Welcome to Xiaoliuqiu — An Island of Geological Wonder! (TUFA + TRAVERTINE)
In this Earth Cache, you will learn about a special by-product of limestone — known as tufa and travertine with a brief overview of coastal erosion (chemical solution), and how these — the byproduct of limestone and the forces of coastal erosion — helped "maintain", and at the same time, "reshape", a one-of-a-kind rock formation right here on the coast of Xiaoliuqiu known as Rat Rock since the rock resembles a rat sitting down looking out into the sea. So, upon learning all there is to know about tufa, travertine, and coastal erosion, and the circumstances that brought about this "permanent" rock formation, you will be ready to put on your Earth Science Caps and get geological on location here at Xiaoliuqiu Island. And after you answer the task questions and complete all your Limestone/ Erosion Studies and Observations (which can all be found at the bottom of this page), you can log a “Found It!” for this Earth Cache. I hope you enjoy! Are you ready? Let's begin . . .
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How is it Possible that Rat Rock can be so different from its "Cousin" (Guanyin Rock — GC9K8MG) 100 Meters Away?
As you can tell from the Geocaching Map, there is another rock formation about 100 meters away (GC9K8MG) from Rat Rock! And a quick stroll on over to that location you will notice that even though these two rock formations are just a hop, skip, and a jump away from each other, you will quickly notice that Guanyin Rock is full of holes everywhere whereas Rat Rock appears to be unscathed by such "destruction". Why is this? Well, as you observe this area, you will notice virtually everywhere you look there is limestone — a special kind of rock that can be either biologically formed or chemically formed. Biologically formed limestone comes from the coral that once lived in the ocean here. And when that coral died, their skeleton remains lithified or transformed into what we know as limestone. Now when it comes to chemical limestone, basically the calcium carbonate — the "magic ingredient" that shell-building organisms use when making their shells — is not in those animals but actually in rainwater! Yep, that same chemical can be evaporated and then later precipitated upon rocks, thus forming chemical limestone. Now, the "regular" or rather biological limestone will contain elements of chemical limestone, thus a lot of the time being referred to as biochemical limestone, which can arguable be the "stronger" kind of limestone as it contains both "strong" parts from biological means and chemical means. So how does all this information translate into what the Rat Rock is all about compared to its "cousin" — Guanyin Rock and why does Rat Rock look more "well-built" and more "intact"? Well, it just so happens that at this particular location just a hundred meters away from Guanyin Rock, the limestone here that makes up Rat Rock is "magically" a byproduct of limestone known as tufa or travertine. Basically, tufa and travertine, in theory, are the same kind of rock — they are both a kind of limestone that forms in the same way as regular limestone but tufa forms in water with cooler temperatures whereas travertine forms in water with much warmer to hotter temperatures. Tufa and travertine can arguably be considered or categorized as the "tougher" kinds of limestone as they are less porous, meaning they are less susceptible to organisms "drilling" holes in it or from weathering mechanisms causing too much destruction, relatively speaking of course. So, through the power of diagenesis or the hardening of the sediments into "tougher" limestone, tufa and travertine are born here at Rat Rock and is the reason behind its unique "completeness".
So we see that Rat Rock is virtually void of those borings or holes you can so easily see 100 meters away at Guanyin Rock (GC9K8MG). But Rat Rock still takes on a unique shape — a rat that is sitting and looking out into the ocean. So obviously this rat didn't just magically appear so what caused it to look the way it is? Your answer is coastal erosion — more specific solution erosion. But wait — didn't I say before that tufa and travertine are less porous, and therefore tougher at resisting erosion forces? Yes, that is true — tufa and travertine are better at resisting biological erosion or the breaking down and removing of rock by organisms. However, the power of the ocean waves combined with the acidic rain are still going to have an effect on this rock, and cause solution erosion or the dissolving of the rock, but just at a much slower speed than its neighbor, Guanyin Rock.
So there you have it. Rat Rock got "luckier" when it came to the powers of Mother Nature and got the "stronger genes" — a "better" kind of limestone that makes it more resistant to biological erosion but won't be 100% resistant to the powers of the ocean!
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Logging Requirements
Xiaoliuqiu is an island of Geological Wonder with so many unique landforms and hidden geological treasures, with one in particular — Rat Rock — which is a place where both bioerosion and coastal erosion "fight" to keep this rock alive!
In order to log a Found It! for this Earth Cache, please go to the Posted Coordinates to complete the following tasks:
1. First, feel the ocean water and take note of its temperature and time of day, and overall weather conditions. Based on what you learned about tufa and travertine, would you consider Rat Rock to be mostly composed of tufa, travertine, or both?
2. Based on what you have learned about tufa and travertine, and based on your "experiment" in Task 1, do you feel you were right in identifying the "correct" kind of limestone here at Rat Rock? Why or why not? How did you come to your conclusions?
3. Based on what you have learned about tufa and travertine, and based on what you have learned about its "power" to resist both biological and coastal erosion, which section(s) of the rock appear to be the "safest" from such forces? How about the weakest? What do these sections tell you about the overall composition of the rock itself? How did you come to your conclusions?
4. Based on everything you have learned about tufa and travertine, and based on all your on-site observations and tasks, do you feel this rock is in fact composed of that byproduct of limestone? Why or why not? How did you come to your conclusions?
5. Optional — Post a photo of yourself or a "Geocaching" item identifying yourself here at "Rat Rock."
You may log a Found It! on this cache after you have completed the tasks and emailed me the answers. If there are any issues with your answers, I will contact you. And as a friendly reminder, please do not post any of the answers in your logs. Thank you for visiting this Earth Cache. I hope you enjoy your time here at Rat Rock.