Landforms of British Columbia 1976 - Department of Geography

along most shorelines is so resistant that little erosion has taken place in the short
time since the Pleistocene (see Plate VIA). The only extensive beaches are on the
west coast of Vancouver IsIand between Ucluelet and Tofino, aIong the north and
east coasts of Graham Island, and along the east coast of Vancouver Island. They
have developed along stretches of shallow depth where unconsolidated glacial
materials and easily eroded Tertiary rocks have provided an abundant supply of
sand to them. Elsewhere, steeply plunging submarine slopes have not allowed
beaches to be retained.
On the west coast of Vancouver Island, beaches are invariably associated with
areas of Tertiary sediments or with occurrences of unconsolidated glacial materials.
At Florencia Bay and Wickaninnish Bay wide sandy beaches have resulted
from wave attack on Pleistocene till and outwash sands and gravels extensively
exposed along the shoreline. Both beaches are exposed to the open ocean and to
violent wave attack, which constantly cuts into the sea cliffs of unconsolidated
material to provide sand and coarse materials which accumulate on the beaches.
At Long Beach strong southwesterly winds have blown sand eastward to form
an area of dunes several hundred feet wide and several miles long.
Extensive post-Pleistocene beaches have been developed along the north and
east coasts of the northeastern part of Graham Island. The beaches are at the
present sea-level and in some instances may be as much as 30 feet above it. Except
for the bedrock at Skonun Point, Yakan Point, and Tow Hill, the entire distance
between Entry Point and Rose Spit, a distance of 26 miles, is continuous wide
sandy beach (see Plate XLVB). The foreshore is broad, 500 feet or more, because
of the combination of gentle slope and wide tidal range. The backshore area, which
may be several hundred feet or more in width, abuts a succession of beach ridges,
elongated parallel to the shoreline, that represent post-Pleistocene sea-level stands
that are higher than the present.
The beaches extend down the east coast of Graham Island from Rose Spit to
Tlell, a distance of 43 miles. To the mouth of Oeanda River, 16 miles south of
Rose Spit, the foreshore area is steeper and narrower than on the north coast and
the material is more gravelly. Northwesterly trending sand dunes extend for
several hundred feet back from the backshore. No bedrock is exposed between
Oeanda River and Rose Spit. Low cliffs (cutbanks) of unconsolidated Pleistocene
material extend southward from Fife Point. The beaches of the east coast are
being formed from the erosion of unconsolidated glacial outwash materials along
the shore. Sand derived in this manner is transported northward along the coast
by longshore drift to extend Rose Spit northward into Dixon Entrance. The spit
appears to have started at the base of Argonaut Hill and to have grown northward
for 12 miles to its present position, possibly in more than one stage.
“Wave and current action on the east coast is transporting material northward
to Rose Spit, thence westward along the north coast toward Mass.9 Inlet.
“The sand of the north and east coast beaches clearly is derived from Pleistocene
deposits which have been eroded by wave action along the east coast south of
Argonaut Hill. In places, pebbles on the north coast beaches are derived by
erosion from outcroppings of Tertiary formations at Skonun Point, Yakan Point,
and Tow Hill. The Pieistocene deposits were probably derived in part from Tertiary
sediments and volcanics of Graham Island, but part of the material no doubt
comes from more distant sources.“*
Sea cliffs for the most part are developed along sections of coastline where
there are occurrences of readily eroded rocks such as the softer Cretaceous and
Tertiary shales and shaly sandstones, or extensive accumulations of till and glacial
* Holland, Stuart s.. am! i%%rnilh, H. w., “ InYePtigation Of Beach Sands,” B.C. Depl. Of MBes. 19%.
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