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What is karst?: Underground formations could tell us why we're here

Adrian Hedden
Carlsbad Current-Argus
A karst-formed sinkhole that funnels water into Eddy County's underground aquifers.

It covers a quarter of the United States, and almost as much of the entire world.

It results in the creation of most caves visited each year by millions of tourists around the globe, including the Carlsbad Caverns National Park.

If it wasn’t for this underground geological phenomenon Carlsbad wouldn’t even exist.

It is responsible for the entire city’s water supply and aquifers.

But what is karst?

The name comes from a region formerly called Kars in what is now Slovenia.

But karst is predominantly identified as a landscape.

It’s not a rock or specific feature.

Karst landscapes form from dissolved bedrock comprised of mostly limestone, and occasionally gypsum, but always soluble rock.  

That rock is eaten away by slightly acidic water, fueled by carbon dioxide in the Earth’s atmosphere and in the soil when rain falls to the ground, creating a weak carbonic acid.

The acid is not dangerous to humans, it exists in the ground we interact with every day.

Limestone fractures are eroded by water to form karst formations at a site in Greece.

Through thousands of years the limestone is slowly eroded — about one inch for every thousand years — forming complex networks of caves and underground passages.

When the water reaches bedrock, it finds cracks in the land, dissolving the earth and enlarging the openings.  

From there, two types of sinkholes can form.

A collapse sinkhole can form as a cavity appears below the earth and the top layer of rock falls in.

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This can cause problems for above-ground activity, such as highways and other types infrastructure.

The other kind of karst sinkhole can bring the most life-sustaining resource bubbling to the surface.

When a solution sinkhole is created, the limestone is eroded from the surface downward into the ground, forming a bowl and creating aquifers where water gathers in the subsequent cavity.

Why do we care?

While many ancient cultures throughout time have revered caves as spiritually significant and important to mythology, the modern-day importance of karst can be summed up in one word.


Karst-formed aquifers and caves that filter and contain underground water supplies are highly sensitive to contamination.

Read:Local leaders take to the sky to witness contrast between nature and extraction

This is because of the complexity and number of passages, which can make it difficult and almost impossible, to find the source of contamination and stop it from spreading.

George Veni, president of International Union of Speleology and executive director of National Cave and Karst Research Institute in Carlsbad, said public and industry leaders should be aware of the locations and sensitivities of karst formations ahead of development, to avoid ruining water supplies.

Understanding the formations, sometimes miles underground, can also help communities plan for the future and know exactly how much water will be available in the decades to come.

Locally, that means being able to understand where the water supplied by the Capitan Aquifer comes from – and how much is left.

Director of the National Cave and Karst Institute George Veni was recently chosen to serve as president of the International Union of Speleology.

“I’m concerned about our understanding of the Capitan,” said Veni.

“I see the potential for uncertainty as to how much water we actually have available in this region. I’m not saying there is a problem, but I’m not saying there isn’t.”

The potential problem centers on water security. In a desert region, water is scarce and becoming scarcer.

A 2005 report from the New Mexico Environment department predicts rainfall in the state will decrease rapidly throughout the rest of the century.

Rain fuels the Capitan aquifer via a karst network, and could easily dry up without enough rain.

“We need to understand what is happening,” Veni said. “Can we be sustained? Maybe we need to think about our business models and change them gradually to make them sustainable in dryer areas.”

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The nature of karst makes the water supply highly vulnerable to contaminants.

Pollutants from industrial activities such as oil drilling can leach into the karst, and can be carried up to three miles in a single day.

Rather than work to stop the contamination from spreading, Veni said contamination needs to be prevented in the first place.

This means greater regulations for activities near karstic regions, and higher scrutiny when approving oil wells.

“If we’re going to drill into a karst aquifer, we need to understand how quickly contamination can occur,” Veni said. “We have to understand that distance doesn’t really matter much. The most important thing is to prevent contamination at all.”

He said many answers remain tucked into the mysterious underground formations.

But none of them will ever make it to the surface if karst is not respected, understood and preserved.

“Sixty years ago we just learned to spell DNA,” Veni said. “What don’t we know today that we will in 60 more years from caves? I don’t want to lose future knowledge because of any present-day shortsightedness.”

Longfellow's Bathtub is the largest and deepest cave pool along the Big Room trail.

The reason we are here

In the case of Carlsbad, karst aquifers caused underground springs to form along and underneath the Pecos River, supplying the southeast corner of New Mexico with the drinking water needed to sustain a community.

“The reason we are here in Carlsbad is karst,” Veni said. 

Veni said most people go about their day on the surface of Carlsbad, unaware of the essential role karst plays in their lives.

“It’s not anything unusual,” Veni said of the formations that can span hundreds of surface acres. “It’s just that people are unaware. Most of the action is occurring underground.”

Most of the karst formations in the United States are east of the Mississippi River, Veni said, but there are pockets in the west.

He said many karst features in the country might be too small for inclusion in most mapping, but NCKRI is hoping to change that.

The institute is part of an international project based in Germany to remap all the karst in the world.

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The four-year project, including a team of international research groups, aims to include karstic areas that are more fragmented compared to the enormous swaths in Russia and China.

Veni said the project will look to include smaller karstic areas with bigger social importance.

Before, mapping activity would only include areas that were at least 65 percent karst, while the state of New Mexico is about 20 percent.

But the smaller karst regions in the state pose more importance to people than vast expanses in the Siberian wilderness where few people reside.

“The amount any country has is luck,” Veni said. “It’s based on where the borders happen to be.”

Other countries are taking note of the importance of karst and its preservation, he said.

In Brazil, although the country is only about five percent karst, miners or any developers in karst areas must adhere to heightened government regulations.

“They recognize the importance and significance,” Veni said. “Here it’s mostly rolled into ground water protection.”
