Geologic Activity

Gable Mountain, part of the Lewis Range, is located in the far northeast corner of the park.

NPS photo.

Glacier National Park is defined by geological processes that have been occurring for millions of years, beginning with the deposition of the Belt Sea (1,600 million years ago) and continuing with more recent periods of mountain uplift and glaciation. Geologic activity continues to reshape the park landscape, albeit in more subtle ways such as:

• Landslides

• Heavy spring snowmelts

• Earthquakes

 

A spring slide at Weeping Wall. Glacier's Road Crew knows all too well the power and frequency of geologic events.

NPS photo.

Landslides

Numerous landslides have occurred throughout Glacier in recent years, influenced by landform and climate. A large landslide was recorded on Chief Mountain in 1992. The east side of the park, in particular, is characterized by loose soils prone to periodic movement down steep slopes. The freeze/thaw cycle of changing seasons greatly influences landslide events.

 

Stream channels and their effects on the park's geology can be seen in many places within the park. The Trail of the Cedars shows the Avalanche Gorge and other examples of the associated runoff from spring snowmelts.

NPS photo by Tim Rains.

Heavy Spring Snowmelts

Heavy spring snowmelts, and associated runoff in park streams, contribute to the movement of rock material and the relentless meandering of stream channels. Eroded rock material is flushed down steep mountain streams in the spring and re-deposited in gentler sections downstream, where new stream channels are created through the scouring forces of water and rock. Riparian zones and floodplains along creeks and rivers are in constant change as a result of this annual process. The North Fork of the Flathead River and its tributaries are good examples.

 

The Lewis Mountain Range we see today was partially formed by the Lewis Thrust Fault. The fault follows the eastern range front, near the east boundary of the park.

NPS photo.

Earthquakes

Many faults run through the park, creating the potential for earthquakes. However, compared to other areas of the western United States, earthquake activity is infrequent and usually minor. Southwest Montana has greater seismic potential compared to the northwest region, where Glacier is located.