Welcome back to my blog!
Today I will be discussing the Waitomo Caves in New Zealand again in a more in-depth explanation of their formation as it relates to my new understanding of Karst Landscapes.
So, you may be asking "What is Karst?"
Karst is a term that derives from the Jugoslav "kars" which means stone. This term Karst refers to the solution features of a certain type of stone called limestone which occurs on a plateau. Limestone is classified as any rock that has 50 percent or more calcium carbonate contained inside. In fact, the surface of the Earth has 10 to 20 percent limestone.
 |
| Source: Groundwater Systems This picture is a zoomed-in map showing major karst regions in purple. The land masses circled in red are the North and South islands of New Zealand. The karst region shown on the North island is the area of Waitomo. |
Caves as Part of Karst Landscapes
The idea here is that limestone and dolomite are both susceptible to karst development. This can lead to the formation of valleys, sinkholes (dolines), and caves. These formations can occur because of a weathering process called dissolution, where material erodes.
So how did the Waitomo caves form anyway?
Well, there is a debate over how caves form! The two methods suggested are a Deep Phreatic reaction and a Shallow Phreatic reaction. Let me explain below and then I will tell you which I think made the Waitomo Caves.
Deep Phreatic Reaction
In a Deep Phreatic Reaction, the formation occurs below the water table. A blind river goes into the soluble limestone underneath and fills or carves in empty spaces via dissolution. The water source then gets closed off and the caverns are left, along with whatever water has pooled in them.
 |
| Source: Under Florida This image is a visual diagram of the Deep Phreatic Reaction methof of cave formation. The blind river flows into a fissure in the limestone creating a cave and leaving water to pool. |
Shallow Phreatic Reaction
In a Shallow Phreatic Reaction, cave formation happens while the limestone is absorbing water and becoming saturated and weak. This area is exposed when the water table drops. The new cave is made at the water table's former level. This activity of the water table dropping exposes the cave to a zone of aeration, while the water carries away the eroded limestone.
 |
| Source: Geschichteinchronologie This image shows the Shallow Phreatic Reaction formation method. The water table was once at the former level and is now at the current water table level. When the level was high, the vulnerable limestone in the area became saturated and weak. Then, when the level dropped to its current state, the saturated stone eroded and was carried with the water table, leaving a cave in its place. |
My Hypothesis
Based on what I learned, my hypothesis is that the Waitomo caves were formed because of a Deep Phreatic Reaction because the entrance to the cave is an opening in the top of the cave which can allow a flow of water to form the cave. There is also a large amount of water pooling at the bottom.
 |
| Source: Stay Base This picture shows the pooling of water in the bottom of the cave and a group of people attached to a tether that helped them descend into the cave's entrance. |
That's it for now! Tune in next time!
-----------------------------------------------------------------------------------------------------------------------
Resources:
Image Resources
After, M. (1997). Cave Forming By Groundwater [Digital image]. Retrieved April 2, 2017, from http://www.geschichteinchronologie.com/welt/wasser-u-grundwasser01-d/021-cave-forming-by-groundwater-ENGL.png
Groundwater Systems [Digital image]. (n.d.). Retrieved April 2, 2017, from http://images.slideplayer.com/39/10887337/slides/slide_27.jpg
North, L. (2016, October 19). Karst Diagram [Digital image]. Retrieved April 2, 2017, from http://underflorida.com/images/karstdiagram.png
Waitomo Tubing Cave [Digital image]. (n.d.). Retrieved April 4, 2017, from http://cdn.stayatbase.com/image/resize.php?url=images/blog/new-zealand/waitomo_tubing_cave.jpg&width=1600
Article Resources
New Zealand Ministry for Culture and Heritage Te Manatu Taonga. (2015, October 19). Limestone country – Te Ara Encyclopedia of New Zealand. Retrieved April 03, 2017, from http://www.teara.govt.nz/en/limestone-country
Under Bowling Green. (2016, October 19). Retrieved April 03, 2017, from http://underflorida.com/learn.html
No comments:
Post a Comment