The common landslide types (circular-arc failure and
noncircular-arc or translational failure) can be analysed and
the risk of failure calculated. The major causes of slope
failure are the removal of material at or near the base of a
slope by natural EROSION or human excavation; additional weight
placed on the upper part of a slope by natural or human
agencies; an increase of water pressure within the slope by
rainfall or snowmelt, local irrigation or leaking sewer or water
mains. Land-use studies in the design stages of a project can
avoid or minimize subsequent landslide activity. The 1929 Grand
Banks EARTHQUAKE triggered submarine landsliding of about 100
km3 of sediment, the largest historic event in Canada. The
resulting tsunami caused loss of life along the south coast of
Newfoundland. Submarine transatlantic cables were ruptured by
the sediment flow. Clayey soils were deposited in the CHAMPLAIN
SEA, which invaded the St Lawrence and Ottawa River lowlands
between some 10 000 and 12 000 years ago. These