Bear Lake Limestone

Bear Lake Limestone: Pale Blue Bear Lake from the Shore, Courtesy & Copyright Mary Heers, Photographer
Pale Blue Bear Lake from the Shore
Courtesy & Copyright Mary Heers, Photographer

Blue Sky Reflected on the Water of Bear Lake, Courtesy & Copyright Mary Heers, Photographer Blue Sky Reflected on the Water of Bear Lake
Courtesy & Copyright Mary Heers, Photographer

Stalagmites in Minnetonka Cave, St Charles Canyon, West of Bear Lake, Courtesy & Copyright Mary Heers, Photographer Stalagmites in Minnetonka Cave, St Charles Canyon, West of Bear Lake
Courtesy & Copyright Mary Heers, Photographer

Soda Straw Stalactites in Minnetonka Cave, St Charles Canyon, West of Bear Lake, Courtesy & Copyright Mary Heers, Photographer Soda Straw Stalactites in Minnetonka Cave, St Charles Canyon, West of Bear Lake
Courtesy & Copyright Mary Heers, Photographer

Small Ribbon  Stalactites in Minnetonka Cave, St Charles Canyon, West of Bear Lake, Courtesy & Copyright Mary Heers, Photographer Small Ribbon Stalactites in Minnetonka Cave, St Charles Canyon, West of Bear Lake
Courtesy & Copyright Mary Heers, Photographer

Stalagmite in Minnetonka Cave, St Charles Canyon, West of Bear Lake, Courtesy & Copyright Mary Heers, Photographer Stalagmite in Minnetonka Cave, St Charles Canyon, West of Bear Lake
Courtesy & Copyright Mary Heers, Photographer

If you stop at the overlook above Bear Lake on a sunny summer day, you may be as surprised as I was to find out that the gray limestone rocks in Logan Canyon are responsible for the brilliant blue color of the lake. Among the wealth of information displayed at the overlook is the fact that as rainwater and melting snow seeps down through the limestone, it picks up tiny bits of calcium. This calcium in the lake water acts as “millions of microscopic mirrors” that reflect the exact color of the blue sky.

Once I started thinking about water seeping through this limestone, I signed up to take a tour of the Minnetonka Caves located above St Charles towards the northern side of the lake. Millions of years ago, water began to seep into small fissures in the rock, widening into larger cracks and puddling into low spots. When the water table dropped, the water drained away, leaving large crevices and 9 open rooms behind.

The cave was discovered in 1906 by Edward Arnell, who was out hunting and shot a grouse that fell just over a nearby ledge. He scrambled down to retrieve the bird, and then he felt it: cold air. Pushing aside some rocks he found the hole in the hillside – just large enough for a man to crawl through.

He found a bear skeleton near the entrance, but no sign that humans had ever been inside the cave before.

In 1939 the WPA went to work enlarging the entrance. They chiseled 444 steps into the rock and paved a rough path between the rooms.

Today the cave is managed by the Montpelier Ranger Station, who lead tours into the cave in the summer months. When my turn came, I slipped on my hoodie, grabbed the ice cold railing, and started down the slippery steps with my group. A generator was keeping the path dimly lit while spotlighting some of the drip formations. I was expecting stalactites and stalagmites, but I was delighted to also see sheets of dripping water frozen in time and looking very much like drapes. Hollow tubes called “soda straws” hung from the ceiling.

About half a mile into the cave our guide stopped us and turned us around. The rest of the cave, he said, was reserved for the five species of bats that spend the winter here. The cave stays at a cool 40 degrees year round – a perfect temperature for hibernating bats who will lower their temperature to near freezing, slow their heartbeat from 200 to 10 beats a minute, and only take a breath every few minutes.

I guess I’ve always envied hibernating mammals like bats and bears who go to sleep fat, doze through the winter, and wake up thin in the spring.

Before we started back up the 444 steps, our guide had one more lesson for us. He turned off the lights to allow us to experience a few moments of utter darkness.

Just as the lights came back on, a drip of cold water fell from the cave ceiling and landed on me. I felt like I’d been kissed.

This is Mary Heers and I’m Wild About Utah.

Credits:

Photos:
Featured Audio: Courtesy & Copyright Patrick Kelly, Bird Sounds Courtesy & Copyright Kevin Colver and Water at end Courtesy FreeSound.org, Sclolex, contributor
Text: Mary Heers, https://cca.usu.edu/files/awards/art-and-mary-heers-citation.pdf
Additional Reading: Lyle Bingham, https://bridgerlandaudubon.org/

Additional Reading

Wild About Utah, Mary Heers’ Postings

Boling, Josh, Karst Topography, Wild About Utah, November 23, 2o2o, https://wildaboututah.org/karst-topography/

“It is a karst limestone cave, formed from ground water flowing through limestone and carving sink-holes and underground waterways.”
Minnetonka Cave, USDA Forest Service, US Department of the Interior, https://www.fs.usda.gov/recarea/ctnf/recarea/?recid=70736

Minnetonka Cave Brochure, USDA Forest Service, US Department of the Interior, 23.308.415.04/04, https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev3_015684.pdf

History of Minnetonka Cave, The Herald Journal, August 6, 2020, https://www.hjnews.com/bear_laker/history-of-minnetonka-cave/article_950c5030-d82d-11ea-9bf1-47556f110eed.html

Davis, Jim and Milligan, Mark, Why is Bear Lake so Blue? and other commonly asked questions, Public Information Series 96, Utah Geological Survey, Department of Natural Resources, 2011, https://ugspub.nr.utah.gov/publications/public_information/pi-96.pdf

Karst Topography

Karst Topography: Entrance to a Karst Cave Courtesy & © Josh Boling
Entrance to a Karst Cave
Courtesy & © Josh Boling
Rivers run beneath these hills, carving winding caverns through ancient stone, plumbing a subterranean watershed—a second topography, ever changing. What little we’ve seen must lead further in, places mythology might only describe.

Karst topography’ refers to landscapes cleaved apart by the leaching of water through a soluble bedrock layer comprised of carbonate-rich rocks like the limestone and dolomite found throughout Utah’s mountains or the evaporate-type gypsum and rock salt layers found in Utah’s redrock country. Over time, this erosion by surface and groundwater creates pinnacles, rippling fissures, gaping sinkholes, or springs on the surface—deep caverns, plummeting vertical shafts, and winding tunnels through which entire rivers can flow below.

We floated one such river once, in complete darkness, guided only by a subtle current and the voice of our local guide. He said he was of Mayan descent, so we listened closely when he relayed stories of Chaac, the Mayan god of rain responsible for the generous flow of water through the caverns we explored. Indeed, it is within these same caverns that he dwells, we were told. Further north, in Mexico and the desert southwest, it’s Tlaloc, the goggle-eyed Aztecan deity that controls the rain. He, too, is supposed to reside within the body of the earth.

Karst Cave Courtesy & © Josh Boling
Karst Cave
Courtesy & © Josh Boling
There’s no mythology I’m aware of for my little corner of the globe. So, scientists and explorers alike descend into the karstic caves of northern Utah to see what they might learn. “Utah is unique,” one such explorer told me, “with some of the most difficult caves that exist in the world, then some of the most spectacular, and some of the most benign.” Intrigued, I set out to see what I could find in my own back yard. Ribs of bleached limestone called karrens spread across a plateau like a washboard road, sinkholes that occupy the better part of an entire meadow, blind valleys sunken into a void in the bedrock, innumerable unnamed springs, and a small, non-descript cavity in the crust—the thing I had really been looking for this whole time.

Main Drain is Utah’s deepest and the nation’s 11th-deepest cave. It’s also wildly difficult and dangerous to navigate, yet absolutely critical to explore for the sake of furthering scientific understanding. I talked to Larry Spangler of the US Geological Survey in Salt Lake City about the significance of karst landscapes like Main Drain. “The caves that are developed in these terrains,” Spangler says, “are…valuable sources of information in regard to changes in climate and landscape evolution over time.” The chemistries of these caves are unique to their environment, and analysis of mineral deposits within the caves can provide insights into how average surface temperatures have changed over time and how wet or dry the landscape above was in any given period. Karst caves can reveal climate data for specific locales that may help us predict how a warming planet might affect our local ecosystems.

The water that flows through Main Drain and other cave systems like it in the form of snowmelt and subterranean streams carves its way vertically and horizontally through layers of bedrock hundreds of millions of years old—providing researchers a literal inside look at the formation of mountains. And as a map of these subterranean watersheds begins to come together, we gain a better understanding of the hydrology of an area and its effects on water quality.

When I spoke to Spangler, he wanted to make it very clear just how sensitive these karst landscapes are to surface activities, for the health of ecosystems and the integrity of watersheds, of course, but also for the health of human communities. The US Geological Survey estimates that as much as a quarter of the world’s population depends on karst landscapes for their water supply. The city of Logan, where my family and I live, sources its water from one of the larger karst springs in the area. The people are drinking straight from the mountain.

Rivers run beneath these hills, and through us as well.

I’m Josh Boling, and I’m Wild About Utah!
 
Credits:
Photos: Courtesy & Copyright Josh Boling, Photographer
Sound: Courtesy & Copyright Josh Boling
Text: Josh Boling, Edith Bowen Laboratory School, Utah State University https://edithbowen.usu.edu/
Additional Reading Links: Josh Boling

Sources & Additional Reading

Author’s note: Caves and other karst features are inherently dangerous. You should never enter a cave or other karst feature without the appropriate training, gear, and an experienced person(s) to accompany you.

Shurtz, David K & Shurtz, Ryan K, The Discovery, Exploration of, and Sufferings withing Utah’s Main Drain Cave, Utah Grottos, April 2005 https://www.jonjasper.com/TonyGrove/MainDrainCave-NSSApril2005.pdf

Haydock, Adam, Cave Dive Operations in Main Drain Cave, Utah, https://www.even-further.com/dive-expedition-in-main-drain-utah

Caving Main Drain Cave, Logan Canyon, Utah, Outdoor Activities, The Dye Clan, August 31, 2013, https://dyeclan.com/outdooractivities/caving/?id=334

Main Drain Cave, Utah Caving, February 14, 2014, https://utahcaving.wordpress.com/2014/02/14/main-drain-cave/

Karst Topography Paper Model (Learning Activity, Grade Level: 9-12), National Park Service, US Department of the Interior, https://www.nps.gov/subjects/caves/karst-topography-model.htm
Karst Topography Paper Model Background
Soto, Limaris R.(modified by), After: Alpha, Tau Rho, Galloway, John P, and Tinsley III, John C., Karst (U.S. Geological Survey Open-file Report 97-536-A), Topography Paper Model, U.S. Department of Interior, U.S. Geological Survey, National Park Service, https://www.nps.gov/subjects/caves/upload/Karst-Topography-Model-_Written-Section_508c.pdf (formerly: https://www.nps.gov/subjects/caves/upload/Final-Karst-Topography-Model-_Written-Section_5-14-2014.pdf)

Weary, David J. and Doctor, Daniel H., Karst in the United States: A Digital Map Compilation and Database, Open-File Report 2014–1156, U.S. Geological Survey(USGS), https://pubs.usgs.gov/of/2014/1156/pdf/of2014-1156.pdf

Lawrence, Lawrence E., Delineation of Recharge Areas for Karst Springs in Logan Canyon, Bear River Range, Northern Utah, U.S. Geological Survey/The Pennsylvania State University, https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.543.5904&rep=rep1&type=pdf

Francis, George Gregory, Stratigraphy and Environmental Analysis of the Swan Peak Formation and Eureka Quartzite, Northern Utah, (1972). All Graduate Theses and Dissertations. 1684 https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2683&context=etd

Morgan, Susan K., Geologic Tours of Northern Utah, Miscellaneous Publications, 92-1, Utah Geological Survey, Adivision of Utah Department of Natural Resources, (1992), https://ugspub.nr.utah.gov/publications/misc_pubs/mp-92-1.pdf

Connecting Caves, Karst Landscapes and Climate Around the World, Circle of Blue, January 18, 2010, https://www.circleofblue.org/2010/world/connecting-caves-karst-landscapes-and-climate-around-the-world/

Bahr, Kirsten, “Structural and Lithological Influences on the Tony Grove Alpine Karst System, Bear River Range, North Central Utah” (2016). All Graduate Theses and Dissertations. 5015. https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=6053&context=etd