On Saturday morning, a hydrologist and a meteorologist were planning to go for a hike. One person looked at the weather radar, said something about 2″ of precipitable water in the air mass and strong divergence in the upper atmosphere, and sagely decided to stay inside and dry. The other person muttered something about canopy interception and runoff generation mechanisms and decided to head out on the hike. The only question is: how wet did the hydrologist get?
My destination for the day was Crowders Mountain State Park, about 30 minutes west of Charlotte, North Carolina on the border with South Carolina. The state park protects forest land and two mountains rising 300 m above the mostly flat Piedmont landscape. These are what Americans call monadnocks, Europeans call inselbergs, and South Africans call kopje, all terms to describe isolated mountains that presumably have survived erosion that has worn away the surrounding landscape. Usually monadnocks are made of weathering-resistant rocks like quartzite.
Crowders Mountain and nearby The Pinnacle are made of kyanite-rick quartzite, though the kyanite here is gray rather than its typical blue color. The rocks of the surrounding lowlands are mica-rich schists and much more easily erodible. Strong vertical foliation at Crowders Mountain and the Pinnacle have resulted in greater than 30 m high cliffs, popular with rock climbers.
I am told that the mountains afford a spectacular view of the surrounding area. In good weather, I should even be able to see one of my field areas from the summit, but I was not so lucky on Saturday.
Fortunately, most of the moisture held off until after I was done hiking, and the forest canopy kept me dry enough to hike without raingear, so I didn’t notice any overland flow at all. In harder rains, impermeable clay-rich red soils of this region do generate quite a bit of surface runoff, so the scientist in me was a bit disappointed to miss it, but the hiker in me was glad not to be soaked.
I did manage to find some flowing water in the park though – a headwater stream making big meanders across a alluvial valley bottom, and occasionally splashing over on some exposed bedrock. This stream seemed pretty typical of relatively pristine Piedmont headwater streams, but those undisturbed streams are very hard to find, so I may have to come back to this one for research in the future. In the meantime, the little stream will continue the work it and its predecessors have been doing for ~500 million years – conveying that precipitated water downhill and trying to erode away those hard, hard quartzite mountains.
Categories: by Anne, outcrops, photos
Tags: erosion, geomorphology, hydrology, landscape evolution
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