Spelunking Tour of Lick Creek Cave
October 22 and 23, 2005
Cave Geology -- Lick Creek Cave is a solution cavity in Madison Limestone. Madison Limestone is composed of the calcite shells of animals that lived in a shallow saltwater sea about 330 million years ago. Most of the limestone is made of shells of tiny animals which floated near the surface of the sea, but whose shells sank to the bottom when they died. However, there are some layers with abundant larger fossils. The Madison Limestone is about 1700 feet thick. About 300 million years this area was uplifted so that the limestone was above sea level. As groundwater percolated through the cracks in the limestone, the fresh water dissolved a cave system. When the area subsided and the Madison Limestone was buried under a thick overburden, the caves collapsed. A second period of prolonged uplift allowed another cave system to form and subsidence eventually resulted in the collapse of that cave system. The current cave, Lick Creek Cave, is part of the third cycle of cave development. One can see the angular blocks of cave collapse breccia from a former cave system in the wall and ceiling of the Dome Room. The cave system was dissolved out of solid rock when the limestone was above sea level, but below the water table (also known as the phraetic phase of cave development). Uplift and erosion of the overburden continued. (Montana has been undergoing slow continuous uplift for the last 50 million years.) When water no longer filled the cave, that is it was above the water table, but plenty of groundwater percolated through the cave, most of the cave decorations or speleothems formed. These include stalagmites, stalagtites, columns, "soda straws", "popcorn", ribbon stone, and flow stone. The white flowstone in the photo on the left is wet. Layer after layer of calcite is being deposited and the flowstone is still growing.
The limestone beds in which the cave is located are tilted at approximately 30° from the horizontal due to an igneous intrusion--the Tiger Butte Laccolith--that forcefully intruded between a couple of sedimentary layers and folded the overlying rocks. The igneous rock can be seen in outcrops along the road on both sides of Tiger Butte. There are some outcrops of white marble along the road where the heat of the intrusion was sufficient to metamorphose the Madison Limestone.
Cave Conservation -- Lick Creek Cave is heavily visited and heavily vandalized. There are graffiti on the walls. Most of the stalagtites that are easily reached have been broken off and taken. People have brought string, beer bottles, pop cans, and a lot of other trash into the cave and even built camp fires inside the cave. Such actions are vandalism and are punishible by law. In spite of the misuse there is plenty of space, plenty of passages, and plenty of things to see to make the spelunking tour a rewarding experience. Please take nothing but pictures and leave nothing but footprints!
Cave Safety -- Lick Creek Cave is a "wild cave." It is uncommercialized. No paved walkways. No lights. No snack bar. No souvenir shop. No bumper stickers. Cave safety is stressed on the spelunking tour. All participants shall wear a hard hat equipped with a lamp bracket and chin strap. Carbide lamps fit on the helmet so that both hands can be used. A 9 mm nylon safety rope is used to demonstrate proper belaying techniques. Please bring an extra change of clothes so that you do not "muddy up" the car you ride in on the way back to Great Falls.
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