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Central portion of regional cross section through the Southern Cordillera.

Those are the "antiforms" shown on the cross section, like the Nicola and Vernon antiforms. These subsurface structures are mighty high, with a covered relief of up to 25 km and a lateral extent of 100 km.

Throughout, large strike-slip faults (like the San Andreas fault in California), sliced up the crust and carried parts of it as far north as Alaska. The most recent one is the Queen Charlotte fault (mentioned earlier) but older ones sliced much of British Columbia and the Yukon, emphasizing the north-south belts of the Cordillera as seen on a previous slide (#53).
The long crustal cross-section shown in the brochure folder cuts across the belts and extends westward across the subduction zone and out to the Juan de Fuca ridge where, today, submarine outpourings of basalt magma continue to form new lithosphere of the Pacific plate to the west and the Juan de Fuca plate to the east. Here are the major points again:

The cross section chronicles a voyage of discovery, from Alberta to west of Vancouver Island, along an 1,100-km-long, deep cut through stacked, twisted, displaced, reworked and remolded rocks and formations.

The Canadian Shield (mottled red), i.e. our old Precambrian craton, doesn't end with the Alberta Basement. We can follow the basement right under the mountains and on westward at least to below Okanagan Lake.

In central British Columbia, between Kootenay Lake and the Fraser River, the features showing the most vertical relief lie buried: they occur as a series of huge underground arches, up to 25 km high. Mt. Everest could easily fit inside them.

Geophysicists subdivide our lithosphere into an upper and a lower part, crust and mantle (continental mantle is shown in purple; oceanic mantle in grey), separated by the Mohorovicic discontinuity or Moho, below which seismic responses differ from those above it. Observe how steady the Moho is! Given the changing surface topography from the Rockies to the Strait of Georgia, one also may have expected some changes in the base of the crust, which is the Moho. Not so!
The Moho is remarkably flat. This is a fundamental discovery. It means that mountain belts, resulting from collisions, were formed above this flat base, perhaps as a rug wrinkles when pushed about a flat floor.

The explanation is that the rocks below the Moho possess qualities which differ from those above, including a higher density and great strength. And just try to imagine the forces which did the wrinkling above the Moho, and stacked up the Rockies!.

Under the west coast, our seismic x-rays have revealed a complex, geological structure beneath the Coast Mountains. It is an intricate pattern representing older shingling and wedging rock plates which were imbricated when continental and oceanic plates collided and also caused the ascent of magma from frictional and other heating, forming all the granite rocks of the Coast Mountains and, of course, volcanoes such as Mt. Garibaldi.

Beneath Vancouver Island and offshore, the collision continues today. We can "see" from our remote images how the lithosphere of the Juan de Fuca plate, moving eastward, is subducting beneath the North American plate, which is moving westward. We have been able to follow the subducted plate deep (70 km) beneath the mainland on the east side of the Strait of Georgia. We also know from chemical studies of the volcanic rocks that they formed from parts of this subducted plate, melted at depths of 100 km and more.
Well, there we are. This completes our sweeping investigation of the continent and its growth, down to its very roots and back to its beginnings. We have travelled through longer than four billion years in just, well how many hours?

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