Landforms of British Columbia 1976 - Department of Geography

the strait. It is suggested that the boundary between the two areas is also the boundary
between two structural regions. Further studies of this sort will contribute
greatly to the physiographic knowledge of the submarine topography on the continental
shelf.
Glaciation within the Georgia Depression was intense. Ice pouring westward
from the Coast Mountains and eastward from the Vancouver Island Ranges
coalesced in the strait to form a glacier which flowed southeastward and southward,
and escaped to sea westward through Juan de Fuca Strait. The depression in part
is of structural origin, but in part was over-deepened by ice erosion. Low-lying
rock surfaces were stripped of weathered material and were shaped, while elsewhere
glacial materials were deposited as ground moraines or as outwash plains, of which
Hernando, Savary, and Harwood Islands are remnants.
[Reference: Bancroft, J. A., “ Geology of the Coast and Islands between the
Strait of Georgia and Queen Charlotte Sound,” GeoZ. SU~V., Cunu&, Mem. 23,
1913.1
[Photograph: B.C. 673 : 42.1
Georgia Lowland
The Georgia Lowland south of Sayward includes parts of numerous islands
as far south as the Malaspina Peninsula north of Powell River. From there south-
eastward a narrow strip on the mainland 2 to 10 miles wide, together with the few
offshore islands, constitutes the lowland. High areas between Sayward and Menzies
Bay, on Quadra Island, and on Texada Island lie within the Georgia Depression,
rising as monadnocks above the prevailing lowland surface.
The Strait of Georgia and Johnstone Strait essentially follow the contact
between the granitic rocks of the Coast Intrusions of Jurassic age and older rocks
of the Vancouver Group and others which lie to the west, The Georgia Lowland
is underlain by granitic rocks as well as by inliers of older formations.
As in the Hecate Lowland to the north, accordant summits represent remnants
of a dissected late Tertiary erosion surface, which is warped and rises gradually
eastward from Georgia Strait until it is sufficiently high in the Coast Mountains to
be completely dissected and destroyed. In an intermediate zone between elevations
of 2,000 and about 4,000 feet, some small remnants of the Tertiary erosion surface
may still be seen (see N.T.S. Sheets 92 G/l2 and G/13), but it is below 2,000
feet elevation within the Georgia Lowland that remnants are more extensive and
are to be seen as gently sloping upland surfaces (see N.T.S. Sheet 92 K/6).
The Fraser Lowlund (see Plate VIB) is a part of the Georgia Lowland, from
which it differs in being a low-lying area of depositional rather than erosional origin.
Its triangular shape includes the delta of the Fraser River, extending eastward from
Point Grey for 70 miles to Laidlaw, thence southwestward to the coast at Belling-
ham. The area is bounded on the north by the Pacific Ranges of the Coast
Mountains and on the southeast by the Skagit Range of the Cascade Mountains, all
of which rise abruptly from the plain.
The Fraser Lowland in the New Westminster area is described by Armstrong
in Geological Survey of Canada Paper 57-5. It “ consists of extensive low hills
(in this report called uplands) ranging in elevation from 50 to 1,000 feet separated
by wide, flat-bottomed valleys. The uplands are of four main types: (1) a core
of unconsolidated deposits with rolling, hummocky surfaces of glacial till and
glacio-marine deposits; (2) a core of unconsolidated deposits with commonly flat,
terraced surfaces of glacial outwash; (3) a core of bedrock overlain by a thin
mantle of glacial and glacio-marine deposits; and (4) raised marine deltas with a
possible core of bedrock . . . .
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