What Makes a Cave
NPS Photo by Dan Austin
Materials: A web connection to the following web pages:
· http://www.nps.gov/wica/naturescience/cave-formations-speleothems.htm pictures and discussion about the formations of Wind Cave National Park.
· View the park's video about the cave's unique formation - boxwork
· http://www.cavebiota.com/ is an excellent website on life in a cave. The Levels of Cave Adaption by Jean Krejca Ph.D. explains troglophiles, trogloxenes, and troglobites. Hazel Barton Ph.D's Cave Microorganisms provides an excellent explanation of microbes found in caves. For more information about bats, visit:http://batslive.pwnet.org/resource/index.php
Wind cave is quite different from other caves. Instead of stalactites and stalagmites, the cave is decorated with boxwork. Boxwork is a crystalline formation that probably predates the cave. It was formed when calcite filled tiny cracks within the limestone. Later, when the cave formed, water dissolved the limestone and revealed the delicate crystal fins that had filled the cracks. Wind cave is known for its length and the maze-like configuration of its passageways. Almost all of the known cave passageways lie beneath a land area of about one mile square making this the most complex maze cave in the world. Few caves are longer than Wind Cave, but none as complex.
Cave Formations or Speleothems:
· Trogloxenes - are casual visitors. They will visit a cave for a short period of time but they have to leave the cave to complete their life cycle. Bats are the creatures most people associate with caves. Wind Cave National Park hosts eight species of bats, six of which are cave-dwelling however they are not commonly seen in Wind Cave. Bats are troglexenes because they must leave the cave to feed.
· Troglobites can spend their whole life in a cave, but they don't need to. Wind Cave has a few salamanders that spend their life in the cave.
· Troglobite are fully adapted to live in a cave. They spend their whole life cycle in a cave. Many do not have eyes or pigment in their skin. In Wind Cave these are the springtails and mites that are found in the far reaches of the cave.
While Wind Cave is one of the longest caves in the world other caves equally as amazing can be very small. Caves can take tens of thousands, or even millions, of years to form, which means we have to work hard to protect them.
1. Before showing the videos, ask the students what they think makes a cave; what they would find in a cave; and what might live in a cave.
2. The short Discovery video discusses the origin of caves and explains how water combines with carbon dioxide to form carbonic acid, which dissolves limestone caves. It quickly discusses the origin of less common caves such as lava tubes, sandstone caves, sea caves, and ice caves. The relationships between groundwater flow and cave formation are discussed along with a discussion of speleothems (formations) and the processes under which they form. The processes are discussed rather quickly, and students may not easily understand them, but the names of the formations are told well. The fragile nature of cave formations is also talked about.
3. After showing the video, compare the opinions of the students with what they learned through the video.
Did You Know?
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