The urban hoodoo formation in Whitemud Ravine is a unique geological feature that showcases the interplay of sedimentary deposits and erosional processes within an urban environment. While not true hoodoos in the traditional sense, these formations mimic the appearance of hoodoos with their pillar-like structures protruding from the walls of the ravine.
Historic Formation of Whitemud Creek
Prior to its current form as Whitemud Creek, the area surrounding Whitemud Ravine was once part of a much larger system that included a substantial lake. During the retreat of the glaciers at the end of the last Ice Age, meltwater accumulated in depressions left behind by the glacial activity. One such depression in the Edmonton region eventually formed a vast lake, known as Glacial Lake Edmonton.
Glacial Lake Edmonton was a proglacial lake, meaning it formed in front of the retreating glacier. It was one of several large lakes that formed across North America during the Pleistocene Epoch. The lake existed approximately 11,000 to 13,000 years ago and covered much of what is now the Edmonton region, including the area surrounding Whitemud Ravine. As Glacial Lake Edmonton fluctuated in size and depth, its shorelines shifted, leaving behind distinctive sedimentary deposits. The lake would have been fed by meltwater from the retreating glacier, as well as by rivers and streams draining the surrounding landscape. This influx of sediment contributed to the formation of fertile soils and deposited layers of sediment that would later become part of the landscape features seen in Whitemud Ravine.
Over time, as the climate warmed and the glaciers continued to retreat, Glacial Lake Edmonton drained away. With the retreat of the glaciers, the landscape began to undergo extensive erosion. Rivers and streams carved out valleys and ravines, while wind and weathering further sculpted the terrain. The remaining water formed smaller bodies of water, including rivers and creeks, such as Whitemud Creek. The creek carved its way through the landscape, following the path of least resistance, and played a significant role in shaping the ravines and valleys in the area. The softer sedimentary layers in the Whitemud Ravine area were particularly susceptible to erosion, leading to the formation of the distinctive landscape features we see today.
Whitemud Ravine's “Urban Hoodoos”
Nestled within this trail lies a striking exposure of grey-white dirt, bearing resemblance to the iconic badlands of southern Alberta. Small urban hoodoos grace the side of this exposed embankment, partially carved into the terrain. These hoodoos form through a fascinating process: a hard sandstone layer overlaying soft clay. As wind and rain gradually erode the bank, the softer clay layers succumb more readily than the resilient sandstone, resulting in the formation of a sandstone cap atop columns of clay. The clay present here is known as bentonite clay. When moist, it transforms into a slippery and adhesive mud; upon drying, it develops a surface texture akin to popcorn, marked by intricate cracks.
Whitemud Ravine and its features, including the “urban hoodoos”, were primarily shaped by erosional processes over millions of years. While the walls in Whitemud Ravine share a similar geological material appearance to natural hoodoos found in other regions, there are some key differences. Natural hoodoos typically form in arid and semi-arid environments where the underlying rock layers consist of alternating hard and soft materials, such as sandstone capped by a layer of harder rock like limestone. In contrast, the ”urban hoodoos” in Whitemud Ravine are formed from sedimentary deposits of clay or soil, rather than rock, and are sculpted by erosional processes over time. Natural hoodoos often exhibit more intricate shapes and formations due to the unique geological conditions of their respective environments. Unlike freestanding natural hoodoos, the “urban hoodoos” in Whitemud Ravine are integrated into the walls of the ravine, composed of sedimentary deposits such as clay, silt, sand, and gravel. While both types of formations result from differential erosion, these urban hoodoos are part of the overall stratigraphy of the ravine walls rather than standalone pillars. The sedimentary layers are eroded at different rates, creating hoodoo-like structures that protrude from the ravine walls. Despite these differences, both natural hoodoos and urban hoodoos result from similar principles of erosion and differential weathering.
Natural Hoodoos
Natural hoodoos are geological formations characterized by tall, thin spires of rock that protrude from the surrounding landscape. These formations typically consist of a resilient capstone perched atop a narrower pedestal, creating the iconic hoodoo shape. Hoodoos form through a process known as differential erosion, which occurs when layers of rock erode at different rates due to variations in their hardness, composition, and resistance to weathering. In regions with arid or semi-arid climates, such as the southwestern United States and parts of Alberta, Canada, hoodoos often develop from sedimentary rock formations composed of alternating layers of hard and soft materials. Over time, the softer layers erode more quickly, undercutting the harder layers above and creating the distinctive hoodoo structures. Factors such as wind, water, frost action, and chemical weathering contribute to the erosion process, sculpting the hoodoos into a variety of shapes and sizes. Natural hoodoos are renowned for their striking appearance and are often found in scenic landscapes, attracting visitors from around the world to marvel at their beauty and geological significance.
Famous Alberta Hoodoos
Alberta is home to several notable hoodoo formations, each with its own unique characteristics and appeal. Some of the most famous hoodoos in Alberta include:
- Drumheller Hoodoos: Located in the Badlands near the town of Drumheller, these hoodoos are perhaps the most iconic and widely recognized in Alberta. Composed of sedimentary rock formations capped with harder rocks, the Drumheller Hoodoos have been sculpted by erosion over millions of years. They are easily accessible via hiking trails and offer stunning views of the surrounding Badlands landscape.
- Writing-on-Stone Hoodoos: Situated within Writing-on-Stone Provincial Park in southern Alberta, these hoodoos are renowned for their cultural and natural significance. The area is home to ancient Indigenous rock art, as well as unique geological formations including hoodoos formed from sandstone and mudstone. Visitors can explore the park's hiking trails and interpretive programs to learn about its rich history and geology.
- Hoodoos Trail in Banff National Park: While not as prominent as the hoodoos in Drumheller or Writing-on-Stone, the Hoodoos Trail in Banff National Park offers a picturesque viewpoint of hoodoo formations overlooking the Bow River Valley. These hoodoos are composed of sedimentary rocks eroded by wind and water over time. The trail provides a relatively easy hike with stunning panoramic vistas of the Canadian Rockies.
- Horse Thief Canyon Hoodoos: Located near the town of Drumheller, Horse Thief Canyon is home to a series of hoodoos similar to those found in the main Drumheller Hoodoos area. The canyon offers hiking trails and scenic viewpoints overlooking the Red Deer River Valley, providing opportunities for exploration and photography amidst the unique geological formations.
- Castle Provincial Park Hoodoos: In southern Alberta, Castle Provincial Park features hoodoos formed from sandstone and shale layers. These hoodoos are part of the expansive Castle Wilderness Area and offer a remote and rugged landscape for outdoor enthusiasts to explore. The park's trails provide access to the hoodoo formations as well as stunning mountain scenery.
Summary
One of the distinguishing features of the urban hoodoos in Whitemud Ravine is their location within an urban environment. Situated within the city of Edmonton, these formations offer residents and visitors a glimpse into the natural history and geological processes that have shaped the local landscape over time. They serve as a reminder of the dynamic relationship between urban development and the natural environment. Overall, the urban hoodoo formation in Whitemud Ravine is a remarkable example of geological diversity within an urban setting. While not as well-known as some of Alberta's more famous hoodoo formations, it offers valuable insights into the geological processes that have shaped the region and provides a connection to the natural world within the cityscape.
Logging Requirements
To log this EarthCache, visitors are required to answer a series of questions about the geological features they observe, rather than signing a physical logbook. To complete your found log for this EarthCache, please provide answers to the following questions prior to logging your find. Do not include your answers in your public log post; please send them to me in a private message. If full logging requirements are not met, your log may be removed without notice.
- What geological processes contributed to the formation of these urban hoodoos in Whitemud Ravine?
- How does the formation of the urban hoodoos in Whitemud Ravine differ from that of natural hoodoos found in other regions?
- What is the primary geological composition of these urban hoodoos?
- What do you estimate the height and width of this section of urban hoodoos to be?
- Noting that bentonite clay has the ability to hold a significant amount of moisture, consider how the texture may vary depending on moisture levels. Please describe the texture of the clay during your visit, providing details about the observed texture variations.
- Please describe the stark contrast between the hoodoo section and the walls just beyond it in this section of Whitemud Ravine. Why do you think this landscape changes so quickly?
- Please share a photo of your visit to these urban hoodoos along with your Found log. If you prefer not to be in the picture, kindly include a personal item to indicate your presence at the site.
From geocaching.com: An EarthCache teaches an earth science lesson. The cache page must include logging tasks that help teach the same lesson. Geocachers must complete the tasks before they log the EarthCache as found.