Landforms of British Columbia 1976 - Department of Geography
Landforms of British Columbia 1976 - Department of Geography
Landforms of British Columbia 1976 - Department of Geography
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the strait. It is suggested that the boundary between the two areas is also the boundary<br />
between two structural regions. Further studies <strong>of</strong> this sort will contribute<br />
greatly to the physiographic knowledge <strong>of</strong> the submarine topography on the continental<br />
shelf.<br />
Glaciation within the Georgia Depression was intense. Ice pouring westward<br />
from the Coast Mountains and eastward from the Vancouver Island Ranges<br />
coalesced in the strait to form a glacier which flowed southeastward and southward,<br />
and escaped to sea westward through Juan de Fuca Strait. The depression in part<br />
is <strong>of</strong> structural origin, but in part was over-deepened by ice erosion. Low-lying<br />
rock surfaces were stripped <strong>of</strong> weathered material and were shaped, while elsewhere<br />
glacial materials were deposited as ground moraines or as outwash plains, <strong>of</strong> which<br />
Hernando, Savary, and Harwood Islands are remnants.<br />
[Reference: Bancr<strong>of</strong>t, J. A., “ Geology <strong>of</strong> the Coast and Islands between the<br />
Strait <strong>of</strong> Georgia and Queen Charlotte Sound,” GeoZ. SU~V., Cunu&, Mem. 23,<br />
1913.1<br />
[Photograph: B.C. 673 : 42.1<br />
Georgia Lowland<br />
The Georgia Lowland south <strong>of</strong> Sayward includes parts <strong>of</strong> numerous islands<br />
as far south as the Malaspina Peninsula north <strong>of</strong> Powell River. From there south-<br />
eastward a narrow strip on the mainland 2 to 10 miles wide, together with the few<br />
<strong>of</strong>fshore islands, constitutes the lowland. High areas between Sayward and Menzies<br />
Bay, on Quadra Island, and on Texada Island lie within the Georgia Depression,<br />
rising as monadnocks above the prevailing lowland surface.<br />
The Strait <strong>of</strong> Georgia and Johnstone Strait essentially follow the contact<br />
between the granitic rocks <strong>of</strong> the Coast Intrusions <strong>of</strong> Jurassic age and older rocks<br />
<strong>of</strong> the Vancouver Group and others which lie to the west, The Georgia Lowland<br />
is underlain by granitic rocks as well as by inliers <strong>of</strong> older formations.<br />
As in the Hecate Lowland to the north, accordant summits represent remnants<br />
<strong>of</strong> a dissected late Tertiary erosion surface, which is warped and rises gradually<br />
eastward from Georgia Strait until it is sufficiently high in the Coast Mountains to<br />
be completely dissected and destroyed. In an intermediate zone between elevations<br />
<strong>of</strong> 2,000 and about 4,000 feet, some small remnants <strong>of</strong> the Tertiary erosion surface<br />
may still be seen (see N.T.S. Sheets 92 G/l2 and G/13), but it is below 2,000<br />
feet elevation within the Georgia Lowland that remnants are more extensive and<br />
are to be seen as gently sloping upland surfaces (see N.T.S. Sheet 92 K/6).<br />
The Fraser Lowlund (see Plate VIB) is a part <strong>of</strong> the Georgia Lowland, from<br />
which it differs in being a low-lying area <strong>of</strong> depositional rather than erosional origin.<br />
Its triangular shape includes the delta <strong>of</strong> the Fraser River, extending eastward from<br />
Point Grey for 70 miles to Laidlaw, thence southwestward to the coast at Belling-<br />
ham. The area is bounded on the north by the Pacific Ranges <strong>of</strong> the Coast<br />
Mountains and on the southeast by the Skagit Range <strong>of</strong> the Cascade Mountains, all<br />
<strong>of</strong> which rise abruptly from the plain.<br />
The Fraser Lowland in the New Westminster area is described by Armstrong<br />
in Geological Survey <strong>of</strong> Canada Paper 57-5. It “ consists <strong>of</strong> extensive low hills<br />
(in this report called uplands) ranging in elevation from 50 to 1,000 feet separated<br />
by wide, flat-bottomed valleys. The uplands are <strong>of</strong> four main types: (1) a core<br />
<strong>of</strong> unconsolidated deposits with rolling, hummocky surfaces <strong>of</strong> glacial till and<br />
glacio-marine deposits; (2) a core <strong>of</strong> unconsolidated deposits with commonly flat,<br />
terraced surfaces <strong>of</strong> glacial outwash; (3) a core <strong>of</strong> bedrock overlain by a thin<br />
mantle <strong>of</strong> glacial and glacio-marine deposits; and (4) raised marine deltas with a<br />
possible core <strong>of</strong> bedrock . . . .<br />
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