Geology Chronicles

Montana | davidmrule

The Most Photographed Stone East of the Mississippi

Argentina is okay

A very happy Valentine's day to all my rock lovers. Platonic or not.

The American Niagara Falls without water (New York, 1969).

The American Falls is the second of three waterfalls that make up the Niagara Falls.  It has a massive talus (rock pile) at its base as a result of a series of natural rockslides in 1931 and 1954.  In the late 1960s, however, there were concerns that further rockslides could erode the falls entirely.  A joint American-Canadian commission decided to “dewater” the falls for five months, so that a geological survey of the rock face could be carried out.

So in June 1969, over 1,200 trucks dumped nearly 28,000 tons of rocky fill into a dam upstream of the falls [1 top right & 2], diverting the flow of the Niagara River away from the American Falls and towards the much larger Horseshoe Falls.  This process took three days.  The US Army Corps of Engineers could then begin their investigation.

The riverbed was criss-crossed with a series of cracks [4] that were examined for possible links to rockslides, and the engineers mechanically bolted and strengthened any faults that they found [7]. They drilled test-cores to check for instabilities, planted instruments to monitor rock movements in several locations, installed steel bolts and cables to stabilize the rocks around Luna Island and Bridal Veil Falls, and drilled drainage holes to relieve hydrostatic pressure at several points.

A temporary walkway was installed 6 metres from the edge of the dry falls, allowing tourists to explore the landscape.  Only two corpses were found during these five months, which was surprising given the falls’ history of accidents and suicides.

There was a plan to remove the huge mound of talus [9], but it was abandoned because of the high cost for what would be basically aesthetic reasons.