During the last (Wisconsin) ice age, the region of the vicinity of Niagara Falls was covered by the Labradoran ice sheet, only the most recent in a sequence of the advance and retreat of such continental glaciers throughout the Pleistocene. The last glacier, like the previous ones, mechanically removed all soil, and hence all vegetation on the areas over which it passed. The present flora, then, totally derives from vegetated areas south and west of the ice front. The Niagara region was essentially free of glacial cover around 12,300 years ago, with the establishment of Lakes Erie and Ontario
The surface of the rock, on which the deposit forming Goat Island is made, is smoothed and scratched, as are the surrounding surfaces, both in the rapids and on either bank of the river" (Hall, 1843), testifying to the passage of the continental ice mass over the area. Porter (16 Ann Rep Comm, 1900) also reported glacial markings on the exposed bedrock of Goat Island. In a popular account of the geology of the area, Tiplin (1988) indicated that at the east end of Goat Island and the Three Sister Islands, the visible ridges are "roches moutonnees": eroded pre- or inter-glacial ridges formed first by river-erosion and subsequently modified, "polished," by the glacial ice-mass.
Much of the aspect of the bedrock on Goat Island, once exposed in the southeastern portion of that island, is hidden beneath the topsoil deposited there in 1911.
So what are roches mountonnees?
Roche moutonnée, (French: “fleecy rock”) English sheepback, or sheep rock, glaciated bedrock surface, usually in the form of rounded knobs. The upstream side of a roche moutonnée has been subjected to glacial scouring that has produced a gentle, polished, and striated slope; the downstream side has been subjected to glacial plucking that has resulted in a steep, irregular, and jagged slope. The ridges dividing the upstream and downstream slopes are therefore perpendicular to the general flow direction of the former ice mass.
Glacier movement can create these asymmetrical rock formations and hills. The glacier wears down the rocks gradually, forming one smooth, sloped side, but pulls rocks away from the other side as it passes over, forming a sharper, more-jagged slope. These formations can be used to determine the direction of glacier movement.
If you visit during the time of high water diversion for power generation, or even during a strong westerly wind, much more of the rock is exposed and you can clearly see the glacial erosion features. As you look east from the posted coordinates, you will see a green wall of water about eight feet high that seems to be flooding down.
To get credit for this earthcache, please send answers to me for the following questions:
- Estimate the height of the cascade you see.
- Are any of the roche moutonnee visible during your visit?
- Explain in your own words how the roche mountonnee formed.
- Post a picture of yourself (face not required) or a personal item at the posted coordinates.
sources: wikipedia and britannica