Photos: Landslide vs. glacier in heart of Alaska

A landslide from an unnamed 7,000-foot peak covered Black Rapids Glacier after the 2002 Denali Fault Earthquake.
Dennis Trabant | USGS
Geologists examine large cracks in the ground formed by the 2002 magnitude 7.9 Denali fault earthquake, which was strongly felt in Fairbanks and Anchorage.
USGS / Peter Haeussler
Seismic waves from the Cook Inlet earthquake propagate over 74 seconds, with intensified shaking in the sedimentary basin, as seen in Tape’s model.
Courtesy Carl Tape
Mike Campbell

It’s been more than a decade since the large 7.9-magnitude Denali Fault Earthquake rocked Interior Alaska, but fascinating images continue to pop up from time to time.

We love this intersection of primal geologic forces presented in this photo -- the Black Rapids Glacier, a glacier known to surge from time to time, and an earthquake-triggered landslide from a nearby 7,000-foot peak. According to the U.S. Geologic Survey, “three rock falls from the south wall of the Black Rapids Glacier covered about ... 5 percent of the total glacial area."

The big quake struck Nov. 3, 2002, rupturing the surface of the Earth for 209 miles along the Susitna Glacier, Denali and Totschunda fault lines. Because it shook a sparsely populated area in Alaska, the massive quake didn’t kill anyone or cause major damage, although the runway at  the airport of Northway, population 71, was badly damaged. Denali Fault-induced landslides may have numbered in the thousands, clustered in a narrow band extending no more than 12 miles on either size of the fault line.

The big shaker also provided some evidence that the 800-mile trans-Alaska oil pipeline was well constructed. Although the Denali Fault shifted about 14 feet beneath the pipeline, the line, which currently carries more than a half-million barrels of crude per day, didn’t rupture.

The Denali Fault event may have been triggered by a magnitude-6.7 quake that occurred nearby 10 days earlier. Called the Nenana Mountain earthquake, the smaller event caused only limited damage. By contrast, the 1994 Northridge, Calif., temblor, which had the same magnitude as the Nenana Mountain shaker, caused 67 deaths and $40 billion in damage when it struck densely populated Los Angeles.

During the 10 days following the Denali Fault earthquake, geologists from the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys -- as well as several universities -- mapped and measured the earthquake rupture on the ground and using aircraft. They also located major landslides caused by the quake.