When building sandcastles and tunnels in the summer, dig safely – collapsing sand holes can cause suffocation or even death
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When building sandcastles and tunnels in the summer, dig safely – collapsing sand holes can cause suffocation or even death

While millions of Americans vacation at the beach every year to seek out sun, sand, and ocean, many may not realize how dangerous digging holes in the sand can be. In February 2024, a 7-year-old girl died when an approximately 5-foot (1.5-meter) hole she and her brother had dug in the sand collapsed on top of her, burying her alive.

As a coastal scientist who has studied beaches for many years, I was called in to help investigate the girl’s death. While many people nearby stepped in to try to free the girl after the hole in the sand collapsed, local firefighters were unable to arrive until several minutes after the incident – ​​too late to revive the victim.

In February, a little girl suffocated in Lauderdale-by-the-Sea, Florida, when a sand pit collapsed on her.

Digging holes in the sand may seem innocent, but if the hole is deep enough and collapses on you, escape is extremely difficult. In fact, studies suggest that more people die from suffocation in sand than from shark attacks.

Sand Basics

Sand is not actually a type of material. It is a size category of material, from 0.0025 to 0.08 inches (0.06 to 2 millimeters) in diameter. The type of sand is determined by the materials from which it is made. Quartz sand, composed of silicon dioxide, is the most common sand found on beaches, except on tropical coasts, where there are coral sand beaches, composed of calcium carbonate.

Material coarser than sand is not soft to the touch – it is not suitable for building solid sandcastles. Silt and clay, which are finer than sand, make the water cloudy and are commonly called mud.

The weight of sand depends on the materials from which it is made. Pure quartz beaches, which have very white sand, weigh about 90 pounds per cubic foot when dry.

But most beaches contain a mix of minerals, which creates a tan or bronze. The minerals that darken the sand are much heavier—the sand on most beaches would weigh up to 130 pounds per cubic foot when dry.

Dry, loose sand grains will form a pile with an angle of inclination of about 33 degrees, called the angle of repose. The angle of repose is the sharpest angle at which a pile of grains remains stable, and the frictional force between each grain determines that stability.

When building sandcastles and tunnels in the summer, dig safely – collapsing sand holes can cause suffocation or even death
The angle of repose describes the slope of the pile of sand.
Davius/Wikimedia Commons, CC BY-SA

Sand is more stable when wet because the surface tension between the water and the sand grains can hold the pile of sand in place vertically. But when it dries out, the pile will collapse because there is no longer surface tension.

So if you dig a hole in the beach, it will remain stable as long as the sand stays wet. When it dries out, the hole will collapse.

Sand is unstable

When the sand that makes up the hole dries out or someone stands close to the edge of the hole, adding extra weight, the hole collapses and the heavy grains fill all the open spaces in the hole. As a result, the trapped person no longer has air to breathe.

Skiers trapped by avalanches can cup their hands to form an air cup because the snow is light, but this is not possible when sand slides.

Rescuing someone from a collapsed sand pit is very difficult because the sand is heavy and unstable. As rescuers shovel sand to free the victim, the pit will continue to collapse under their weight and fill with sand again. Rescuers only have about three to five minutes to rescue a person trapped in a sand pit before they suffocate.

Professionals, such as firefighters, place boards across the opening when rescuing someone from a collapsed sand pit. That way, they can reach down and use tools to remove the sand without putting any weight directly on the edge of the hole.

Experts recommend never digging a hole deeper than the knees of the shortest person in the group – the maximum depth is 2 feet (0.6 meters).

To save someone in a collapsing sand pit, focus on exposing their mouth and removing sand from their upper chest. If you can exposing their mouth, you can administer artificial respiration while other rescuers continue to dig out their chest.

Too many people crowding into a sandbox can do more harm than good. Only two or three rescuers should work in the immediate vicinity of the victim, while others work to remove sand from the wider excavation area, making it easier for those in the center to remove sand. Those on the outer perimeter can remove sand from the central area, using anything available, from buckets and shovels to beach chairs and boogie boards.

A long, narrow hole in the sand about two feet deep.
A sand pit formed by a land collapse in New Jersey.
Stephen Leatherman

Case study

Collapsing sandboxes led to the deaths of 31 people, mostly children and 87% male, between 1997 and 2007 in the U.S. During this period, there were 21 reported cases of sandbox collapses that survived, although many of them required cardiopulmonary resuscitation.

The ages of the sand hole collapse victims ranged from 3 to 21 years. The holes were typically 2 to 15 feet (0.6 to 4.6 meters) in diameter and 2 to 12 feet (0.6 to 3.7 meters) deep. Digging, tunneling, jumping, and falling into the hole all inadvertently caused the collapse.

These sinkholes can happen suddenly and in situations that most people would not consider dangerous. Next time you visit the beach, be sure to look out for holes in the sand and fill any as soon as possible. Even a shallow hole can injure someone who falls into it.