Landforms of British Columbia 1976 - Department of Geography

ase of the Sumas till in the Fraser River delta was found to be 11,300 +300
years old. This, in effect, is the date of the last Pleistocene ice advance there.
The geological time interval immediately following the Pleistocene is called the
Recent. It began about 10,000 years ago with a warm dry period, the “ climatic
optimum,” which in turn was followed by a cool moist period that resulted in the
“ little ice age.” In British Columbia the climax of the “ little ice age ” was
about 450 years ago,* at that time mountain glaciers advanced to their maximum
extent since the Pleistocene. The recession of glaciers from the limits reached dur-
ing the “ little ice age ” has varied from place to place, but in general it began within
the last 200 years. The climate of British Columbia is becoming progressively
warmer, and the present recession of glaciers, which has been at an accelerated rate
since 1920, is merely the latest episode in this “ little ice age.” It may mark the end,
or it may not. The uncertainty is not resolved by recent studies of temperature
records, which indicate that the rising curve of average annual temperatures reached
a peak in 1940 and since then has fallen.?
[References: Nasmith, H., “ Late Glacial History and Surficial Deposits of
the Okanagan Valley,” B.C. Dept. of $kes, Bull. No. 46, 1962; Flint, R. F.,
“ Glacial Geology and the Pleistocene Epoch,” John Wiley & Co., New York;
Kerr, F. A., “ Quaternary Glaciation in the Coast Range,” Jour. Geol., Vol. 44,
1936, pp. 681-700; Davis, N. F. G., and Mathews, W. H., “Four Phases of
Glaciation from Southern British Columbia,” Jour. Geol., Vol. 52, 1944, pp.
403-413; Armstrong, J. E., and Tipper, H. W., “Glaciation in North Central
British Columbia,” Am. Jour. Sci., Vol. 246, 1948, pp. 283-310; Armstrong, J. E.,
“ Surficial Geology of New Westminster Map-area,” Geol. Surv., Canada, Paper
57-S; Atlas of British Columbia, B.C. Natural Resources Conference, 1956, Map
No. 4, “ Glacial Geology;” Glacial Map of Canada, Geological Association of
Canada, 1958; Mathews, W. H., “ Glacial Lakes and Ice Retreat in South Central
British Columbia,” Trans., Roy. Sot., Cunad$, Vol. 38, Sec. IV, 1944, pp. 39-57;
Mathews, W. H., “ Fluctuations of Alpine Glaciers in Southwestern British
Columbia,” Jour. Geol., Vol. 59, No. 4, 1951, pp. 357-380; Hansen, H. P., “ Post
Glaoial Forests in South Central and Central British Columbia,” Am. Jour. Sci.,
Vol. 253, 1955, pp. 640-658; Heusser, C. J., “ Late Pleistocene Environments of
North Pacific North America,” Am. Geogr. Sot., Spec. Publ. No. 35, 1960;
Matthes, F. E., “ Glaciers ” in Hydrology, edited by 0. E. Meinzer, Dover
Publications, 1942.1
[Photographs: B.C. 360:49; B.C. 501:94; B.C. 893:19; B.C. 983:53;
B.C. 1406:ll; B.C. 2005:30; B.C. 2007:3; B.C. 2214:46, 68, 88.1
RIVERS OF BRITISH COLUMBIA
Rivers are most important in British Columbia, a land that is largely
mountainous and where more than 75 per cent of the surface lies above 3,000
feet elevation. They permit the crossing of mountain ranges on water gradients
in major valleys, and thus provide easy access to all parts of the country. Further-
more, they provide migration routes for spawning salmon, opportunities for the
development of hydro-electric energy, water for agricultural and domestic use, and
in other ways contribute to the economy. However, it is the role of rivers as
agents of erosion and transportation in the development of the landforms of
British Columbia that justifies specific descriptions of the river systems in this
section.
* Mathews, W. H., Jour. Gtd., Vol. 59, No. 4, 1951, p. 378.
t Simons, W. D., U.S.G.S., Prof. Paper 424% 1961, p. B 17.
105