Geologic History of The Howe Sound: Three Little-Known Facts

The Coast Mountains have risen upwards of 4km within the past 10-million years.                                About half of this uplift can be accounted for by isostatic equilibrium (as mountains erode, they lose mass and rise). The rest of this uplift may be attributed to general tectonic processes as well as thermal expansion of the crust due to being along a subduction zone.

Mt. Garibaldi was built by violent volcanic eruptions

15 to 20 thousand years ago the Squamish Valley was filled with a large glacier. Volcanic debris that formed the western slope of the volcano spread across the surface of the glacier. When the glacier later melted, the western side of the volcano collapsed into the Squamish Valley.

The Black Dyke was formed by intrusion of magma along an ancient fracture in the granite of the Chief The intrusion is hypothesized to be a result of magma pushing to the surface of an ancient volcano which has long since eroded away.  Geologists estimate the granite and dyke to be 95 and 30 million years old.