is truly a "hotspot", and lacking any supporting evidence this putative hotspot track is entirely speculative. The 1983 paper also suggested that passage of a hot spot weakens the continental crust, leaving it vulnerable to rifting. But might the relation actually run the other way: do some of these "hotspots" accumulate in zones where the crust is already weakened (by means as yet unknown)? The supposed Newberry hotspot track may exemplify this (see Megashears, below), but application of this concept more generally is not yet accepted. Application to the OWL would require resolving some other questions, such as how traces of a ca. 150 Ma event resisted being swept north into Alaska to influence a structure believed to be no older than 41 Ma (see Straight Creek Fault). Possibly there is some explanation, but geology has not yet found it. Orofino Shear Zone The OWL gets faint, perhaps even terminates, just east of the Oregon—Idaho border where it hits the north-trending Western Idaho Shear Zone (WISZ), a nearly vertical tectonic boundary between the accreted oceanic terranes to the west and the plutonic and metamorphic rock of the North American craton (the ancient continental core) to the east. From the Mesozoic till about 90 Ma (mid-Cretaceous) this was the western margin of the North American continent, into which various off-shore terranes were crashing into and then sliding to the north. Near the town of Orofino (just east of Lewiston, Idaho) something curious happens: the craton margin makes a sharp right-angle bend to the west. What actually happens is the truncation of the WISZ by the WNW-trending Orofino Shear Zone (OSZ), which can be traced west roughly parallel with the OWL until it disappears below the Columbia River Basalts, and southeast across Idaho and possibly beyond. The truncation occurred between 90 and 70 Ma ago, possibly due to the docking of the Insular super-terrane (now the coast of British Columbia). This was a major left-lateral transform fault, with the northern continuation of the WISZ believed to be one of the faults in the North Cascades. A similar offset is seen between the Canadian Rocky Mountains in British Columbia and the American Rocky Mountains in southern Idaho and western Wyoming. Then another curious thing happens: before the west-trending craton margin turns north, it seems to loop south towards Walla Walla (near the Oregon border) and the Wallula Gap (see orange-line here, or dashed-line