Welcome to the Devil's Oven Earthcache. Please read logging requirements as set out below in order to log a find. Please send me an email with the required information, and do not post any answers in your log. Pictures are always encouraged, however, be sure that they do not give away any of the answers!
What is a Pothole?
A pothole is a smooth, bowl-shaped or cylindrical hollow, generally deeper than wide, found carved into the rocky bed of a watercourse. Other names used for riverine potholes are pot, (stream) kettle, giant's kettle, evorsion, hollow, rock mill, churn hole, eddy mill, and kolk.
How are potholes created?
The list of ingredients is pretty short. Bedrock, turbulent water and sediment. Without bedrock, potholes won't form because anything less rock-solid will simply be washed away. Potholes are carved from rock, and moving water provides the energy. This leaves only the suspended sediment. It provides the cutting tools for the job. Three ingredients: rock, water, sediment. In essence, nature is acting as a sculptor.
History Of The Niagara River
The following is from the Niagara Falls Tourism website:
The Niagara River and the entire Great Lakes Basin of which it is a part, is a legacy of the last Ice Age. Close to 18,000 years ago, southern Ontario was covered by ice sheets 2-3 kilometers thick. As the ice sheets advanced southward they gouged out the basins of the Great Lakes. Then as they melted northward for the last time they released vast quantities of meltwater into these basins. Our water is “fossil water”; less than one percent of it is renewable on an annual basis, the rest leftover from the ice sheets.
The Niagara Peninsula became free of the ice about 12,500 years ago. As the ice retreated northward, its meltwaters began to flow down through what became Lake Erie, the Niagara River and Lake Ontario, down to the St. Lawrence River and on to the Atlantic Ocean. There were originally 5 spillways from Lake Erie to Lake Ontario. Eventually these were reduced to one, the original Niagara Falls, at the escarpment at Queenston-Lewiston. From here the Falls began its steady erosion through the bedrock.
However, about 10,500 years ago, through an interplay of geological effects including alternating retreats and re-advances of the ice, and rebounding of the land when released from the intense pressure of the ice (isostatic rebound), this process was interrupted. The glacial meltwaters were rerouted through northern Ontario, bypassing the southern route. For the next 5,000 years Lake Erie remained only half the size of today, the Niagara River was reduced to about 10% of its current flow, and a much-reduced Falls stalled in the area of the Niagara Glen.
About 5,500 years ago the meltwaters were once again routed through southern Ontario, restoring the river and Falls to their full power. Then the Falls reached the Whirlpool.
It was a brief and violent encounter, a geological moment lasting only weeks, maybe even only days. In this moment the Falls of the youthful Niagara River intersected an old riverbed, one that had been buried and sealed during the last Ice Age. The Falls turned into this buried gorge, tore out the glacial debris that filled it, and scoured the old river bottom clean. It was probably not a falls at all now but a huge, churning rapids. When it was all over it left behind a 90-degree turn in the river we know today as the Whirlpool, and North America’s largest series of standing waves we know today as the Whirlpool Rapids.
The Falls then re-established at about the area of the Whirlpool Rapids Bridge and resumed carving its way through solid rock to its present location.
Cavitation is a special type of erosion that happens at waterfalls because only at the base of waterfalls is there enough speed to produce enough bubbles close enough to rock to affect it. This is the fastest type of erosion. As the water goes over the falls, it speeds up, loses internal pressure, air escapes as bubbles or cavities. These cavities collapse when the water comes to rest, sending out shock waves to the surrounding rock, disintegrating it.
In order to log this earthcache, please visit BOTH waypoints and email me the answers to the following questions:
1. What three ingredient are required to make a pothole?
2. In your own words, describe how potholes are created?
The Devil's Oven Pothole (posted coordinates)
3. The large pothole seen here is called the Devil's Oven. Describe this pothole, and estimate it's height, and width.
4. How many other potholes do you see in this boulder, and why do you think they vary in size? (hint: all of the potholes are on one side of this boulder).
5. Take an elevation reading.
The Devil's Arch (waypoint 2 reference point)
6. How does the pothole found here compare (height, width, shape) with the Devil's Oven pothole found at the posted coordinates? (Hint: the shape may look the same, but this one is different)
7. Why do you think this pothole is different than the one found at the posted coordinates?
8. Take an elevation reading.
MANDATORY
9. You are required to take TWO pictures in order to log this earthcache. Take one photo from the posted coordinates showing you or a personal item with the Devil's Oven pothole, and take one photo from the second waypoint showing you or a personal item with the Devil's Arch pothole in the background. I have included sample pictures in the image gallery.
Congratulations to Tim Bits on the FTF!