BUILDING VANCOUVER: DIVERSE BEDROCK

Vancouver sits at the western edge of British Columbia. It is famous for its mix of mountain, rain forest, ocean shore and urban life.

When you think of Vancouver, you picture Stanley Park, the iconic north shore mountains, pristine waters caressing beautiful beaches from the Seawall all the way round to Kitsilano and Spanish Banks.

This landscape is carved from a bedrock collage of different rock types, each with a unique geological history and landscape form.

Geologists distinguish five major rock types in the Vancouver area. The most extensive are: (1) granitic and (2) metamorphic rocks of the Coast and Cascade Mountains. Overlying these within the Fraser Valley is a thick sequence of (3) sedimentary rock (sandstone and shale).

Volcanic intrusions (4) fill fractures within granitic, metamorphic and sedimentary rocks. Younger volcanic rocks (5) make up volcanoes built on older granitic and metamorphic rocks.

Each rock type is an aggregate of minerals. The different colour, texture, hardness, porosity and chemistry of each rock type reflects the different type, shape and size of their mineral constituents.

Where Rocks are Made: the Tectonic Kitchen

Rocks are forming today in a great tectonic 'kitchen' below southwestern BC. Fueled by heat from the earth's interior and collision between continental North America and the undersliding oceanic plate, this kitchen produces a variety of rock types along with earthquakes and rising mountains. 

Sediment eroded from mountains accumulates in basins such as the Strait of Georgia and converts with deep burial to sedimentary rocks. 

Forces of tectonic collision deform deep crustal rocks into new metamorphic rocks. Melted rocks cool to form bodies of igneous granitic rocks. Where these rock melts rise to the surface, volcanoes are built. Ongoing uplift and erosion of mountains over time bring deeply buried rocks to the surface.

References:

CGEN Archive: https://www.cgenarchive.org/vancouver-rocks.html#:~:text=Geologists%20distinguish%20five%20major%20rock,rock%20(sandstone%20and%20shale).&text=Each%20rock%20type%20is%20an%20aggregate%20of%20minerals.