This seismic cross section gives you a coherent,
underground picture of the gigantic thrusting which built the Grenville
Orogen. Think of it as a gigantic X-ray (or even better an ultra-sound)
picture. The outcrop we just saw is but a tiny sliver within this
package of many rock units, which contains many tens of kilometers
of cumulative thickness. The tectonic push came from the right of
the cross section.