significant differences of geology. These are much too correlated to be dismissed as random alignments. But for all of its prominence, there is as yet no understanding of what the OWL is or how it came to be. The OWL piques the interest of geologically minded persons in part because its characteristic NW-SE angle of orientation – approximately 50 to 60 degrees west of north (a little short of northwest) – is shared by many other seeming local features across a broad swath of geography. Around Seattle these include strikingly parallel alignments at the south end of Lake Washington, the north side of Elliott Bay, the valley of the Ship Canal, the bluff along Interlaken Blvd. (aligned with the Ship Canal, but offset slightly to the north), the alignment of Ravenna Creek (draining Green Lake southeast into Union Bay) and Carkeek Creek (northwest into Puget Sound), various stream drainages around Lake Forest Park (north end of Lake Washington), and (on the Eastside) the Northrup Valley (Hwy. 520 from Yarrow Bay to the Overlake area), and various smaller details too numerous to mention. All of these are carved into "recent" (less than 18,000 years old) glacial deposits, and it is difficult to conceive of how these could be controlled by anything other than a recent glacial process. Yet the same orientation shows up in the Brothers, Eugene-Denio, and McLoughlin fault zones in Oregon (see map, below), which are geological features tens of millions of years old, and the Walker Lane lineament in Nevada. Likewise to the east, where both the OWL and the Brothers Fault Zone become less distinct in Idaho where they hit the old North American continental craton and the track of Yellowstone hotspot. But some 50 miles to the north is the parallel Trans-Idaho Discontinuity, and further north, the Osburn fault (Lewis and Clark line) running roughly from Missoula to Spokane. And aeromagnetic and gravitational anomaly surveys suggest extension into the interior of the continent. Structural relationships with other features A problem in evaluating any hypothesis regarding the OWL is a dearth of evidence. Raisz suggested that the OWL might be a "transcurrent fault" (long strike-slip faults at what are now known to be plate boundaries), but lacked both data and competence to assess it. One of the first speculations that the OWL might be a major geological structure – written when the theory of plate tectonics was