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Lava River Cave is a natural attraction just 14 miles northwest of Flagstaff. The natural cave was formed by lava around 700,000 years ago. A 1 mile hike into the cave provides visitors with a geologic and scenic treat.
Around 700,000 years ago, the San Francisco Volcanic field nearby was very active. This set of lava tubes formed within a couple hours of a volcanic eruption. Geologists think this eruption occurred at a volcanic vent in Hart Prairie, not far to the east. A vent is not like a traditional cinder cone or stratovolcano where lava shoots vertical, but quite literally a “vent” where built up lava was able to flow out horizontally. As lava spewed out onto Hart Prairie, the top and sides of the flow began to harden, while the bottom remained very warm. Liquid magma sits comfortably at around 2,000 degrees Fahrenheit. As the bottom remained liquid, it continued to flow. Eventually the lava tubes emptied and cooled off to a point where a large, cylindrical void was left.
Evidence of the lava flow is visible at numerous points in the cave. Most notably is the ripple marks along the floor of the cave. Much like a flowing river, the flowing magma had currents and channels of magma. As the magma hardened, these ripples marks were preserved in stone on the cave floor. Another neat feature are spots known as “splashdowns”. This occurred when rocks from the ceiling fell down into the flowing liquid magma. These are harder to spot but can be found where a large rock seems to be ‘stuck’ in the cave floor with ripple marks going around it. Finally, there are numerous cooling cracks of all sizes found throughout the cave. These occurred as the magma cooled and the rocks solidified.
The lava caves remain fairly cool year round because of the nature of volcanic rocks, and the nature of caves in general. The temperature inside the cave floats between 35 and 45 degrees year round. It is not uncommon to see ice in the entrance to the cave (the coldest part). The entrance itself was discovered in about 1915 by lumbermen working with the Saginaw and Manestee Lumber Company. They stumbled upon the cave entrance when logging nearby. They were probably surprised to find such an extensive cave network accessed only by a single, small hole in the middle of the forest. Nearby homesteaders took advantage of the cool year round temperatures and would frequently take large chunks of ice from near the entrance to the cave back home to keep food and drinks cold. The warmest point in the cave is at the end of the tube.
Hiking the Lava River Caves is a fun experience but often underestimated. While it isn’t a difficult hike, it also isn’t a paved stroll in the park. The entrance to the cave requires navigating over several large boulders (which can be icy in the winter). The inside of the cave varies widely. At certain points, the cave is 30 feet high and very wide. At others, it is less than 5 feet high and requires crouching if you’re a taller person. Be sure to wear hiking shoes, carry water, and at least 2 sources of light (in case you drop/lose one). The cave is very dark and you lose all traces of sunlight very quickly.
Access to the cave is via forest roads. Travel north on Highway 180 for 9 miles. Turn left onto Forest Road 245 and follow it west for 3 miles. Continue left onto Forest Road 171 south for 1 mile until F.R. 171B. Turn left and end at a large parking area. The entrance is a few hundred feet east of the parking area. This is a side trip on one of our trails (F.R. 245/171) in the Flagstaff area, check that page out for more information on getting to I-40 from the cave or exploring the area after you are done with the hike. Some of the roads are closed in the winter time despite the cave being open 365 days a year.
"Lava River Cave: A Natural Museum." Coconino National Forest -. United States Department of Agriculture: Forest Service, n.d. Web. 13 Jan. 2016. <http://www.fs.usda.gov/detailfull/coconino/learning/nature-science/?cid=stelprdb5275785&width=full>.
"Lava River Cave." Coconino National Forest Recreation. United States Department of Agriculture: Forest Service, n.d. Web. 13 Jan. 2016. <http://www.fs.usda.gov/wps/portal/fsinternet/!ut/p/c5/04_SB8K8xLLM9MSSzPy8xBz9CP0os3gDfxMDT8MwRydLA1cj72BTn0AjAwgAykeaxcN4jhYG_h4eYX5hPgYwefy6w0H24dcPNgEHcDTQ9_PIz03VL8iNMMgycVQEADoWIdk!/dl3/d3/L2dJQSEvUUt3QS9ZQnZ3LzZfME80MEkxVkFCOTBFMktTNUJIMjAwMDAwMDA!/?ss=110304&navid=110000000000000&pnavid=null&cid=FSE_003741&recid=55122&ttype=recarea&navtype=BROWSEBYSUBJECT&pname=Coconino%2BNational%2BForest%2BRecreation%2B-%2BLava%2BRiver%2BCave>.
Photo copyright of Kubby Photography. Used with permission.