Logging Requirements-please Email me the answers to the following questions. Do not post the answers in your Log!
1) As you descend the stairs into the gorge: you will notice a small cave to your right. What interventions has man made along here? Why do you think he has done this?
2) As you walk towards posted coords, watch for the small caves and caverns in the limestone cliff face to your right. Make sure you look up! Estimate the height of the highest caves that you see. Why do you think a cave formed at this level?
3)At posted coords: Describe what you see here, and give a best guess about how this was formed.
A cave is defined as a hollow or natural passage under or into the earth.
How Limestone caves are formed:
(credit:www.picstopin.com)
Rain water combines with carbon dioxide in the air and dead plant matter on the ground to form a weak version of carbonic acid.
Limestone is a sedimentary rock made up of calcium carbonate. Limestone formed over millions of years, generally from the skeletons of ancient sea creatures, and is a fairly strong rock. But because of the pressure of how it is formed it can have many crevices and fractures. Limestone is a soluble rock and chemically, it is a base.
The rain water, which is now a weak acid, seeps down through the ground and comes into contact with the limestone, a weak base, and seeps into the crevices and fractures. A chemical reaction occurs, and with time (a lot of time) a larger and larger space occurs between the fractures. Eventually after a few hundred thousand years or more, a solutional cave can form.
Sometimes, the water can start to flow along the spaces left by the solution cave process, and as it flows, it erodes the rock. This is what happens with an erosional cave. Other examples of erosional caves are from the actions of wind, sand and waves.
Sinkholes can also occur.
Sinkholes
(credit:http://www.sinkhole.org/facts3.php)
The formation of sinkholes involves most of the same solutional and/or erosional processes that cause limestone caves to be formed. However, sinkholes often form through the additional process of suffosion. Suffosion occurs when unconsolidated, or loosely packed, sediments fill up cavities below them. This causes the area above to 'sink' as the cavities fill. Depending on it's location, a sinkhole can open up to a cave or cavern below.
Enjoy the walk along and the views of Elora Gorge. GPS reception is pretty unreliable here, however the coords should get you close enough so that you can pick out what I wanted you to see. The trail will take you right to it!
Resources:
www.thefreedictionary.com
http://dwb4.unl.edu/Chem/CHEM869A/CHEM869ALinks/rville.k12.mo.us/Cave/caveForm1.html
http://www.icr.org/article/origin-limestone-caves/
www.picstopin.com
https://en.wikipedia.org/wiki/Sinkhole
http://www.sinkhole.org/facts3.php