GPLATES puts this massive database of western US volcanism in motion and in perspective. The results are very interesting. Supposed contact with the Insular Terrain/Wrangellia/Baja BC does not show much increase in volcanic activity. Neither does the proposed entourage of buoyant plateaux led by a supposed Shatsky conjugate.

Insular super terrain approaches 105 Ma. Shatsky conjugate approaching lower left (yellow). From Wu-Clennet TOMOPAC 90 features.

99 Ma Insular terrain contacts and begins moving north without noticeable increase in vulcanism.

91 Ma Shatsky conjugate hits and Insular terrain slides north. Still not much volcanic increase.

80 Ma Shatsky conjugate penetrates through Wyoming. Orange colored volcanics along the coast in this interval are Sierra and Peninsular Ranges arc magmatism expected at this time regardless of oceanic plateaux. Navdat does not correct for Great Basin extension so these apparently offshore features must be mentally moved inland. The yellow arrow and path is for an alternate conjugate departure point further north and west in the Pacific favored by the Earthbyte group.

76 Ma Papanin conjugate like a tail on Shatsky starts dragging across with little effect. Alternate path approaches coast to north. White dots to left are Yellowstone hotspot depth slices with surface (not yet reached) furthest north.

60 Ma. Neither the entire entourage of conjugates nor the path alternate shows much increase. Yellowstone Hotspot surface location now has a yellow circle. Some arc volcanics (orange) crop up in the Peninsular ranges (Baja).

Slide 1 again for comparison.

48 Ma Siletzia begins docking and volcanics pop up inland.

35 Ma. We zoom in now to watch the Yellowstone hotspot surface location (yellow small circle) track south of McDermitt (white small circle) and watch volcanics sweep from Idaho down into Nevada.

15 Ma. Yellowstone Hotspot surface location (yellow circle) is well up the eastern Snake River plain without leaving much of a track.

0 Ma. Zoomed back out to see Yellowstone Plume in its current location and the western US filled in with increasingly mafic volcanics.

This exercise casts doubt on the role of oceanic plateaus and establishes the docking of Siletzia and attendant clockwise rotation of the Pacific Northwest, along with the northward subduction of the East Pacific Rise; as the major drivers of volcanism in the western US.