Posted on behalf of Alexandra Witze.
The walls of the Geological Survey of Canada’s Vancouver office are, not surprisingly, plastered with maps. There’s one of the country of Canada, one of the province of British Columbia, and even a circumpolar Arctic map centered on the North Pole.
The Klondike schist of Canada (shown in green) stops at the border with the United States. {credit}Alexandra Witze{/credit}
All display that distinctive rainbow mélange so typical of professional geologic maps. Each major rock formation is represented by its own colour, so that pinks and purples and yellows swirl in great stretches representing mountain ranges, coastal plains, and every conceivable landscape in between.
But lying on the table of the survey’s main conference room is a much more problematic map. It shows part of the far northern boundary between the United States and Canada, along a stretch between Alaska and the Yukon territory. And the two sides, on either side of the international border, do not match.
It’s not a question of Canada using one set of colours for its map and the United States using another. The geology simply does not line up. To the east, Canadian mappers have sketched a formation called the Klondike schist, which is associated with the gold-rich rocks that fueled the Klondike gold rush in the late 1890s. To the west, US maps show nothing like it.
“We don’t know why,” says Jamey Jones, a geologist with the US Geological Survey (USGS) in Anchorage, Alaska. “We have got to figure out why these aren’t matching.”
He and two dozen scientists from both sides of the border — but clad equally in plaid shirts and hiking boots — met in Vancouver on 20 October to try to hammer out the discrepancies. For two hours they compared mapping strategies, laid out who needed to explore what next, and swapped tips about the best ways to get helicopters in the region.
The last frontier
At one level, the differing maps are a relatively minor academic point to sort out. Such glitches are fairly common whenever geologists have to match one ‘quadrangle’ mapped from one era or with one technique against another from a different time. And it’s not unusual for geology to not quite line up across international borders.
But American and Canadian geologists have reconciled their maps along nearly the entire northern stretch where Alaska and the Yukon meet, says Frederic “Ric” Wilson, a geologist with the USGS in Anchorage. This last bit is the only one that does not match — and it may well be because the Canadian maps are four years old, while the American ones are four decades old.
The US maps stretch back to the days of legendary geologist Helen Foster, who mapped large parts of Alaska after making her name as a post-war military geologist in former Japanese territories. “With her, you walked every single ridge,” recalls Wilson. “Every single ridge.”
All that walking produced maps of huge stretches of the remote Alaskan landscape. They include the 1970 quadrangle map now in question, which abuts a much newer Canadian quadrangle to the east. Together the maps span part of a massive geological feature known as the Yukon-Tanana Terrane, a collection of rocks caught up in the mighty smearing crush where the Pacific crustal plate collides against North America.
The Canadian side of the map is in good shape. Prompted in part by intense mining interest, geologists there have mapped the Klondike in modern detail. “I’m willing to integrate any piece of data that comes in,” says Mo Colpron, a geologist with the Yukon Geological Survey. “If you guys come up with things that affect how our side of the border works, then we can sit down and talk and try to mesh it.”
That leaves the burden of work on the US side, to update the Foster maps. “The reconciliation project is what it’s called,” says Rick Saltus, a geologist with the USGS in Denver, Colorado, who served as meeting emcee. “We’re taking a three-year look at cross-border tectonic connections, because things look a little different from one side to the other.”
This summer, Jones and his colleagues hired a helicopter to take them everywhere the Foster maps ran up against the Klondike formation. “We’ve seen a lot of rocks we didn’t anticipate seeing,” he says. That data will go into the new and improved US maps.
There is, however, only so much scientists can do. Citing border regulations, Jones says, the helicopter pilot was unwilling to take them just a tiny bit over into Canada so they could see the geology on the Yukon side.
