Lewis & Clark Caverns EarthCache

Lewis and Clark Caverns

This is a seasonal earthcache as the caverns are only open from the beginning of May to the end of September. The caverns are only accessed by guided tour and there is a small entrance fee, which is well worth it when you tour the caverns. See the related website for hours of operation and cost. To log this cache you will need to answer the following questions, which can be found on the interpretive signs along the self-guided trail leading up to the caverns’ entrance, and by using your observation skills inside the caverns.

The Lewis and Clark Caverns are what's known as a 'maze cave' to scientists. This means that the many individual rooms in the cave form a network, much like that of a sponge. The largest known limestone caverns in the northwest, these remarkable caverns were actually never seen by the famous American explorers Lewis and Clark, but instead, were discovered by two local ranchers in 1892. The caverns do overlook the trail that Lewis and Clark took along the Jefferson River.

The limestone at these caverns is a sedimentary rock composed mostly of ancient skeletal, and calcium rich, remains of marine organisms.  Over time the remains of these organisms become layers on the sea bed where time and pressure petrify them to become the carbonate mineral known as ‘calcite’. As well, the limestone may contain other grains such as silica, clay, silt and sand.  Limestone is easily eroded by water, and these caverns were thought to have been created during the ice age by slightly acidic waters from what is now known as the Jefferson River.

The amazing features found in these caverns include stalactites, stalagmites, columns and helictites and many more calcite formations. All these formations fall under 5 catergories; Dripstones, Flowstones, Seepstones/Erractics, Pool Formations, and Dry Formations/Evaporatives.

See the attached link ‘Lewis & Clark Caverns State Park Cave Formation List’ to see a comprehensive list of all the formations you’ll see in the caverns, including:

Dripstones are the best known formations. When people think of caves, dripstone formations are what leap to mind. There are three basic types. In Lewis & Clark Caverns all the dripstones are made of a crystalline form of Calcium Carbonate known as Calcite. Of these formations you find stalactites, stalagmites and columns in the caverns.

Flowstones are not as well-known as dripstones but are the most widespread cave formation type, almost all caves with formation growth have some form of flowstone. Most are rather bland, but a few such as waterfalls and ribbons are very ornate. You’ll find waterfalls and ribbons here.

Unlike dripstones and flowstones, seepstones do not follow the vertical path of gravity; rather they grow in many different directions which gives them the “Erratic” name. Some of the erratics here are popcorn, helictites and fracture shields.

There are other pool formations that form in and around pools of water. Many of these are perfectly level as they form along the water’s surface tension at the edge of the pool. Here you’ll find shelfstone and rimstone.

Dry formations come in a few different sorts. Some do require water to work, but are deposited as the water dries away. Other formations are also known as evaporatives which were formed under water, but since forming the water has dried up. These unique features include; cave coral, dogtooth spar, boxwork and chert nodules.