Nahanni National Park Reserve - Geography

Geography

There are several different landforms in the park that have taken millions of years to form, and give it a diversity not seen in any other national park in Canada. Sediment left by an ancient inland sea 500-200 million years ago had since become pressed into layers of rock. These layers were stacked about 6 km deep and are peppered with fossils, remnants of these ancient sea beds. As the continents shifted, the North American and Pacific plates collided, the force of which pushed the layers of rock upwards. Ridges of rock bent and broke, leaving behind the ranges seen today. This same action also caused volcanic activity, sending molten lava into but not through the sedimentary rock. While there are no volcanoes in the park, towers of heated rock called igneous batholiths were sent upwards, pushing the sediment further up. The top layer of sedimentary rock was eventually eroded away, resulting in granite towers that form the Ragged Range.

Over the last 2 million years, glaciers have covered most of North America, creating most of the land formations seen today. While previous ice ages affected the Park area, the most recent, the Wisconsin Ice Age (85,000-10,000 years ago) touched only the most western and eastern parts of the Park. This has left many geological features in the park much more time to develop than most of North America had.

The central feature of the park is the South Nahanni River which runs the length of the park, beginning near Moose Ponds and ending when it meets the Liard river near Nahanni Butte. The South Nahanni is a rare example of an antecedent river. The mountains rose slowly enough, and the river was powerful enough that the river maintained its course over its history, meaning it has the same path today as it did before the mountains rose. As the river was meandering, the canyons it carved also meander. Most visitors only visit the portions from Virginia Falls down.

There are four main canyons that line the south Nahanni river, named by prospectors, numbering them as they travelled up the river. The fourth canyon begins with Virginia Falls, and was created as the falls eroded the limestone surrounding the river, working its way upstream. It is five miles long. Third canyon runs through Funeral Range, around 40 km long. Because its walls are composed of a stratum of shale, sandstones and limestone this canyon has long slopes instead of steep, flat walls like the lower canyons. Big bend, a point where the river does a 45 degree turn, marks the end of Third and the beginning of Second Canyon. At 15 km long, it runs through the Headless Range. The final canyon is considered the most beautiful. Beginning after Deadman Valley, First Canyon boasts the highest, most vertical walls, cutting through very resistant limestone. It ends near Kraus Hotsprings, making it about 30 km long. Following this, the river slows and braids into different channels, passing through the Park boundary, and coming together again near the village of Nahanni Butte. Soon after the town, the South Nahanni River joins the Liard river.