Skip to content
Know.itKnow.it
Create an animated lesson
On request

This article is free to read. Creating a lesson uses your daily or stored credits; review the language and settings before starting.

How does a sinkhole form?

ScienceLesson on requestFree to read

Quick answer

A sinkhole forms when underground rock, such as limestone, is dissolved by acidic water, creating hidden cavities. When the roof of a cavity becomes too weak to support the surface, the ground collapses or gradually subsides, leaving a depression. Human activities like pumping groundwater can speed up this process.

A sinkhole forms when underground rock or sediment is dissolved or washed away, creating a void that can no longer support the ground above. The surface then collapses or subsides into the cavity, often suddenly.

Step by step

  1. Rainwater absorbs carbon dioxide from the air and soil, becoming a weak acid.
  2. This acidic water seeps through cracks and joints in soluble bedrock like limestone.
  3. Over time, the water dissolves the rock, enlarging cracks into underground cavities and channels.
  4. As the cavities grow, the overlying rock and soil become unsupported.
  5. Eventually, the surface collapses suddenly or subsides gradually into the void.
  6. Human activities such as groundwater pumping or leaking pipes can accelerate the collapse.

Key things to understand

  1. Sinkholes typically occur in areas underlain by soluble rocks like limestone, gypsum, or salt.
  2. Rainwater absorbs carbon dioxide from air and soil, forming weak carbonic acid that dissolves these rocks over time.
  3. This dissolution creates networks of underground cavities and channels, a process called karstification.
  4. When the roof of a cavity becomes too thin to support the overlying weight, it collapses.
  5. Human activities such as pumping groundwater, leaking pipes, or construction can accelerate sinkhole formation.

Labelled diagram

  1. Soluble bedrock

    Layers of limestone, gypsum, or salt lie beneath the surface.

  2. Acidic water

    Rainwater mixed with carbon dioxide seeps down and dissolves the rock.

  3. Cavity forms

    Dissolution creates underground voids and channels over many years.

  4. Roof thins

    The cavity grows, leaving only a thin layer of rock and soil above.

  5. Collapse

    The surface gives way, creating a visible sinkhole.

How a sinkhole forms

Real-world examples

  • The Winter Park sinkhole in Florida, USA, opened in 1981 and swallowed a house, cars, and part of a swimming pool.
  • The Dead Sea sinkholes along its shores have formed due to the sea's receding water level, causing numerous collapses.
  • In 2010, a massive sinkhole in Guatemala City swallowed a three-story building, likely triggered by sewer leaks and heavy rain.
  • The Yucatán Peninsula in Mexico is dotted with cenotes, natural sinkholes that expose groundwater and were sacred to the Maya.

Common mistake

✗ Myth: Sinkholes are always caused by human activity.

✓ Fact: While human activities like groundwater pumping and leaking pipes can trigger sinkholes, most are natural processes that occur in soluble bedrock terrains over long periods. Human actions often accelerate but do not solely cause them.

People also ask

What causes sinkholes?
Sinkholes are caused by the natural dissolution of soluble bedrock like limestone by acidic groundwater, which creates underground cavities. When the roof of a cavity collapses, a sinkhole forms. Human activities such as pumping groundwater, leaking pipes, or construction can also trigger or accelerate sinkhole formation.
Where do sinkholes occur?
Sinkholes occur worldwide but are most common in regions underlain by soluble rocks such as limestone, gypsum, and salt. Notable areas include Florida, Texas, and Kentucky in the US; the Yucatán Peninsula in Mexico; and parts of China, Italy, and the Middle East. These regions are often characterized by karst topography.
How to tell if a sinkhole is forming?
Warning signs of a forming sinkhole include small circular depressions in the ground, cracks in foundations or roads, tilted trees or fence posts, and muddy water in nearby wells. If you notice these signs, it's best to avoid the area and contact local authorities or a geologist.
Can sinkholes be predicted?
Sinkholes are difficult to predict precisely, but geologists can identify high-risk areas by mapping soluble bedrock, monitoring groundwater levels, and using ground-penetrating radar to detect voids. Early warning signs include small cracks, depressions, or tilted trees.
Are sinkholes dangerous?
Yes, sinkholes can be dangerous because they often collapse suddenly, swallowing cars, roads, and sometimes buildings. They can also cause structural damage and disrupt utilities. However, most sinkholes are small and occur in rural areas, posing limited risk to people.
What is the difference between a sinkhole and a pothole?
A pothole is a shallow depression in a road surface caused by wear and water, while a sinkhole is a natural depression or hole in the ground formed by the dissolution of bedrock or collapse of a cave. Sinkholes can be much larger and deeper than potholes.
Can sinkholes be fixed?
Yes, sinkholes can be repaired by filling them with concrete, grout, or soil, but the underlying cause must be addressed to prevent recurrence. In some cases, engineers inject grout to stabilize the ground. Proper drainage and groundwater management are also important.

Part of the guide: Water & Weather Phenomena →