The Landscape: Geomorphology, Soils, and Climate
The Beaver Hills are distinctly different from the surrounding lands in terms of their soils, terrain and climate. These features have indirectly contributed to another obvious difference: the extent and type of natural vegetation present.
The Beaver Hills/Cooking Lake moraine is a “deadice” or stagnant moraine, formed during the retreat of the glaciers about 9000 years ago (Geowest 1997). Glacial advances ground the underlying bedrock into 'till', coarse to fine debris that was pushed into ridges and mounds as the glacier moved forward. Later, when the glaciers receded, these features remained deposited on the landscape and formed the terrain we see today.
During glacial retreat, the adjacent lands were flooded by glacial Lake Edmonton, but stagnant ice islands remained captured between mounds of till deposits in the Beaver Hills. An equivalent process occurs during spring snowmelt, when deeper pockets and banks of snow caught up in hollows and ditches remain isolated within increasingly snow-free fields.
Eventually, the remnant ice island melted, leaving the complex hummocky (knob and kettle) terrain characteristic of the current landscape. The glacial lakebed of the surrounding lands, in contrast, was left a relatively level plain, with minimal relief. Today, the Beaver Hills form a raised landscape feature (about 750 m above sea level (ASL)), distinctly visible from the surrounding level plains (about 640 m ASL).
Soil development is influenced by underlying parent material (in this case, glacial till), drainage and overlying vegetation. The scattered network of sloughs, bogs and small lakes within the Beaver Hills have moderate drainage through small streams (Geowest 1997). The upland soils resulting from these conditions are predominately the Grey Luvisols commonly found in woodland areas, although Grey Solodized Solonetz soils are also found across the moraine. Black Chernozems, the highly productive soils of agricultural zones, occupy the surrounding plains.
Soils in turn determine agricultural potential, which is much lower in the moraine than that of the adjacent lands. The lack of agricultural suitability is one reason why the Beaver Hills have retained extensive natural woodland habitat, while the adjacent lands have largely been cleared. Climate, too, can affect soil development as well as vegetation. Although only a short distance from Edmonton, weather in the Beaver Hills can be quite different. In fact, the Beaver Hills were originally identified as a disjunct natural subregion based on their similarities in climate and soils with the northern boreal forest (Strong and Leggat 1992).
Although monthly temperatures are typically closer to those of the Central Parkland natural subregion that surround the Beaver Hills, precipitation is about 20% higher than either the Central Parkland or the Dry Mixedwood Boreal subregion to the north. The wetter conditions in the Beaver Hills, in turn, promote plant communities and soils more characteristic of the boreal subregion than the Central Parkland.