This article is republished from The Conversation, an independent and nonprofit source of news, analysis and commentary from academic experts. Stephen P. Leatherman is Professor of Coastal Science at Florida International University.
While on beaches every year to seek out sun, sand and the sea, many might not realize how dangerous digging holes in the sand can be. In February 2024, a after an approximately 5-foot (1.5-meter) hole she and her brother dug in the sand collapsed in on her, burying her alive.
As a who鈥檚 been studying beaches for many years, I was called in to help investigate the girl鈥檚 death. While many people nearby stepped in to try to free the girl after the sand hole collapsed, local firefighters couldn鈥檛 arrive until 鈥� too late to resuscitate the victim.
Digging holes in sand might seem innocent, but if the hole is deep enough and collapses on a person, it is extremely difficult to escape. In fact, research suggests from sand burial suffocation than from shark attacks.
Sand basics
Sand isn鈥檛 actually a type of material. It鈥檚 a category of material size, 0.0025 to 0.08 inches (0.06 to 2 millimeters) in diameter. The is determined by the materials making it up. , made up of silicon dioxide, is the most common sand found on beaches, except at tropical coasts where coral sand beaches, made up of calcium carbonate, are found.
Material coarser than sand is not soft to the touch 鈥� it . Silt and clay, which are finer than sand, make water murky and are commonly called mud.
READ MORE: A girl dies after a sand hole on a Lauderdale-by-the-Sea beach collapses
Sand鈥檚 weight depends on the materials it鈥檚 made of. Pure beaches, which have very white sand, weigh around 90 pounds per cubic foot when dry.
But most beaches contain a mixture of minerals, creating a tan or brown appearance. The minerals that darken the sand are much heavier 鈥� sand on most beaches would weigh up to 130 pounds per cubic foot when dry.
Dry, loose grains of sand will form a pile with a slope angle of about 33 degrees, termed its . The angle of repose is the steepest angle at which a pile of grains remains stable, and the between each grain determines that stability.
Sand is more stable when it鈥檚 wet because the between water and sand grains can hold the pile of sand in place vertically. But once it dries, the pile will collapse, as there鈥檚 no more surface tension.
So if you dig a hole in the beach, it鈥檒l stay stable for as long as the sand stays moist. Once it dries, the hole collapses.
Sand is unstable
When either the sand forming the hole dries out or someone stands near the edge of the hole, adding extra weight, the sand hole collapses in, and the heavy grains fill all open spaces in the hole. This leaves no air available for a trapped person to breathe.
While skiers trapped in avalanches can cup their hands because snow is light, but that鈥檚 not the case when sand collapses.
Rescuing someone from a collapsed sand hole is very difficult because sand is both heavy and unstable. As rescuers scoop away sand to free the victim, the hole will continue to collapse under the rescuers鈥� weight and refill with sand. Rescuers have only to save a person who is trapped in a sand hole before they suffocate.
READ MORE: Experts say more affordable access to swim lessons is key to reducing child drownings
Professionals like firefighters will place boards across the hole when rescuing someone from a sand hole collapse. This 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 knee height of the shortest person in your group 鈥� with 2 feet (0.6 meters) being the maximum depth.
To rescue someone in a collapsing sand hole, focus on exposing their mouth and removing sand from on top of their chest. If you expose their mouth, you can administer while other rescuers continue digging out their chest.
Too many people crowding a sand hole rescue can cause more harm than good. Just two or three rescuers should work in the victim鈥檚 immediate area while others work on clearing sand away from the wider excavation area, which makes it easier for those in the center to remove sand. The people on the outer perimeter can clear sand away from the central area using anything available, from buckets and shovels to beach chairs and boogie boards.
Case studies
Collapsing sand holes , mostly kids and 87% male, from 1997 to 2007 in the U.S. During that period, were in a reported sand hole collapse but survived, though many required CPR.
Victims of sand hole collapse have . The 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 have all inadvertently triggered collapse.
These collapses , and in situations that don鈥檛 seem dangerous to most. During your next trip to the beach, make sure to keep an eye out for sand holes and fill all holes as soon as possible. Even a shallow hole can injure someone who stumbles into it.
