In non-geologic terms, the Teton Range is just a youngster that’s still growing.
Part of that growth is a prominent fault line that sits along the eastern base of the range. In an effort to study and track the fault line, the Wyoming State Geological Survey recently published a new map depicting the Teton fault. The map is available for a free download at tinyurl.com/teton-fault-map, or it can be purchased in poster form.
The map is the result of a group effort by state, federal, academic and consulting geologists. The lead author of the map is Mark Zellman of BGC Engineering, a geologic firm.
Zellman said the map was created using a high-resolution remote sensing data called light detection and ranging to create a detailed image of the ground surface and map the fault from a passing airplane. For this map, the detection equipment showed fault locations in greater detail than previous maps, which were limited by dense vegetation and rugged terrain.
“The new fault map represents a state-of-the-art understanding of the Teton fault’s length and location,” Zellman said.
Although the fault line represents the potential for earthquakes, Zellman said changes come generally in tiny increments. He and other geologists have recently been studying prehistoric earthquakes to “try to understand when large earthquakes have occurred on this fault.”
He said the last major earthquake along the fault line occurred 4,500 to 8,000 years ago. “The time between measurable events is measured in thousands of years,” Zellman said.
“The map and associated paleoseismic work has significantly increased our understanding of the Teton fault and potential hazards,” Wyoming State Geologist Erin Campbell said in a news release. “This fault accommodated more than 30,000 feet of uplift, documented by measuring the change in elevation from the Cambrian-age sandstone at the top of Mount Moran to the depth of that same rock in the subsurface of Jackson Hole.”
Zellman said along the fault line the mountains are getting taller and the valley (Jackson Hole) is getting lower. But don’t expect to notice. Zellman said it’s measured in .8 millimeters per year. A growth spurt might be 2 or 3 millimeters a year. That’s 300 years or so to grow a foot.
Zellman says so far the map has been well received.
“A lot of people have been using the map as wall decorations,” he said. “It’s an informational poster. Using it to update (geologist’s) national seismic hazard maps. ... People are using it to plan future research on the fault and general science communication as to where is the fault.”