Geoscape Whitehorse – Geoscience for a Yukon Community This is a colourful, jargon-free, graphics-rich poster which explains earth science issues in the Whitehorse valley. It includes information on human use of the Yukon River, groundwater, earth and glacial history, copper mining and radon: basic geoscience knowledge for adult citizens and as the starting point for science projects from grade 6 upward. Link here directly to the Geoscape Website Or download the following brochures: Yukon River Geo-time Glaciation Volcanic Eruptions Whitehorse Copper Belt Yukon River

Four geological aspects and thee environmental issues are arranged around a winter view of the city (Figure 1 PDF). They are: 1) changing use of the Yukon River with time; 2) de-glaciation of the valley; 3) Neogene volcanism; 4) copper mining; 5) and 6) municipal and rural water supply; and 7) radon gas hazard. The content of each delivers a succinct message. Two of these are described here:

Legacy of Mining: The prosperity of Whitehorse was augmented by mining of nearby copper –rich rocks three times in the last century. At least 18 sites of former mining lie within the city limits; all have been decommissioned and one is used for landfill. The poster shows how the copper minerals formed, and how they were extracted. Current environmental issues are the re-vegetation of a large area of dry tailings, and potential contamination of groundwater in the vicinity. Acidic drainage is not a problem in the abandoned workings or tailings because the rocks hosting the copper contain abundant limestone, and iron sulphide was sparse in the ore, as illustrated in Figure 2.

Care of water supply: By showing citizens where their water comes from and where the sewage goes, the poster encourages wise water use. For example, an oblique aerial photograph and cut-away view shows the path followed by groundwater to reach municipal wells in the Riverdale subdivision. Damming of the Yukon River to form Schwatka Lake caused a rise in the groundwater table, killing trees around nearby pothole lakes. Beneath these lakes (designated a natural recreation area) lies a pre-Ice Age river channel (Chadburn buried valley; Figure 3) along which groundwater moves northward beneath Riverdale subdivision to the city’s water wells. Currently this aquifer is of high purity, with the added benefit of maintaining 4°C (warmer than water drawn from Schwatka Lake) flow many tens of kilometers through city water mains without freezing. The message is that contamination of the source area or beneath the subdivision will affect this useful resource.

The poster, 140 x 90 cm (5’ x 3’), is published by the federal Geological Survey of Canada and printed in English and French. It is available for $15 from the Whitehorse Mining Recorder in the Elijah Smith building, 102-300 Main St., Whitehorse, Yukon Y1A 2B5; (867)667-3266, as well as Geological Survey of Canada (Natural Resources Canada) sales outlets in Vancouver and Ottawa.


Figure 1 (PDF): Geoscape Whitehorse, one of seven colour posters in the Geoscape series (reduced from 140 x 90 cm size). To print out individual parts of the poster, please go to the Geoscape Website

Figure 2: Simplified chemical reactions to show the difference between drainage from acid-generating rock and from tailings of Whitehorse copper mining.

Figure 3: Groundwater flow beneath Riverdale subdivision toward the municipal wellfield. The oblique aerial view is northward toward downtown Whitehorse.