Alaska-Yukon Cruise Tour

Tintina Trench

The Tintina Trench is one of western North America’s most important physical features, visible even from the moon. It is a straight valley over 1500 km long that extends southeast from Alaska, across the central Yukon and continues into British Columbia. The valley overlies a fault line that is part of a global system of faults that break the earth’s outer shell into a mosaic of giant plates. It is the movement of these plates - toward, away from or parallel to each other - that produces geological phenomena like earthquakes and volcanoes. Between 55 million years ago and 40 million years ago plate movements shifted the rocks on either side of the Trench in opposite lateral directions, displacing the rocks on the southwest edge of the trench more than 400 km to the northwest.

Tintina Fault

The long, linear depression that extends northwesterly across the Yukon from Watson Lake along to Ross River, Faro and Dawson, and then into Alaska is the Tintina Trench. It is the northern continuation of the Northern Rocky Mountain Trench in British Columbia. The Tintina Trench is the physiographic expression of the Tintina Fault. Tectonic forces caused the block of rocks southwest of the fault to grind up against the stable North American block and, during a history of innumerable earthquakes, moved the southwestern block northwest towards Alaska. The grinding along the fault caused the rock to break up and become less resistant which, with erosion led to the formation of the trench. Most geological evidence suggests that there was at least 450 km of right-lateral displacement (area southwest of the fault moved northwest) along the Tintina Fault although there may have been as much as 1200 km offset. Volcanic rocks were deposited in the trench about 55 million years ago - probably at the same time as some of the motion along the Tintina Fault. These volcanic rocks host the Grew Creek gold deposit.

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