13 of the World’s Most Astonishing Sinkholes
Explore the extraordinary beauty, danger, and rarity of the planet's largest and most mesmerizing sinkholes.
Sinkholes capture the human imagination with their sudden appearance, overwhelming scale, and mysterious depths. Some are vast geological wonders shaping entire landscapes, others are ominous reminders of the power and unpredictability of nature beneath our feet. This article explores thirteen of the most extraordinary sinkholes and dolines on Earth, with insights into their formation, location, and unique stories.
What Is a Sinkhole?
A sinkhole is a depression or hole in the ground caused by the collapse of a surface layer. While some may measure just a few feet across, others open up as vast craters, exposing dramatic underground voids. Most natural sinkholes form in regions of karst landscapes, where slightly acidic rainwater slowly dissolves soluble bedrock—such as limestone, gypsum, or salt—over thousands or millions of years. As underground cavities grow, the land above may eventually cave in, forming vertical shafts or gentle depressions known as dolines.
Sinkholes are found all over the world, ranging from tiny pits in fields to some of the planet’s largest and most impressive geological wonders. The following list showcases thirteen places where Earth’s crust has surrendered to the forces below in magnificent fashion.
1. Xiaozhai Tiankeng, China
Xiaozhai Tiankeng, often called the “Heavenly Pit,” is the world’s largest sinkhole by volume. Located in Fengjie County, Chongqing, China, this colossal collapse measures around 662 meters deep (2,172 feet), 511 meters wide (1,677 feet), and up to 626 meters long (2,054 feet).
- Formation: Created by the collapse of a giant cave, with water from the Qingkou River steadily eroding the underlying limestone.
- Features: Steep, nearly vertical cliffs; lush subtropical vegetation thriving at the bottom owing to its unique microclimate; home to rare plants and animals.
- Notable: The Tiankeng is a magnet for geologists, cavers, and adventure tourists.
2. Great Blue Hole, Belize
The Great Blue Hole is one of the world’s most recognizable marine sinkholes. Located off the coast of Belize, near Lighthouse Reef, this underwater chasm measures about 318 meters across (1,043 feet) and 124 meters deep (407 feet).
- Formation: Formed during the last Ice Age, it was once a limestone cave above sea level before rising waters inundated and collapsed its roof.
- Features: Perfectly circular, deep blue coloring contrasts with turquoise waters; rich marine life with stalactites and underwater caves.
- Notable: Declared a UNESCO World Heritage Site and one of Jacques Cousteau’s top scuba diving spots.
3. Dean’s Blue Hole, Bahamas
Found on Long Island, Dean’s Blue Hole is the world’s deepest known seawater blue hole with an entrance below sea level. This vertical cavern plunges to a depth of about 202 meters (663 feet).
- Features: Gorgeous setting surrounded by white sandy beaches and limestone cliffs; a magnet for divers and free-diving record attempts.
- Notable: Because of its depth and clear waters, it remains a hotspot for underwater exploration and scientific research.
4. Sótano de las Golondrinas (Cave of Swallows), Mexico
Nestled in Mexico’s San Luis Potosí state, the Cave of Swallows is among the world’s deepest freefall pit caves. The entrance is 49 by 62 meters (161 by 203 feet), dropping straight down 370 meters (1,214 feet) from the opening to the bottom.
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- Formation: Shaped by water dissolving limestone, then carving out a staggeringly deep, vertical shaft.
- Features: Frequented by vast flocks of birds—swifts and parakeets—which glide into the pit at dusk and dawn.
- Notable: Renowned for base jumping and vertical caving.
5. Bimmah Sinkhole, Oman
The Bimmah Sinkhole is a picturesque limestone crater filled with turquoise water, located between the coastal city of Muscat and the town of Sur, Oman. It measures about 40 meters across (131 feet) and 20 meters deep (65 feet).
- Features: Popular swimming destination; easy access via a public park.
- Notable: Local legends once attributed its formation to a meteorite impact, but geologists confirm it was formed by natural dissolution and collapse.
6. Big Hole (Kimberley Mine), South Africa
The Big Hole, situated in Kimberley, South Africa, is not a natural sinkhole but an immense hand-dug pit created by diamond mining between 1871 and 1914. Over 50,000 miners excavated nearly 14.5 million tons of earth, resulting in a hole over 215 meters deep (705 feet) and 463 meters wide (1,519 feet).
- Features: Now a historical landmark; filled partially with turquoise water.
- Notable: One of the largest excavations ever made by hand, illustrating the power of human-driven landscape change.
7. Qattara Depression, Egypt
The Qattara Depression in Egypt is the second lowest point in Africa and the largest natural sinkhole by surface area. Spanning over 19,000 square kilometers (7,300 square miles), the Qattara Depression drops to -133 meters (-436 feet) below sea level at its lowest point.
- Features: A vast, salty, uninhabitable expanse punctuated by quicksand, salt flats, and wind-eroded formations.
- Notable: Too inhospitable for settlement, it demonstrates how geological phenomena can shape entire regions over millennia.
8. Great Cenote, Mexico
The limestone-rich Yucatán Peninsula boasts thousands of cenotes—natural sinkholes once sacred to the Maya. One of the most famous, the Great Cenote near Tulum, is celebrated for its crystal-clear waters and extensive cave system.
- Features: Popular for snorkeling and cave diving; abundant aquatic life; source of fresh water for the ancient Maya.
- Notable: A window into the world’s largest underwater river and cave networks, some of which are still being mapped.
9. Red Lake, Croatia
Located near Imotski in Croatia, Red Lake is a massive sinkhole filled with water, measuring approximately 530 meters deep (1,739 feet). Its reddish cliffs are iron oxide-stained, giving the lake its distinct appearance.
- Features: Vertical cliffs plunge directly into deep blue waters; mysterious tunnels and caves are hidden at depth.
- Notable: One of the deepest sinkhole lakes in the world. The depth from the surface of the lake to the deepest explored point is over 530 meters.
10. Guatemala City Sinkhole, Guatemala
Guatemala City, built atop layers of volcanic pumice, has been struck by multiple dramatic sinkhole collapses. In 2007 and again in 2010, massive voids appeared in a populated district, each roughly 20 meters wide (65 feet) and plunging more than 90 meters deep (300 feet).
- Formation: Triggered not just by natural karst erosion but also by leaky sewer and water pipes eroding soft underground sediments.
- Features: Near-perfectly cylindrical; caused destruction of homes and infrastructure.
- Notable: Became global news and a symbol of the risks in rapid urban development over vulnerable substrates.
11. Winter Park Sinkhole, Florida, USA
Florida’s karst terrain makes it a hotspot for sinkholes, but few are as dramatic as the Winter Park Sinkhole of 1981. Overnight, a hole 100 meters wide (330 feet) and 30 meters deep (98 feet) opened up in a residential neighborhood, swallowing homes, cars, and even a swimming pool.
- Features: Rapid, catastrophic collapse; filled in and now serves as an urban lake known as Lake Rose.
- Notable: The story of the collapse garnered national attention and highlighted the unpredictable dangers of living atop soluble limestone bedrock.
12. Devil’s Sinkhole, Texas, USA
Located near Rocksprings, Texas, the Devil’s Sinkhole is a massive vertical pit cave in a remote area. The entrance measures 15 meters across (50 feet) but plunges to a cavern over 106 meters deep (350 feet).
- Features: Famous for nightly flights of thousands of Mexican free-tailed bats emerging from the cave from late spring through early autumn.
- Notable: Accessible only by guided tours and carefully managed to preserve fragile ecosystems.
13. Sarisarinama Sinkholes, Venezuela
The Sarisarinama sinkholes are among the most remote and mysterious in the world, located atop a remote tepui (tabletop mountain) in Venezuela’s Guayana Highlands. There are several major sinkholes, the largest reaching 350 meters across (1,150 feet) and over 314 meters deep (1,030 feet).
- Features: Lush, isolated forests exist at the bottom of each sinkhole, teeming with unique, endemic species.
- Notable: Scientists believe they may be among the oldest dolines in the world, formed by a combination of erosion and collapse.
How Do Sinkholes Form?
While some giant sinkholes are the result of mining or collapse triggered by human activity, most natural sinkholes stem from centuries or millennia of underground erosion:
- Dissolution: Slightly acidic water gradually dissolves soluble rock (e.g., limestone), forming cavities.
- Collapse: When cavities become too large to support the ground above, a sudden collapse may create dramatic holes.
- Dropout: Sediments wash into a cavity, forming a conical depression rather than a gaping chasm.
- Man-made triggers: Leaking pipes, mining, drilling, and poor construction can induce or accelerate sinkhole formation in vulnerable terrain.
Regions most prone to sinkhole formation typically feature abundant karst topography, as found in southern China, the Balkans, Florida, parts of the Middle East, and much of Central America.
Notable Sinkhole Facts
- Sinkholes vary dramatically in size, from less than a meter to hundreds of meters across and deep.
- Many famous lakes, such as Florida’s Lake Eola, began as ancient sinkholes.
- Sinkholes can suddenly swallow buildings, roads, and lakes, or develop gradually over decades.
- More than 20% of the world’s landmass features karst or pseudokarst (volcanic or erosional) landscapes prone to sinks and caves.
- Some sinkholes host isolated ecosystems, with species found nowhere else on earth.
Frequently Asked Questions (FAQs)
Q: What is the difference between a sinkhole and a doline?
A: All dolines are sinkholes, but the term doline is typically used in geological literature for larger or more gradual collapse features in karst terrains, while sinkhole can refer to any ground depression caused by subsurface void collapse, including both rapid and gradual events.
Q: Are all sinkholes dangerous?
A: Not all sinkholes pose an immediate risk. Slow-forming dolines may remain stable for centuries or serve as lakes or tourist sites. However, sudden collapse sinkholes, particularly in populated areas, can be hazardous and unpredictable.
Q: Where are sinkholes most common?
A: Sinkholes are most common in regions with extensive limestone bedrock, such as southern China, the southeastern United States (Florida is especially famous), Central America, the Balkans, and parts of the Middle East and Australia.
Q: How can sinkholes be prevented or managed?
A: While natural sinkholes can’t be prevented, man-made collapse risk can be reduced by carefully managing water flow, avoiding over-extraction of groundwater, maintaining water infrastructure, and regulating development over vulnerable areas. Proper soil compaction and avoiding excessive groundwater depletion are critical in high-risk locations.
Q: Why are sinkholes important to scientists?
A: Sinkholes offer natural laboratories for studying hydrogeology, unique ecosystems, climate history (trapped sediments), and the effects of human activity on landscapes. Some reveal previously unknown species or preserve perfectly isolated biological communities.
Summary Table: The World’s Most Remarkable Sinkholes
| Name | Location | Type | Depth | Width/Diameter |
|---|---|---|---|---|
| Xiaozhai Tiankeng | China | Collapse doline | 662 m | 511 m |
| Great Blue Hole | Belize | Marine sinkhole | 124 m | 318 m |
| Dean’s Blue Hole | Bahamas | Marine sinkhole | 202 m | ~ |
| Cave of Swallows | Mexico | Vertical shaft | 370 m | 49×62 m |
| Bimmah Sinkhole | Oman | Limestone sinkhole | 20 m | 40 m |
| Big Hole | South Africa | Man-made | 215 m | 463 m |
| Qattara Depression | Egypt | Large depression | 133 m | 19,000 km² |
| Great Cenote | Mexico | Karst cenote | Varies | Varies |
| Red Lake | Croatia | Sinkhole lake | 530 m | ~ |
| Guatemala City | Guatemala | Urban collapse | 90+ m | 20 m |
| Winter Park | Florida, USA | Collapse sinkhole | 30 m | 100 m |
| Devil’s Sinkhole | Texas, USA | Vertical pit | 106 m | 15 m |
| Sarisarinama Sinkholes | Venezuela | Collapse doline | 314 m | 350 m |
From lost lakes and turquoise caverns to massive pits swallowing entire neighborhoods, sinkholes serve as nature’s remarkable (and sometimes terrifying) reminders of Earth’s hidden processes. They are vital for understanding geology, groundwater systems, and even the origin of unique ecosystems. Whether you’re a geologist, adventurer, or armchair traveler, the world’s great sinkholes offer lessons and landscapes like nowhere else on the planet.
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