Talus and Scree

Hiking off trail can be rewarding. But it’s a good idea to do it with as much safety knowledge and safety practice as possible.

Talus or Scree – Which is it?

Image via Wikipedia

Talus and scree are two geological features that informed hikers need to be well acquainted with. A search of dictionaries will reveal that these two geological terms are often considered synonymous. Each of these terms refers to loose rocks at the base of cliffs or steep mountain slopes. But, in layman’s terms, talus generally refers to larger stones and scree to smaller, looser stones. I’ll try to be a little more precise a bit further down concerning the difference. In any case, talus and scree can both be considered steeply-sloped piles of loose and potentially unstable rocks.

Geological Development of Talus and Scree Slopes

Over time, elements, including ice, sun, snow and gravity, do their work of fracturing and loosening the rocks of a cliff or steep mountain slope. The fractured materials fall, tumble or slide and become part of a talus or scree slope.

Hiking on Scree

A scree slope may be considered to be at its angle of repose. This is the theoretical angle where the forces that promote cohesion and stability in the mass of loose rocks are in perfect balance with the force of gravity that tends to pull the mass downward. The purpose of describing these forces is to direct your attention to a danger of instability. Such instability in the rocks can easily lead to a landslide or rockslide. So, be very careful hiking in scree. If your path takes you through a scree slope, move forward at a relatively flat angle. Switch back and forth repeatedly to ascend or descend. Watch out for other hikers in your “rock shadow”, the area below where your steps may send rocks sliding or tumbling down.

Do you like downhill skiing? Some people enjoy “screeing”? You guessed it – sliding down scree. If you’re tempted to engage in this esoteric sport, think twice. You could start a rock slide. Remember the “angle of repose” we talked about above? A scree slope, made up of stones from approximately the size of a grape to the size of a football, is by nature very unstable and always on the verge of sliding.

You may encounter trails built on scree. They’re not all that uncommon. If you’re hiking on one, be careful to keep your feet on the well-packed and groomed trail. A misstep could send rocks tumbling down – and possibly you with them. This can be especially dangerous for hikers who may be below you on another switchback. If you do happen to set a stone tumbling down, cry “rock!” really loud. If you hear someone above you cry “rock!”, crouch and protect your head. Never make such a yell as a joke.

A Balancing Act

Talus, scree’s bigger cousin, can be considered rocks ranging in size between that of a football and a car. Anything larger can be referred to as a boulder. Now, someone, or anyone could disagree with these definitions. But, remember that they are kind of squishy as far as the size goes. The size boundaries between scree and talus and between talus and boulders is blurred. There’s no way of being more precise. Trying to give more precise definitions wouldn’t be helpful.

Walking or hopping on talus or boulders is a balancing act that may prove very exhilarating. Hopping from rock to rock can be fun. But watch out. Breaking a leg in such an environment could engender a risky rescue operation and ruin your whole day. Don’t try boulder hopping without boots with good sole grip and ankle support. Another bit of good advice is to forget about engaging in boulder hopping if your boots are wet of the boulders are wet or icy.

Make it your determination to hike safely, especially off-trail. ~Richard Davidian, Ph.D.

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