Contents

Petrified Garden

Map of the Cave Showing the Location of the Petrified Garden (Source: Oregon Caves Image Library)

The Petrified Garden is the first room in the cave featuring classic cave formations. Depositional cave formations are collectively known as speleothems. They were able to establish here because there is enough disFlowstone crowds the trail through Petrified Gardens (Source: Oregon Caves Image Library)tance between this room and the entrance.

Being further from the entrance allows for more stable air temperatures, which prevents acid dew and ice wedging from destroying the speleothems faster than they can form. However, due to the airflow change created by the construction of the nearby Connecting Tunnel in 1937, ice wedging occurred in the Petrified Garden before the mid 1990s. This caused some of the formations to break or crack. However, many formations still remain including soda straws, stalactites, flowstone and draperies.

 

Geology

Cave Formations

Speleothems, or cave formations, are considered secondary deposits because they form after there is an established passage and entrance. This is because formations need open space and air to establish (Bates and Jackson 632). Speleothems are created by watCave formations accumulate calcite drop by drop; this drop is about the size of a pinky nail (Source: Oregon Caves Image Library)er entering a cave passage, which allows the carbon dioxide held in water to escape to the air. With the loss of carbon dioxide, water can also no longer hold onto calcite. Therefore it is forced to deposit it, which allows for the establishment of the cave formations (James 183; Dreybrodt 543-548). There are various types of cave formations. Most are made out of calcite, but they can look very different from one another. This is caused by water coming into the cave at various rates and in different directions (Dreybrodt 543-548; Hill and Forti 691-692).

 

In the Petrified Garden, there are a variety of speleothems. Soda straws are small, tubular formations hanging on the ceiling (Bates and Jackson 740). Stalactites are often larger and more conical but are also attached to the ceiling (Bates and Jackson 640). Draperies are linear formations that look like curtains (Bates and Jackson 197). Flowstone can also be seen covering the sides of the room and is formed when water travels in sheets (Roth 230).

Airflow

In the late 1980s, people noticed that certain formations in the Petrified Garden were cracking and some were falling off. This is the result of the Connecting Tunnel diverting freezing air through the Petrified Garden, which triggered ice wedging. The problem was resolved by installing airlock doors in 1993 at the head of the Connecting Tunnel and Exit Tunnel (Roth 9).

Some of the Straws in Petrified Garden Were Broken by Ice Wedging (Source: Heather Neis)

 

References

Bates, Robert and Julia Jackson, ed. Glossary of Geology. Alexandria: American Geological Institute, 1987. 

Dreybrodt, Wolfgang. “Speleothem Deposition.” Encyclopedia of Caves. David Culver and William White, ed. Burlington: Elsevier Academic Press, 2005. 543-548.

Hill, Carol and Paolo Forti. “Speleothems: Carbonate.” Encyclopedia of Caves and Karst Science. John Gunn, ed. New York: Fitzroy Dearborn, 2004. 690-692.

James, Julia. “Carbon Dioxide-Enriched Air.”. Encyclopedia of Caves and Karst Science. John Gunn, ed New York: Fitzroy Dearborn, 2004. 183-184.

Roth, John. “Interpretive Manual for the Monument’s Showcave”. Cave Junction: Oregon Caves National Monument, 2011. 9.