Highway 3 crosses the Rocky Mountains from the Rocky Mountain Trench at Elko to the foothills in Alberta. Limestone is abundant here, and mountains of limestone dominate the scenery. This is a good place to stop and take a look at a pullout between Elko and Fernie near the only tunnel on Highway 3.
Tilted layers of limestone rise above Highway 3 just west of the tunnel pullout. The tunnel allows the highway to pass through the lower end of this limestone ridge. The entire length of the eastern Rocky Mountains from Yukon to Montana is limestone country. Limestone is an unusual rock. It is best known because it dissolves slowly in water, and therefore contains caves. Limestone lacks clay minerals necessary for good soil formation and therefore limestone slopes are often bare of vegetation. As a result, limestone mountains have great barren rock peaks. This, along with their distinctive grey colour and prominent layering make the Rockies a striking mountain landscape.
ANCIENT SEAFLOOR MUD
Most limestone was once mud on an ancient tropical seafloor, formed by the accumulation of billions of tiny shells from plankton animals that lived in the overlying warm waters. These tiny animals extracted lime (calcium carbonate) from seawater to form their shells. When the animals died, their shells accumulated as lime mud on the seafloor. Limestone forms from seawater, and so readily dissolves back into water. This is why caves are common in limestone rock. As a result, groundwater within limestone terrain often carries a high load of dissolved lime. In dry limestone country, such as the southern Rockies, you will often find a white coating of lime on the underside of pebbles that lie in soil. This lime is precipitated as lime-rich groundwater seeps to the surface, evaporates, and drops its dissolved load of lime. Where groundwater flows to the surface as springs, mound-like deposits of limestone can form.
COAL COUNTRY!
This is at the boundary between two different geological landscapes. To the south and west are high grey barren ridges and peaks of limestone. To the east, across the Elk River, are lower forested ridges underlain by sandstone and shale. These rocks erode more easily than limestone and form more subdued mountains. Though they form less dramatic landscapes, these sandstone and shale rocks contain vast resources of coal.
Logging Tasks
Please email us the answers don't post them in your log Answer these questions:
1. Why are the limestone formations exposed ?
2. How is limestone formed ?
3. How tall is the limestone cliff across the highway from GZ ?