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In Post 271: A Rivulet of Water I came across a small stream of running water in an otherwise frozen landscape. As odd as this phenomenon was I did not have a good explanation for what caused it, but I theorized: “Is it discharge from a human-made source higher up in the forest? Is it a warm spring? Unlikely, but possible.“. As it turns out I was on to something. As I was doing the research on the geology of the River Valley and the Whitemud Creek for the January 1 post I came across information indicating that there are indeed springs in the Whitmud Ravine. I put the two things together and realized that the rivulet of water in the middle of winter could be coming from a ground water spring higher up in the ravine. This just had to be investigated. Said and done, yesterday returned to the location of the tiny creek. It had snowed during the night and the trail was in pristine untouched condition.
As I made my way up the trail the rivulet was still there, its blackness in stark contrast to the fresh white snow.
I started following the creek upstream. Occasionally it disappeared under the snow and I had to either make an educated guess based on the slope of the terrain from which direction it might be coming from or, if I stayed completely still, I could hear the trickle of water leading me upstream to where it made appeared again. Progressively the rivulet became wider, at times reaching a meter across.
I had been following the rivulet for quite some distance into the forest and up the slope of the ravine when, all of a sudden, it changed color. Quite abruptly it went from black to rusty brown color.
As I continued making my way through the understory along the steep slope the color became more intense rust colored.
I could not resist digging up some of the sediment with my fingers. The substrate was creamy and slippery with the color staining my fingers.
Finally I seemed to have reached the source of the river. I was high up in the ravine now and there were numerous pools of water with thick rusty colored sediment covering the bottoms. The water was no longer flowing and was completely still.
It turns out that this is indeed a spring and the rust colored sediment is tufa, a type of limestone. The tufa forms here because of groundwater springs emerge bringing warm groundwater bubbles up, loses carbon dioxide and goes through numerous other chemical reactions. Calcium carbonate comes out of the water to form stone. Tufa is typically fragile and crumble with your fingers and is often full of trapped moss, sticks and other vegetation. The rusty colored slime is created by bacteria breaking down iron oxide for energy.
May the curiosity be with you. This is from “The Birds are Calling” blog (www.thebirdsarecalling.com). Copyright Mario Pineda.