Grand Column
The domepit at the Spiral Stairs opens up into the low-ceilinged room that houses the Grand Column. The Grand Column is one of the largest and oldest formations in the entire cave.
Geology
Room Development
The Grand Column’s room formed below the water table where groundwater slowly dissolved the surrounding marble in all directions. This creates rooms that tend to be rounder and some are wider than they are tall, which explains the low ceilings. However, this room was close to the water table and so water level fluctuations caused it to drain periodically (Palmer 142, Roth 27). Compare this passageway to the ones in between Watson’s Grotto and the Petrified Garden.
Cave Formations
The Grand Column is one of the best examples of a column. A column is simply defined as the joining of a stalactite and a stalagmite (Bates and Jackson 133).
The stalactite was deposited on the ceiling and grew downward, while the stalagmite was deposited on the floor and grew upward. Both form from drops of water, but the stalagmite is dependent upon the drip of water coming from the tip of the stalactite in order to form (Hill and Forti 691).
Once connected, calcite precipitated on the outside of the column, making the formation grow wider.
Bates, Robert and Julia Jackson, ed. Glossary of Geology. Alexandria: American Geological Institute, 1987. 133.
Hill, Carol and Paolo Forti. “Speleothems: Carbonate.” Encyclopedia of Caves and Karst Science. John Gunn, ed. New York: Fitzroy Dearborn, 2004. 691-692.
Palmer, Arthur N. “Passage Types”. Cave Geology. Dayton, OH: Cave, 2007. 139-144.
Roth, John. “Interpretive Manual for the Monument’s Showcave”. Cave Junction: Oregon Caves National Monument, 2011. 27.