Logging Requirements:
WARNING: the trail down to the stream is challenging and technical. There is a "rope" to assist the descent. Descent is NOT part of the earthcache, but is an extra bonus!
1. From the trail, identify at least ONE Concoidal fracture in the strata. Estimate the SIZE of the fracture and the COORDINATES of the fracture you find. 2. From the trail, look for the line between the dolostone and shale. You will be able to see this line as the color changes from a very fine grained brownish gray dolostone (on top) to a darker courser (porous) shale. Estimate/Measure width of Dolostone at that location. 3. Since the shale is a cave-bearing formation, is there a cave developing behind the falls? If so, why geologically? If not, why not geologically? 4. (optional) Take a picture of yourself with the falls or the Dolostone strata behind you.
The hike:
You will start at Morningstar Mill. From there you will hike down the ONLY significant trail in the park (westward). You trail is a gradual descent through the Niagara Escarpment in Short Hills Provincial Park.
About Decew Falls:
Decew Falls cascades 22 metres (72 feet) into a bowl-shaped amphitheatre just behind the mill. The Decew Formation is a fine grained brown-grey dolostone of the silurian age. The rock here can be found in a thickness of up to 12 feet. The strata is underlain by the rochester shale, making it a cave bearing formation. The shale is somewhat impervious to water, so the water within the rock pools above the shale. The waters constant movement erodes and dissolves tunnels below. The DeCew Formation can be seen as far west as Hamilton, the obvious conchoidal fracturing being a feature that immediatly identifys the strata.
In order to complete this eartcache, you DO NOT need to go "down the rope" to the streambed, though that is an adventure worth doing! All logging requirements can be done for the "easy" overlook portion of the trail.
Conchoidal Fracture: This type of fracture is a bit unusual in geology, since it is only possible when there is no natural plane or separation in the rock. A conchoidal fracture looks a lot like a "conch" shell, since it usually breaks in a "rippling curve" that looks similar to a shell. Obsidian, flint, and other types of rocks that break in this way were used by native Americans throughout history to create sharp instruments such as arrowheads, spears, and other tools.
Congrads to Kreamer&BearsKrew for FTF (First to Finish logging requirements) on 9/20/2011.
Reference:
Geology of Decew Falls Blog http://www.niagaragreenbelt.com/listings/73-natural-habitats-a-features/629-decew-falls-geology.html
Conchoidal Fracture (Wikipedia) http://en.wikipedia.org/wiki/Conchoidal_fracture