GrainsWest Fall 2018

Fall 2018 Grains West 24 BY TODD KRISTENSEN How geology and geography shaped Alberta agriculture THE SOILS AROUND US are not the soils that our grandfathers broke,” explained Darwin Anderson, a retired professor from the University of Saskatchewan who spent his career studying Prairie dirt in Western Canada. Anderson explained that soils are constantly changing. To understand how they took shape in Alberta requires a look back, not just at a century of family farming that altered soil productivity, but at millions of years of strange and powerful events. Modern farming in Alberta is based on a thin sliver of soil with a thick history. The story of every field in Alberta begins over 180 million years ago when the province sat, smooth and flat, inside a geological plate that began slowly crashing into islands and belts of land to its west. The collision, which ended about 50 million years ago, lifted the mountains of B.C. and Alberta and tilted this province down to the east. Since then, sand, silt and gravel poured down the slopes and laid the bedrock basement beneath our rubber boots. All was peaceful until two million years ago when ice sheets over one kilometre thick carved a new landscape. Nigel Atkinson of the Alberta Geological Survey likens these glacial forces to bulldozers that moved loads of rock across the province, cut out swaths, and smoothed the Prairies. Atkinson explained that most fields in Alberta owe their current shape to the legacy of ice or its meltwater. Importantly for modern agriculture, ice wiped away existing dirt and reset the soil formation clock to zero. FEATURE Unlike other regions of the globe, where soils that have been leached for millions of years, Alberta’s ground is a youthful 10,000 years old. The ice age produced fertile soils—growing glaciers were like a blender that chopped the compact bedrock of acidic shale and sandstone in with basic limestone to make a porous smoothie of sediment with a healthy pH. Ancient ice that covered Alberta melted to the west and east to create a hallway or ice-free corridor. For thousands of years, meltwater from the west delivered sediment to glacial lakes in this corridor that were dammed by ice to the east. Picture water flowing down a ditch to a blocked culvert. Large parts of the province were covered in a trapped water body larger than the Great Lakes where fine materials, such as clays and Terra Firma Photo:ProvincialArchivesofAlberta