Wednesday, November 08, 2023

Geology of the National Parks in Pictures - Carlsbad Caverns National Park

My next post about the Geology of the National Parks Through Pictures is from when I had lived in Texas during the early 2000's. 

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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This is another park that we had visited a long time ago (2003) and I don't have the most geologically themed photos as compared to some of the newer parks that we have visited however the geology is obvious at this park.

Our standard entrance photo shot, even way back then. 


View of the surrounding grounds from near the cave entrance. The modern environment sort of mimics the ancient environment in which the limestone was initially formed. The cave system itself was formed mostly within a formation known as the Capitan Limestone. The Capitan Limestone formed back in the Permian (~276 million years ago) as a reef along the edge of the Delaware Basin, which contained the Delaware Sea, to the east. 

Map of the Delaware Basin. Carlsbad Caverns are "CB" on the map. Image courtesy of Stafford et el., 2009

Following deposition of the Permian Reef, the area was eventually uplifted into the Guadalupe Mountains starting 80 million years ago and accelerating 20-30 million years ago as faulting exposed the once buried reef eventually forming the mountains as we see them today. 


While the dissolution of the caverns started prior to the uplifting of the Guadalupe Mountains, it was the faulting and uplift that prompted the major episodes of cave formation. 

Carlsbad Caverns postcard depicting a map of the caves. Image courtesy of Visit Carlsbad. 

Cave systems are typically formed by the slow dissolution of limestone by a weak carbonic acid. The calcium carbonate (CaCO3) that forms the limestone reacts with the weak acid (H2CO3) that forms when rain water reacts with carbon dioxide. This acid will then slowly dissolve the limestone as rain water percolates through the limestone along cracks and fissures working it's way to the underground water table. 


This is somewhat different than what happened at Carlsbad Caverns. Here a "very aggressive sulfuric acid bath" played a prominent role in cave formation, dissolving the limestone from the water table upwards. The hydrogen sulfide was the result of the regional petroleum reserves that started leaking into the area an estimated 12 million years ago. These sulfuric acid baths are what created the enormous caverns that are a hallmark of the Carlsbad Cavern system.


The natural entrance to the caves then formed once the sulfuric acid baths had retreated ~one million years ago and erosion and gravity force the the ground surface to start to collapse in. At this point "normal" cave development took place with the formation of typical speleothems occurring 

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