Edworthy Park - Bow Valley Overview EarthCache

This location provides a great overview of the geological history of the Bow Valley.

If you look across the valley beyond the new Children’s Hospital, you will see Nose Hill. Nose Hill and Broadcast Hill (behind you), are remnants of the high plains that existed in this area before ancient rivers and glaciers carved the land down to present levels.

In the middle distance, the new Children’s Hospital, the Foothills Hospital and the University of Calgary are at approximately the same elevation as the Edworthy benchland. The Edworthy benchland is a fairly thin layer of glacial till, silt and gravel over the Porcupine Hills Formation tertiary bedrock. However, the north bench has a much different geological profile – the Porcupine Hills Formation mudstone is topped with a thin layer of pre-glacial gravel and then much thicker layers firstly of glacial till, silt and gravel and then most recently post-glacial silt and gravel. Much of the silt was deposited on the bottom of Glacial Lake Calgary.

During the Quaternary Period Ice Age (from about 2 million to 11 thousand years ago), two different glacier flows moved into the Calgary area. The Cordilleran glaciers flowed eastward from the Rocky Mountains and met the Laurentide Ice Sheet flowing into the area from the northeast. As the Cordilleran glaciers melted, the run-off water was blocked by the Laurentide Ice Sheet; Glacial Lake Calgary was formed. Then, as the front edge of the Laurentide Ice Sheet melted back toward the east, Glacial Lake Calgary slowly moved location. At different times, the current Fish Creek, Elbow River and Bow River valleys were filled with arms of the lake. In the western part of Calgary, the Lake bottom became the terrace (or bench) you see today, underlying communities such as Brentwood and Silver Springs as well as the Children’s and Foothills Hospitals and the University of Calgary.

Try to imagine standing here around 15,000 years ago, watching waves on Glacial Lake Calgary lap against the sides of Nose Hill. From this vantage point looking east, you might have seen the Laurentide Ice Sheet that covered the eastern part of the city.

Today, immediately east of the posted coordinates is a small coulee, which is a fairly steep-sided valley with transient water flows. A little further east, you will notice a small bluff. When I was visiting Edworthy park to obtain the coordinates for this earthcache, a long-time resident of Calgary explained to me that this bluff was once used as a Bison jump and how, as a young boy in the 1930s he would pick buffalo bones from the base of the cliff. If you look north and very slight west, down in the river valley and near the base of the Edworthy benchland, you should be able to spot a small pond. The same long-time resident told me the pond is fed by a natural spring. Apparently, it makes for a nice skating pond in the winter. Back in the 1930s, there was a spring-fed horse trough on the Edworthy farm, where the kids would enjoy a cool drink on warm summer days. And, of course, just a short distance away is the current-day Bow River and valley bottom.

SOURCES: Calgary’s Natural Parks – Yours to Explore by Jim Foley published by Calgary Field Naturalists’ Society, 2006; Mr. Trevoy; Geological Survey of Canada.

To log this cache, please complete the following:

1. E-mail the cache owner (do not post) your estimate of the elevation difference from your location to the present-day valley floor.
2. E-mail the cache owner (do not post) your estimate of the distance to the benchland on the far side of the valley. By way of clarification / consistency, what we're really looking for is your estimate of the width of the valley. Use the Alberta Children's Hospital as your reference point on the north side of the valley.
3. E-mail the cache owner (do not post) the names of the individuals remembered on the bench located at the posted coordinates.
4. We enjoy watching the seasons change through your photos, so we invite you to post a photo of yourself and/or your GPSr taken near the posted coordinates. Please be sure your photo doesn't include the details from the park bench needed to answer the previous question.