The Many Faces of Limestone
Limestone is a unique character is the rock world. There are only a handful of rocks that can be dissolved in water, and limestone is by far the most common of that group (other members include salt and gypsum). Most limestones are composed of the skeletal remains of deceased marine organisms (a handful are formed by entirely inorganic processes), so their presence generally indicates that an area was home to a warm, shallow sea at some time in the past. Fossils of coral, clams, snails, and other water-loving critters are often abundant in limestone, and in some ways, a chunk of marine limestone IS one gigantic fossil!
The aforementioned critters make their shells out of calcium carbonate, which is soluble in slightly acidic water. Most water on Earth’s surface is slightly acidic (due to interactions with carbon dioxide in our atmosphere) so interesting things can happen when water and limestone interact…especially if you give them lots of time! In particular, groundwater is capable of dissolving huge voids in limestone bedrock over long periods of time, forming features such as sinkholes and caverns.
Limestone is an abundant rock in our neck of the woods, especially in the mountain ranges astride the Utah/Nevada border in the Great Basin. Throughout much of the Paleozoic Era (541 to 252 million years ago), this region was covered by a series of vast, warm, shallows seas, much like the one that now draws millions to the Bahamas every year.
A great place to see limestone in action is the area around Great Basin National Park. Tucked away in extreme east-central Nevada, Great Basin is one of my favorite national parks, far removed from the hoards that descend annually on many of the west’s more well-known attractions. You have to make an effort to get here and at first glance, the Snake Range of Great Basin NP looks pretty much like any other mountain island rising up out of the Basin & Range. Upon closer inspection, it’s actually home to a stunningly diverse array of landscapes: The 2nd highest peak in Nevada (Wheeler Peak at 13,065 feet), some of the world’s oldest trees, and arguably the darkest night skies in the Lower 48 all reside here.
But limestone is ultimately the reason a national park exists in this corner of Nevada. A small portion of the area was originally set aside as a national monument in 1922 to protect Lehman Caves, a stunning cavern eaten into the 500 million year old Pole Canyon Limestone. Only in 1986 was the monument enlarged into a National Park encompassing both the caves and the surrounding mountain landscape.
While small in size, Lehman Caves is exquisitely decorated with a wide variety of speleothems (cave formations). Stalactites, stalagmites, shields, draperies, cave bacon, cave popcorn, soda straws, and helectites surround you at every turn as you wander through the cave. Photos show details not immediately visible to the human eye in the dimly lit cave, revealing an underground world that looks more like a well manicured sci-fi movie set than a natural place sculpted by nothing more than the water, limestone, and time.
Back on the surface, no trip to Great Basin NP is complete without a hike to admire some of the oldest living things on the planet: the Great Basin Bristlecone Pines (Pinus longaeva). Curiously, even these trees have an intimate relationship with the limestone that is so common here. Most of the bristlecone pine groves throughout the Great Basin are found growing on soils derived from limestone or dolomite (a limestone relative). For some reason, the bristlecones seem to prefer this rock type, perhaps because many other species do not, thus minimizing competition. The easily accessible grove on the flanks of Wheeler Peak (pictured below) is perhaps the most notable exception. Here the trees grow not in limestone, but among hard quartzite boulders deposited by old glaciers.
About an hour east of Great Basin, slightly younger (~490 million years) limestone in the House Range forms another unique feature: Notch Peak. At just 9,658 feet, Notch Peak doesn’t measure up in altitude with many other summits in the region. It’s claim to fame is its 2,200 foot sheer northwest face, one of the tallest cliffs in North America. Where exactly it ranks on that list depends on your definition of “cliff,” but there seems to be little debate that it is the tallest limestone cliff on the North American continent. The peak is striking, especially when viewed from the west, where the full magnitude of its 4,000+ foot rise from the Tule Valley below is apparent.
We spent an enjoyable evening camping in the shadow of Notch Peak and had hoped to hike to the summit the next day via Sawtooth Canyon on the east side, but unfortunately car issues derailed that plan.