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Roger Weller, geology instructor

Lava Tubes
by Season Osterfield
Physical Geology
Spring 2013


The Shoshone Indian Ice Caves


     In south central Idaho, about thirty minutes from the city of Twin Falls, there exists a smaller town named Shoshone. Since its establishment, Shoshone, named after the Native American Indian tribe, has been known for being “the only place for hundreds of miles where one could get a cold beer.”[1] This slogan comes from Shoshone's year round ice source, the Shoshone Indian Ice Caves. The Shoshone Indian Ice Caves are located 16 miles north of Shoshone and are just one location in Idaho of ice caves occurring.



The interior and a portion of the wooden bridge within the Shoshone Indian Ice Caves

Image courtesy of TripAdvisor - copyrighted


     The Shoshone Indian Ice Caves are actually a collection of old lava tubes that are among many throughout Idaho. The air currents flowing through the tubes cause the water inside to freeze during the winter and very slowly thaw in the summer (but never completely), only to refreeze again come winter. This is all a direct result of the temperature extremes experienced in the area outside the caves. During the summer, it can get to be well over 100 degrees Fahrenheit and below 20 degrees Fahrenheit in the winter. [2][3][4][5]


     The main ice cave, where tours are run through, varies between 8 to 30 feet in width and has a height of 40 feet in some areas. The cavern itself runs 1,000 feet in length as well. The temperature inside varies at locations from as low as 18 degrees Fahrenheit to as high as 33 degrees Fahrenheit. Despite many attempts by geologists, it is still unknown how thick the ice is at the end of the cave. [2][3][4][5]


     Visitors of the cave walk the length of the lava tube along a wooden bridge with enough space for one adult and a young child to stand side by side somewhat comfortably. Beneath the bridge and all along the cavern floor is a large sheet of slick, smooth ice. The bridge stops at the end of the cave where there is a thick wall of ice.[2]



The interior and a portion of the wooden bridge within the Shoshone Indian Ice Caves

Image courtesy of TripAdvisor - copyrighted


     In the the 1940s, an additional entrance was added to the cave which caused the air currents inside to be altered. As a result of the changed air flow, all of the ice melted. In  the 1950's, the Robinson family acquired the rights to the Shoshone Indian Ice Caves and sealed the additional entrance, restoring the air currents to the original flow. By 1962, the ice had once again returned to the cave. [2]


     Lava tubes are formed in the central portion of a lava flow. Once the lava has been released from the volcano, the outer portions of it begin to freeze in place, creating a hallow tube. Although the outside of the tube is cooled and solid, the inside continues to flow with lava that heads out to the flow front. Once the lava source has been cut off, like the volcano finishing its eruption, the lava flows the rest of the way out of the tube and any remaining inside cools, forming stalagmites and stalagmites. [6]











A collapsed lava tube near the Shoshone Indian Ice Caves

Image courtesy of TripAdvisor - copyrighted



     The lava tubes that make up the Shoshone Indian Ice Caves are the result of eruptions thousands of years ago from the Black Butte Crater shield volcano. The volcano is currently dormant with its last eruption having been 1,500 to 2,000 years ago. However, in July of 1973 and again in July of 1974, a vent on the north-west side of the volcano began spouting out a column of gas, but just as suddenly as it started, it stopped. [7]


     Black Butte Crater is about a 7 mile drive from the Shoshone Indian Ice Caves. The volcano has created an “L” shaped lava flow that is 1.25 miles to 3 miles in width and extends about 37 miles south and west. The Shoshone Indian Ice Caves are included within the volcano's “L” shaped lava flow. [8]


     Prior to the town of Shoshone using the ice caves for ice in the 1880s, the caves were used by the Shoshone Indians as a source of ice and more or less a giant refrigerator. In the late 1800s, when the mining boom was active, miners' payrolls were run back and forth past by stagecoaches along the Big Wood River. Bandits would routinely rob the stagecoaches and then flee to the ice caves where there trail would be lost amongst the old lava flows, making the ice caves the perfect hideout. [7]


     There also exists a legend about the Shoshone Indian Ice Caves. It is believed that a Shoshone Indian princess named Edahow was buried in the ice of the caves. Should that ice ever melt, she would rise up again and wander the caves for the rest of eternity. As stated previously, the ice did melt in the 1940s and was restored in the 1962. Since the ice did melt, there have been stories of people seeing a young Indian princess wandering about in the caves. [2][9]


     For those interested in visiting the Shoshone Indian Ice Caves, they should come prepared with a good pair of shoes they won't slip in and a jacket, no matter how hot it may be outside.