them by height? By volume? Steepness? Is prominence part of the equation?

The UK, the US, and the UN each use their own definition for the word “mountain”.

  • The British define a mountain as a summit of at least 2000’ (610m) — but prominence can also be factored in;
  • The US once defined a mountain as being 1,000ft or taller — but no longer does so;
  • The UN currently uses a sliding scale that combines height, grade and elevation change within a limited area.

In short, there is no universally accepted definition of “mountain“.

Dissected Plateau

Now consider that the Catskill mountains are not even mountains. We look at them as if they are, and climb them as if they are but, in fact, we’re climbing an enormous dissected plateau the slopes of which have been gouged out by glaciers and running water.

The Catskills were not formed by tectonic forces, but by erosion, so they are not mountains.

Summit, Peak, Sub-Peak

What constitutes a summit, a peak and a sub-peak also depends on whom you ask.

The International Climbing and Mountaineering Federation defines a mountain peak as having a prominence of at least 30 meters (98 ft) and a mountain summit as having a prominence of at least 300 meters (980 ft) — less than this means it’s classed as a sub-peak.


This leads to a discussion of topographic prominence which WikiPedia defines as a measure of, “The height of a mountain or hill’s summit relative to the lowest contour line encircling it but containing no higher summit within it.”

Quite the mouthful. But all this means is the difference in height between a mountain’s summit and the height of its key col. In practice, it means the least amount of elevation gain between the key col and the summit.

Col, Saddle, Notch

These are all names for the same thing, with regional differences. In the Catskills, as in the UK and Ireland, the most common term is “col” — except when we say “notch”.

A col is the lowest point on a mountain ridge between two peaks. The lowest point on the highest dip of the ridge is the key col.

A col is a natural mountain pass. If you had to climb over a mountain ridge, you’d aim for a col.

Cols are formed by glaciers. Two glaciers flowing in opposite directions carve out the mountain on either side, eroding toward each other until a saddle is formed. (Where three or more glaciers grind the mountain in multiple directions, you end up with a pyramidal peak, like The Matterhorn.)

A notch tends to be a steeper and more rugged kind of a col; generally, far too steep to drive a car.

In the Catskills, there are small notches like Jimmy Dolan Notch (between Indian Head and Twin) and Pecoy Notch (between Twin and Sugarloaf) and large saddle-like cols with broad flat sections like Mink Hollow Notch (between Sugarloaf and Plateau).

We also sometimes use the word “notch“ to describe the furrow leading up to the col — if the furrow seems sufficiently steep and rugged.


An arête is formed just like a col or notch, but is far steeper. The col between Wittenberg and Cornell is almost an arête. The Knife Edge route up to Mount Katahdin in Maine is a classic glacial arête.


A ridge is any long, narrow elevated section of land. Most mountains have several ridges leading up to their summit. Ridges often make the best routes up and down a peak.


A furrow is the opposite of a ridge: a long, narrow depression in the land. They are usually gouged out by glaciers or eroded by running water. They tend to be wet, with all the flora that goes along with wet places. In the Catskills, this means nettles.


A drainage is any furrow down which water flows. You often find several small drainages in a larger furrow. Typically, in the Catskills, drainages are full of debris, rocks and blowdown. Some are only active after rain. Some run more regularly due to springs further up the mountain.


A plateau is an area of relatively flat highland that is raised significantly above the surrounding area, often with one or more sides with deep hills. In the Catskills we have the two-mile-long flat ridge of Plateau Mountain, which is itself is part of the greater dissected Catskills plateau.


There are two massive cloves in the Catskills: Platte Clove and Kaaterskill Clove. A drive through either will reveal their character: deep, narrow gorges that cut through the surrounding rock landscape with dramatically steep cliffs on either side.

In spots, Kaaterskill Clove is 2500’ deep. Platte Clove is so steep and dangerous, and has been the site of so many accidents and deaths, part of it is known as The Devil’s Kitchen.


An escarpment is a long cliff that forms as a result of faulting or erosion. The result is two relatively level areas with distinctly different elevations. On the lower level there are few, if any, foothills. The Catskills Escarpment marks the eastern limit of the Catskills, which rise dramatically from the surrounding Hudson River flatlands.


The entire Catskill plateau is ancient seabed delta, essentially a vast level deposit of eroded rock and silt from long-disappeared mountains. It was laid down during the Devonian era (420-360 million years ago) just as the first forests were beginning to evolve.

Originally, in Pangaean times, the area now known as the Catskills was located well south of the equator.

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