Where mountains once stood.

Where mountains once stood

Wind and water can gradually remove almost all signs of once-splendid mountain peaks. But erosion cannot erase everything. Often, the roots of ancient mountains survive beneath what looks like unimpressive landscape. Using such buried evidence, a group of researchers has identified the remains of a previously unknown mountain belt that stretched over 1,000 kilometers across northwest Canada.

Frederick A. Cook and his colleagues from the University of Calgary in Alberta discovered these roots primarily from seismic profiles recently released by oil companies. Using seismic waves almost like a radar, geophysicists can identify structures in underground rock. Profiles for the region between Canada's Great Bear Lake and the Beaufort Sea show that huge faults and folds run through the basement rock. These structures indicate that long ago, tectonic forces from the east and west squeezed the crust, causing mountains to grow along a north-south line. Similar folds and faults form the roots of the modern Appalachians and Rocky Mountains, says Cook.

The researchers cannot pinpoint when the mountain belt grew, but evidence suggests it happened sometime between 1.2 billion and 0.9 billion years ago. Cook says a collision between North America and another, unknown land mass created the tremendous forces that raised the mountain belt.