Gorge-us Avakas EarthCache
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A gorge is a steep-sided, narrow valley with a river or stream running along the bottom.
Gorges are formed by the interplay of several geological processes, including erosion, tectonic processes such as vertical uplift and cavern collapse. Erosion by the resident body of water is usually the primary contributor to gorge formation.
A gorge can be formed as a result of a change in rock type at a waterfall. At the base of a waterwall the pressure and hydraulic action of the falling water causes the softer rock which is underneath to erode forming a plunge pool. Over time this continues to erode backwards, undercutting the harder rock which is on the surface. Eventually the over hang is so great that the hard rock can no longer support its own weight and therfore collapses. This process continues and is repeated over hunderds of years causing the waterfall to cut back into the landscape, leaving a steep sided valley known as a gorge.
Gorge formation is accelerated by certain geological processes. Vertical uplift is the rise of tectonic plates creating greater energy potential for a river. This energy is the turned into downward erosion and can cause a gorge to deepen or a new gorge to form.
When the roofs of underground caverns collapse, they can also form or deepen a gorge. Please view the images for a diagram of the formation of a gorge.
Your task at Avakas:
1. At the posted location describe what the flow of water has done to the rock as the gorge has been formed. Is the rock rough or smooth and describe the grain of the rock.
2. look up, what can you see along the gorge?
3. Estimate how deep the gorge has been cut.
4. optional but encouraged, photographs of you in and around the gorge.
Pleaese consider your safety during the winter months when the small river rises and can be dangerous. Think about the last few days rain coming down from the mountains. Dont risk your life, do it another day. There is a risk of rocks falling due to goats on the mountain tops so please take care.
Please log as soon as you like. But if I dont receive your answers within 72 hours of your log it will be deleated.
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