Rock Climbing Safety – Beware of Falling Rocks!

Preface:

On September 27 and 28, 2017, large-scale rockfalls occurred consecutively at El Capitan in Yosemite National Park, California, USA, resulting in at least one fatality and two injuries.

Looking back to 2013, two climbers lost their lives a week apart while ascending El Capitan due to smaller rockfalls. Eighteen years ago, a rockfall at Glacier Point in Yosemite also claimed one life.

While we mourn the deceased, as climbing enthusiasts, we must remain vigilant. Safety is always the most critical issue we face. Before enjoying the thrill of climbing, we need to understand which geological formations and rock conditions are suitable for climbing, as well as the necessary safety precautions during the ascent.

I. Rockfalls and Their Causes

A rockfall refers to rock fragments detaching from a nearly vertical cliff due to chemical or physical processes and falling freely under gravity, either bouncing, sliding, or rolling down.

Thus, rockfalls require two essential conditions: Steep Cliffs and Loose Rock Fragments.

For climbers, steep cliffs are not only unavoidable but also the very challenge we seek. Therefore, the key to avoiding rockfalls lies in choosing routes where rock fragments are less likely to detach.

The likelihood of rock fragments detaching depends on the geological structure of the rock mass and external environmental factors.

Air and water are the primary external agents causing rock weathering and detachment.

Long-term exposure to air circulation, surface water, or groundwater can lead to the formation of rock fragments, especially in rock masses prone to erosion, such as those composed of sandstone or shale.

For example, the cliffs in Moab, Utah, USA, are primarily sandstone.

In contrast, harder rocks like basalt, granite, and metamorphic rocks (e.g., marble) are less susceptible to weathering under similar conditions, making rockfalls less likely.

The climbing paradise of Chamonix, France, is predominantly granite.

If a rock mass contains an unconformity—a distinct boundary between different types or ages of rock—the rocks on either side of the boundary are more likely to detach, creating loose fragments.

For instance, in Death Valley, California, USA, the contact between conglomerate (dark upper layer) and marble (light lower layer) forms an unconformity.

• Animal or plant activity can also contribute to rock fragmentation.

Burrowing animals (e.g., rabbits) may use rock crevices as nests, widening cracks and eventually splitting the rock.

Root wedging is another cause of rock fragmentation. In areas with ample precipitation, water retained in rock crevices can promote plant growth. As roots grow deeper, they can exert pressure and split the rock, creating loose fragments.

• Natural climate changes can accelerate rock fracturing.

For example, recent rockfalls in Yosemite were attributed to temperature fluctuations during the transition from summer to autumn, causing thermal expansion and contraction of the rocks. In cold, wet regions, water freezing and thawing in rock crevices can also hasten fracturing.

• Beyond physical processes, chemical weathering can produce rock fragments.

Oxygen in the air, acidic precipitation (acid rain), salt in seawater, or minerals in lakes can react with the minerals in rocks.

These chemical reactions may alter the grain size of the rock’s internal structure, changing its morphology and creating loose fragments.

The karst landscape of Guilin, China, is a result of limestone chemical weathering.

Once a rockfall begins, the initial falling debris can exert force on other rocks, dislodging or striking them and triggering larger-scale rockfalls.

For example, in Yosemite, the second rockfall was ten times larger than the first. For safety, climbers should avoid areas prone to rockfalls.

II. Preventive Measures

To effectively avoid rockfall-prone areas and minimize human-induced rockfalls during climbs, climbers can take the following steps:

• Research the route thoroughly before climbing. Understand the rock composition and avoid routes with highly unstable rock masses.
• Choose the right time to climb, avoiding seasonal transitions. Test the stability of handholds and footholds before climbing, and identify loose rocks. Avoid using unstable holds whenever possible. If necessary, apply downward force vertically, never pull horizontally.
• Tap questionable holds to check for hollowness. Hollow rocks produce a crisp sound, while solid rocks sound dull or make no noise. Hollow rocks are highly prone to breaking under force and should be avoided.
• Monitor rope placement during ascent or descent. Rope movement or force on the rock can dislodge debris or trigger rockfalls.

It’s worth noting that rockfalls are a common natural phenomenon. Yosemite National Park records over 80 significant rockfalls annually, with countless smaller ones going unrecorded.

Therefore, for outdoor climbers, avoiding rockfall-prone areas and taking preventive measures are essential. Additionally, learning how to respond to rockfalls during climbs is crucial for safety.

If a rockfall occurs while climbing:

• Stay calm and control your body and emotions. Adjust your breathing and assess whether you are injured.
• Evaluate your surroundings to ensure you are in a safe spot, away from falling rocks.
• Anchor yourself to the wall using any available gear.
• Check on your climbing partners to confirm their status and location.
• Carry a phone for emergencies or use a radio to call for help. If no devices are available, shout for assistance, wave brightly colored clothing, or use a flashlight to signal rescuers.

By staying prepared and vigilant, climbers can minimize risks and enjoy a safer climbing experience.