Nature
The Pyramid Formation is an early Pleistocene stratigraphic unit in northwestern British Columbia within the Mount Edziza volcanic complex, named for The Pyramid lava dome on Mount Edziza’s northeastern flank. It consists of a basal pyroclastic member, deposited by a surge and containing trachytic pumice, sodic pyroxene, and alkali feldspar, overlain by a much thicker basalt member made of several flows emplaced soon afterward. Later silicic lava domes and minor flows, including Sphinx Dome, Pharaoh Dome, and The Pyramid, formed after the basalt. With an estimated volume of 11.4 cubic kilometres, it preserves a sequence of explosive and effusive volcanism within this major volcanic region.
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British Columbia · Canada