If you have been following my blog, then you’ll know that this week I have been discussing peculiar geological features from around the world. The example that I’ll be using in todays post will be my final excursion here on Earth and then it’s off to the cosmos! Through my research to identify “oddball geological features,” one thing has become abundantly clear– we know very little about our planet and solar system. That’s not to discredit the hard work and observations scientists have made for the better part of 2000 years. I’m simply conveying that in the grand scheme of things, we have much more to learn. It is my hope, that through my writing I will be able to inspire some of you to consider carrying out the human inhibition and to a certain extent, tradition, to simply ask question, “why?” With that being said, today we’ll be discussing the Zhangye Danxia Landform in the Gansu Province of China– more commonly called the Rainbow Mountains by westerners.
Admittedly, these rainbow technicolor mountains– that appear to be from a trippy Simpson’s episode– were fairly difficult to research. This is largely due to the lack of scholarly articles on the feature itself. I suppose from a geological point of view the formation of the Zhangye Danxia Landform is somewhat of a banal subject, which I will explain in a bit. However, I still find it strange that something so beautiful wouldn’t be considered a great entry point and example to inspire the next potential geologist in the world. They are truly something to be in awe over.
When first looking at the images of the Rainbow Mountains, I assumed the colors must have been saturated by means of Photoshop. In some instances this was true, but upon further investigation, it would seem most of the photos are unedited. If you’ve read the description below the photos I have shared above, you’ll see that it's rain that actually draws out the vivid contrast of colors. In Fig. 1, this is what the mountains look like after being saturated by rain. In Fig. 2, they are still impressive, but visually are bit more lackluster in comparison.
So how did they form? Though the information at hand was limited, knowledge that I have retained through my studies and the articles that I have procured, I was able to come to a conclusion. The topography of the Rainbow Mountains are the product of the deposition of sediments (sedimentation) that occurred over eons and plate tectonics.
Given the location of the Danxia formations, it is clear the tectonic plate stresses that created the Himalayan Mountains (i.e. convergent plate boundary), caused the once horizontal sedimentary layers to be folded and thrusted over time. This can be identified by the anticline and syncline of the technicolor layers. The graph above should help give you a better understanding of how to identify the anticline and syncline of a rock face. After being distorted from plate tectonics, weathering (e.g. wind, rain) slowly carved out the valleys, crevasses and cliffs in the region, exposing the layers of rock. It should be noted, that similar examples of this type of geological feature can be seen in Peru and British Columbia, Canada. However, it would appear the colors in those examples aren't nearly as vivid.
As for the color of the layers themselves, this can be explained through paleoclimatology. At the time of deposition of the sediments, it is clear that the climates in which they were created, changed drastically over a very long period of time (millions of years). The biggest tell that this is the case, are the bluish-greenish-gray layers. This typically indicates that there was some sort of organic plant matter at the time of deposition or it contains a mineral called glauconite, which is found in marine environments. As for the red and and yellow colored layers, the red indicates the presence of the iron-rich mineral hematite, which oxidizes (i.e. rusts). This could have occurred at the time of the rock formation or when the layers were exposed to the atmosphere. The yellow indicates the presence of sand and clay, leading me to believe it was an arid climate at the time of deposition.
All science-y stuff set aside, I think it goes without saying that the Rainbow Mountains of China fall under the classification of “oddball geological features.” The more of these examples I curate, the more I come down with the travel bug. Maybe after I’m finished with school, my blog will help fund that adventure. If you missed the previous two posts in this series and enjoyed this article, please check them out. They discuss the Sailing Stones of the Playa and the Chocolate Hills of Bohol. If you contribute to the subjects dealing with earth sciences here on Steemit, be sure to check out Geopolis and join the Discord channel!
Bibliography:
https://en.wikipedia.org/wiki/Zhangye_National_Geopark
http://www.educationworld.com/a_lesson/lesson-plan-booster/china-zhangye-danxia-geology.shtml
https://www.geologyin.com/2015/09/rainbow-mountains-in-chinas-danxia.html
https://en.wikipedia.org/wiki/Sedimentary_rock
https://en.wikipedia.org/wiki/Hematite
https://en.wikipedia.org/wiki/Glauconite
https://en.wikipedia.org/wiki/Paleoclimatology
https://en.wikipedia.org/wiki/Syncline
Classroom studies and casual reading.