Lemieux's Legendary Leda Landslide
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10,000 years ago much of the Ottawa Valley and Eastern Ontario were covered by the Champlain Sea, formed by glaciers of the most recent ice age. The sea lasted about 3,000 years until a gradual process of isostatic rebound occurred, bringing the area back up above sea level. Glacial sediment, clay and silt, were deposited throughout much of this area, making what is known as Leda Clay. This clay can absorb a large amount of water and can thereby liquefy. If disturbed, and the protective outer layer of soil is removed, the liquefied Leda clay will become unstable and move, causing a chain reaction that results in landslides.
About the town of Lemieux: Being situated right on the banks of the South Nation River was an excellent location for an Eastern-Ontario mill town: Lemieux. It was established in 1850 and grew into a farming community with the prevalence of dairy and crop farming in the area. In 1971 a small landslide occurred along the South Nation River just upstream from Lemieux. In 1989 the South Nation River Conservation Authority and Ministry of Natural Resources for Ontario purchased all the homes in Lemieux. From 1989 until 1991 all homes and buildings were either moved or demolished. “With the closing of the church, the Parish of Lemieux ceased to exist on August 4, 1991.”
This is very fortuitous because less than two years later, after heavy rains, the saturated Leda clay started a landslide. At 3:30pm on 20 June 1993 the Leda clay under 17 hectares at the former town site washed into the South Nation River. “Debris traveled 1.7 km upstream and 1.6 km downstream, completely blocking the river for several days. The costs related to this event were estimated at $12 500 000.”
To log this earthcache you must go to the posted coordinates. There is a plaque and an information panel at that location, make note of the information about Lemieux’s Legendary Leda Landslide. Look around the field and spot the large white cross nearby.
1. Take a picture of yourself and your GPSr in front of the cross.
2. Send me an e-mail with the following information:
a. The coordinates of the cross.
b. What were the volumetric dimensions of the crater?
c. What was the date and location of Canada’s deadliest Leda clay landslide?
Please be respectful at the cemetery, no pets allowed.
(No hints available.)
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Coordinates are in the WGS84 datum