Three billion years ago, wow is that a long time ago, the Precambrian shield was in its formative stages. The prominent escarpment is to the north of where you stand with the river rapids being the southern edge. This once large behemoth of a geological shield began to be worn away through erosion, becoming much smaller and rounded hills. The following formative years in the area will be explored in requirements one and two.
A rapid is a section of a river when the river's bed has steep gradient causing an increase in water velocity and turbulence. A rapid is a river feature between a run (a smoothly flowing part of a stream)
and a cascade or waterfall.
- Niagra Falls
In river rapids, the river is shallower and rocks are exposed above the flowing water. As the flow of water crashes against and around and over the rocks, air bubbles become mixed in with it and portions of the surface become white, hence the term "whitewater." Rapids occur where the bed material is highly resistant to the erosive power of the stream in comparison with the bed downstream of the rapids.
The Saint Mary's Rapids are caused by event occuring long ago in the past during and after the last Ice Age. When the glacier's retreated, rocks that the ice had picked up as it traveled south were left in this area of the river as the ice melted. The melting ice also caused the formation of the two Great Lakes this river traverses.
The water cuts through a hill of Jacobsville sandstone, giving the steeper gradient necessary for rapids to form. Most of the 1,850 cubic m/s flow is now captured and diverted to three power plants. The rapids once thought to be a travel hiderence, quickly became a means to power an up and coming metropolis.
Your mission is to find the sign along the boardwalk entitled Geology of Sault Ste. Marie.
REQUIREMENTS:
1. What happened to the Lake Superior basin 1 billion years ago? What changed 600 million years ago?
2. Why did what occurred in #1 ultimately lead to the formation of the northern most Great Lake once the glaciers came and retreated?
3. The water falls through the rapids about 6.4 meters from Great Lake _____ to Great Lake _____.
4. Even this river valley was once a large glacial lake until water levels further subsided. What was exposed as the valley took shape with falling water levels which led to the formation of the rapids you are visiting?
Not completing any one of the requirements within 3 days of a found log will lead to log deletion.
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