Mystery Cave 2

Mystery Cave II

Mystery Cave II is connected to Mystery Cave I by underground passages. The cave has a number of different features because it is formed in Stewartville Dolomite instead of the DuBuque Limestone of Mystery Cave I. Dolomite is a harder rock being made of a mixture of calcium and magnesium carbonate (instead of just calcium carbonate of calcite forming limestone) does not dissolve as readily in the weak acid of carbonated water. The cave passages are often narrow or keyhole shaped caverns over fissures. The larger passages are round caverns with sediments concealing the fissures below. The joints in the rock seem to control the solution of the rock with a strong horizontal component. The Stewartville Dolomite is below or underneath the DuBuque Limestone. This indicates that the Stewartville Dolomite is an older formation (the oldest rocks are laid down first and the newer rocks are layered on top of them).

The photo below left shows the entrance to Mystery II. The photo below right shows one of the water eroded passages near the cave entrance.

The two photos above show a rare cave structure called raft cones. These are such a rare formation that these raft cones are the only ones in caves that are visible on a public tour. Only one other known cave in New Mexico has raft cones. This lake (or pool) is about 9 feet deep so the raft cones that are just sticking up over the surface are about 9 feet tall.

Raft Cone Formation: At the surface of the water a skim coating of calcite (called calcite rafts) can form as the water evaporates from the calcite saturated pool. When a drop of calcite saturated water falls from above it breaks the surface tension of the water causing a small pile of calcite to sink to the bottom of the pool. When the drops of water keep coming from the same spot - and landing in the same spot - the calcite at the bottom of the pool starts to form these small tower shapes called raft cones. The name comes from the calcite rafts that first formed at the surface and the cone shape created as they build up over time.

This flowstone has been radiometerically dated (radioactive decay is used to determine the age) to be 450,000 years old. That means that the cave where the flowstone is being formed had to be here before this 450,000 year old stone began forming.

These photos of cave side passages are typical of the many side passages in the cave. Passages are often keyhole shaped like the above right photo. A narrow joint will widen and then constrict again as the water follows the joints in the rock.

In these photos stalactites and stalagmites grow as water saturated with calcite releases the dissolved carbon dioxide which causes the calcite to precipitate.

Stalactites form when the drops of water hang on the end of the original stalactite and the carbon dioxide escapes like the carbon dioxide bubbles in a just opened bottle of pop.

Stalagmites form when water drips at the same place over time, giving the carbon dioxide time to escape before it runs down the side of the stalagmite.

The photos below show a limestone formed on top of original sediment. When flood waters came in again later the sediment was washed out and the shelf structure was formed. At the top (bottom left photo) there is the beginning of a couple of stalagmites, underneath them are the "roots" of the stalagmite. These look like stalactites but were formed as the stalagmite bottoms grew into the sediment and then the sediment was washed away. When water drips from above it erodes sediment and deposits calcite in the the hole. Eventually the hole get filled and the stalagmite starts to grow above it.