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Navigation and safety

Talus

Also called boulder field, block field

What is talus?

Talus is a slope of large loose blocks, from roughly dinner-plate to car sized, that you cross by stepping from one rock to the next. The hazard is not sliding but a block that rocks or shifts under your weight, which is how ankles and legs get trapped.

Talus at a glance

Size
Dinner plate to car
Behavior
Individual blocks pivot
Pace
A fraction of trail pace
A field of large angular granite blocks, dinner-plate to car sized, crusted with pale green lichen and separated by deep dark gaps.
Talus: blocks big enough to stand on one at a time. The dark voids between them are the hazard, and that pale lichen is close to frictionless once it is wet.

How to move across it

Step onto the middle of a block rather than its edge, and put weight on gradually enough that you can take it off again. A block that rocks announces itself in the first fraction of a second if you are paying attention and not if you are committed. Experienced scramblers move deliberately with a low center of gravity and almost never hurry.

Trekking poles are a mixed blessing here. They help on the approach and on the flat sections, and they are a liability where you want your hands free on bigger blocks, because a pole wedged in a gap while you are falling is worse than no pole. Stowing them before the field starts is usually right.

Why it is so much slower than it looks

A talus field flattens out on a map and reads as easy ground. In practice a kilometer of it can take as long as five kilometers of trail, and it does so while demanding concentration the whole way. Trip plans that assume trail pace across a boulder field routinely arrive somewhere in the dark.

Wet talus and lichen-covered talus are substantially worse again. Lichen on granite is close to frictionless when damp, which is where a soft, sticky rubber compound earns its price over a harder hiking outsole.

What this means when you're choosing

  • A stiff enough midsole to stand on an edge without the shoe folding
  • A sticky rubber compound, which is what holds on wet lichen
  • Whether you can stow your poles quickly when you want your hands
  • Realistic time estimates, since talus is far slower than its distance suggests

The common mistake

Reading a boulder field as flat ground on the map

Contour lines say nothing about whether the surface is trail or a kilometer of blocks. Talus routinely runs at a fifth of trail pace and it is one of the most common reasons people end up finishing a day route by headlamp.

Common questions

How fast can you cross talus?

Assume a fraction of trail pace. A kilometer of boulder field can take as long as five kilometers of maintained trail, and underestimating that is one of the commonest reasons parties finish in the dark.

Should I use trekking poles on talus?

On the approach and flatter sections, yes. On larger blocks most people stow them, because you want your hands and a pole jammed in a gap during a fall makes the fall worse.

Where this is defined

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By Tom · Last reviewed . Back to the glossary