A sinkhole, otherwise called a cenote, sink, sink-opening, swallet, swallow opening, or doline, is a downturn or opening in the ground brought about by some type of breakdown of the surface layer. Most are brought about by karst measures – the compound disintegration of carbonate rocks or suffosion measures.
Sinkholes are a common feature in Florida’s limestone-rich bedrock as groundwater easily dissolves the calcium carbonate into solution turning the ground into a slushy mix that washes out under the structures built on top of it.
The Black Holes are a group of water-filled pits in the waters of the Bahamas. These circular sinkholes are darker in color than the surrounding water because of a layer of microorganisms that ‘swallow’ the light.
Most sinkholes give warning signs of their impending devastation.
‘Blue holes’ refers to the deep, water-filled pits that have formed in carbonate rocks and create a deep blue color.
Sinkholes form when water dissolves minerals in the bedrock leaving the structures on top of the ground sitting precariously on loose soil that can quickly wash away.
Cenotes are the sink holes in the waters of the Yucatan Peninsula in Belize, where limestone deposited in the shallow water.
If a sinkhole is in the process of forming the structures on top of it can give a hint to its existence: for example, slumping or sagging fence posts, and trees that start to lean. More subtle signs can include doors and windows that don’t close properly.
The Sotanos are sinkhole pits in Mexico.
Heavy rains can trigger the collapse of a sinkhole that had been slowly forming earlier.
Tiankeng refers to the very large sinkholes that are often the result of underground caverns collapsing. Tiankeng means ‘sky hole’ in Chinese, and most of these large sinkholes are found in China.
When rainfall collects in an area where water previously did not collect, that is another sign that the land is subsiding.
In New Zealand the term ‘Tomo’ refers to potholes in karst regions.
When tropical storm Agatha blew through Guatemala in 2010, the volcano-pocked nation witnessed the worst kind of sinkhole form in the middle of Guatemala City: a 100-foot deep, 66-foot wide circular chasm called a “piping feature.”
The largest sinkholes are found all over the world, including those found in Africa, Asia, the Caribbean, Central America, Europe, North America, South America, and Oceania.
If a sinkhole is caught early, cities can inject grout into the hole to rebuild a foundation over the degrading bedrock.
The Dragon Hole in Asia is the deepest known underwater sinkhole on earth.
In Mexico, many sinkholes called cenotes expose these underground rivers and show the location of underwater limestone caves.
The deepest water-filled sinkhole in the world is Zacaton, located in Mexico. Its depths reach 1,112 feet.
Blue holes along low-lying coastlines are the remnants of sinkholes formed during past ice ages when sea level was 300 to 400 feet lower than today.
Winter Park Sinkhole in Florida appeared in May of 1981 and is now referred to as Lake Rose. It is 350 feet in width and 75 feet in depth and one of the largest to form in recent history in the U.S.
SCUBA diving in a blue hole can be dangerous as the depth is difficult to judge with just your eyes.
New Zealand’s Harwood Hole is 600 feet deep. It is a sinkhole located in Abel Tasman National Park.
Sinkhole insurance is offered in Florida.
The largest sandstone sinkhole in the world is Sima Humboldt, located in Venezuela, at 1.030 feet in depth. This sinkhole has vertical walls and a forest at its bottom floor.
Sinkholes are nearly impossible to predict.
Florida is a common place for sinkholes too occur. The bedrock is limestone and easily dissolved by groundwater, resulting in dissolved ground. They are not usually deadly but people have been swallowed up – including one man who was in bed when his house disappeared.
Sinkholes can form gradually or suddenly, even without warning.
A sinkhole can be stopped if caught on time. Injecting grout into the developing hole can save the structures above if they are caught early enough.
Sinkholes can form when the rain and floodwaters brought by hurricanes start to recede.
Signs of a sinkhole under a building such as a house include windows and doors that refuse to close properly, sagging fence posts, leaning trees, or rain water beginning to collect in a spot on the ground where it never used to collect.
Frequently Asked Questions About Sinkholes
Sinkholes are often dramatic occurrences that can cause significant damage. Here are some FAQs to shed light on these fascinating, yet potentially hazardous, geological phenomena:
- What is a sinkhole?
A sinkhole is a depression or hole in the ground that forms when the underlying rock or soil collapses. They can vary greatly in size, from a few feet wide to acres across, and depth, ranging from shallow dips to hundreds of feet deep.
- What causes sinkholes to form?
The primary culprit behind sinkholes is the erosion of soluble bedrock, most commonly limestone. Rainwater dissolves the rock over time, creating cavities and underground channels. When the overlying soil loses support, it collapses, forming a sinkhole.
Other factors can also contribute to sinkholes:
- Human activity: Activities like withdrawing large amounts of groundwater or improper waste disposal can accelerate the erosion process and trigger sinkholes.
- Natural processes: Heavy rainfall, fluctuations in groundwater levels, and earthquakes can increase the risk of sinkhole formation.
- Soil composition: Areas with loose soil or unconsolidated rock are more susceptible to sinkholes.
- Where are sinkholes most common?
Sinkholes can occur anywhere globally, but they are more frequent in regions with underlying soluble bedrock, particularly limestone. Florida, for example, is notorious for sinkholes due to its extensive limestone geology.
- What are the warning signs of a sinkhole?
While predicting sinkholes with certainty is challenging, some warning signs can indicate potential trouble:
- Cracks in the ground: New or widening cracks in your foundation, driveway, or yard could signal movement beneath the surface.
- Uneven floors: Doors or windows sticking shut or floors tilting unevenly might suggest ground subsidence.
- Pooling water: If water starts pooling in unexpected areas or drains slowly, it could be due to a developing sinkhole.
- Disappearing vegetation: Sudden changes in vegetation growth or trees tilting could be a red flag.
- What should I do if I suspect a sinkhole?
If you suspect a sinkhole on your property, it’s crucial to take immediate action:
- Evacuate the area: If the sinkhole appears large or is actively growing, evacuate the area immediately for safety reasons.
- Contact authorities: Inform local authorities and building inspectors to assess the situation and recommend further steps.
- Consult a professional: Seek advice from a qualified geologist or engineer to evaluate the sinkhole and suggest repair solutions.
- Can sinkholes be repaired?
Sinkholes can be repaired, but the approach depends on the size, depth, and underlying cause. Techniques may involve filling the void with compacted soil, grouting (injecting material to stabilize the ground), or structural reinforcement.
- Are sinkholes covered by insurance?
Standard homeowner’s insurance policies typically don’t cover sinkhole damage. However, some insurers offer optional sinkhole coverage as an add-on. It’s wise to check with your insurance provider to understand your specific policy details.
- How can I prevent sinkholes?
Completely preventing sinkholes might not be possible, but some measures can help reduce the risk:
- Proper drainage: Ensure proper drainage around your foundation to prevent water from accumulating and eroding the soil.
- Limit water usage: Be mindful of water consumption, especially in drought-prone areas. Excessive groundwater withdrawal can contribute to sinkhole formation.
- Maintain septic systems: Regularly maintain septic systems to prevent leaks that could erode the underlying rock.
By understanding the causes and warning signs of sinkholes, you can be more prepared and take necessary actions to ensure your safety.
