In some places, old rocks have been pushed up over younger ones. Generally, there is a tendency for the south west slopes to be gentle, the north east ones to be steep or even cliff-like, resulting in grand scenery. This is fossil country, such as the World Heritage site at the Burgess shale beds near Field. The Alberta Plains is a sedimentary basin that intrudes into the north eastern corner of the province, on the east side of the Rocky Mountains. Drained by the Peace River, sediments here are thousands of metres thick, and are known best for their oil and gas production.
Granite is a typical intrusive rock, being coarse grained.
It cooled slowly deep down, allowing feldspar, quartz and usually mica and hornblende to crystallize in the rock matrix. Igneous rocks can be extrusive too, which means they reached the surface as lava or magma flows and cooled quickly, to form fine grained material. Basalt and rhyolite have much the same chemistry as granite but, by cooling more quickly, do not allow crystals to form. When rhyolite is blown by hot gases into a sponge texture, it is called pumice, which is a volcanic froth. There are pumice deposits NW of Pemberton.