Geology of Strathcona Park - Plate Tectonics

Plate Tectonics

The Earth's surface is not a static unchanging place. In addition to the observable processes happening around us, the crust below our feet is continually moving and being formed and destroyed.

The Earth's crust is a relatively thin skin floating on top of the more fluid, and hot dense mantle rocks beneath. There are two types of crust; oceanic crust, around 6 kilometres thick and composed of basaltic lava, and continental crust, up to 35 kilometres thick and composed of granitic and sedimentary rocks. The crust is divided into many irregular shaped plates which move around in response to convection currents within the mantle. These plates can meet in three ways:

spreading ridges - are crustal growth zones where the crust is moving apart and new oceanic crust forms. This is occurring along the mid-Atlantic ridge as America and Europe move farther apart. It is also occurring along several ridges, e.g., the Juan de Fuca Ridge, which occurs just a few hundred kilometers off the west coast of British Columbia.
subduction zones - are destructive zones where oceanic crust is forced down into the mantle as two plates converge. This is happening beneath British Columbia as the Juan de Fuca Plate is forced beneath the North American Plate.
transform faults - where two plates are sliding past one another. The San Andreas fault in California is of this type.

All three of these situations are present today off Canada's geologically complex west coast. All three have played their part in creating Strathcona Park and bringing it to its present location.

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