The Underground Splendor of Carlsbad Caverns

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The Underground Splendor of Carlsbad Caverns

Total darkness and absolute silence. That is what we encountered deep within the grottoes of Carlsbad Caverns National Park in New Mexico, U.S.A. Upon entering the caverns, we wondered: ‘How did these caves form? How extensive are they? What unusual features lie hidden within them? Are they safe to explore?’

BEFORE touring the caverns, our small group enjoyed camping and hiking in the Guadalupe Mountains National Park in southwest Texas. During our ascent of Guadalupe Peak, the highest point in Texas at 8,749 feet [2,666 meters], we noticed a number of fossils lacing the rocks along the trail. According to geologists, these fossils provide a clue to the origins of Carlsbad Caverns. How so?

Long ago, it seems, algae, sponges, and mollusks thrived here. The whole region was a warm inland sea. Coral, the mainstay of modern reefs, was relatively rare. Some of the more exotic marine life included the now extinct trilobites and ammonoids. Many of the ammonoids lived within large, coiled chambered shells resembling those of the present-day nautilus. We were thrilled to see one of those shells embedded in the rock along the trail!

Apparently, limestone reefs developed as fossil remains of sea life and other particles piled up and cemented together. Because the sea floor sank, the reef complex thickened to more than 1,500 feet [500 meters]. Eventually the sea retreated, and the reefs became deeply buried by sediments. Much later, the land rose, the sediments eroded, and the reefs emerged as mountains. How, though, was this upheaval instrumental in forming Carlsbad Caverns?

Gas, Water, Air, and Acid

As rainwater passes through air and soil, it becomes mildly charged with carbonic acid. This weak acid is apparently responsible for forming most of the world’s limestone caves. However, according to geologist Carol Hill, a much stronger acid hollowed out the caverns of the Guadalupe Mountains.

Hill suggests that sulfur-rich gas formed in oil reservoirs in rocks below the limestone reefs. When the rock mass began to rise, the gas infiltrated the reefs and reacted with air and fresh, oxygenated underground water to form sulfuric acid. This strong acid was able to dissolve large amounts of the limestone rock.

As the mountains rose and the water table dropped, cavern etching progressively deepened. In Carlsbad Caverns, spacious voids and widened fractures interconnected, forming a huge labyrinth. Some 23 miles [37 kilometers] of passages have been mapped here. But they are not the only underground chambers in these mountains. Hundreds more exist. The largest known is Lechuguilla Cave, which has more than 100 miles [160 kilometers] of documented passages!

Cave Decorations

Our first entry into Carlsbad Caverns took us 750 feet [225 m] down an elevator shaft, where we arrived near the Big Room. This huge opening stretches across 14 acres [6 ha]. In places, its ceiling looms more than a hundred feet [30 m] above the floor. But what caught our eye was the wide array of natural cave decorations at every turn, illuminated by hidden lights.

These decorations grow wherever water entering the caves evaporates, causing the lime within it to be deposited. Where water has dripped continually from the same spots on a cave ceiling, thin hollow tubes have grown downward for as much as several feet. These soda straws, as they are called, may eventually become plugged and develop into iciclelike stalactites. Also, hanging below some sloping ceilings, wavy “draperies” enhance the theaterlike appearance of some cavern rooms.

Where the water drips to the floor, pillars may form and grow upward. These stalagmites may eventually connect to the ceiling, perhaps joining a stalactite to form a column. Some of the stalagmites in the Hall of Giants have grown to heights of more than 60 feet [18 m]! If dripping water falls into small hollows, tiny rock fragments can become evenly coated with smooth limestone, resulting in lustrous cave pearls. Even more exotic decorations have developed in some cases. These include delicate clusters of needle-sharp crystals as well as twisted, wormlike tubes known as helictites, which grow in ever-changing directions.

Gazing up at the many immense stalactites, we wondered if there was any danger that they would fall. Our guide reassured us that these cave decorations rarely fall. We hoped that this would hold true during our visit!

The Cave Environment

After enjoying a meal above ground, we descended into the caverns through their natural entrance—a gaping cavity. Rock art drawn by early Native Americans decorates the wall of the opening.

As we entered, we detected the odor of bat guano. We learned that beginning nearly a century ago, the guano was mined for fertilizer. Later, a bucket-and-cable system that was used to remove the guano became the first elevator to take tourists into and out of the caverns. The guano is found in a side passage known as the Bat Cave—the summer home of a million bats. At dusk they soar out of the cave entrance by the thousands.

The park rangers explained to us that the caverns are extremely delicate. Human visitors entering the caves can easily damage and pollute them. For example, just touching the cave decorations can leave oils on their surfaces, preventing continued growth and causing discoloration. Thus, we stayed on the designated trails and avoided touching the cave formations.

As we departed from this hidden scenic wonder, we contemplated returning to see more of the caves. We would like to see the flight of the bats—they have been enjoying the caves a lot longer than human visitors. It is the humans, though, who leave those caves feeling a lingering sense of awe.—Contributed.

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Above: Chandelier stalactites

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Below: Touring the Big Room

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AWAKE!