The Mount Edziza volcanic complex began forming about 7.5 million years ago and has grown steadily since then. Like other volcanoes in northwestern British Columbia, the Mount Edziza volcanic complex has its origins in continental rifting—a long divergent plate boundary where the lithosphere is being pulled apart. Here, the continental crust of the North American Plate is being stretched at a rate of about per year. This incipient rifting has formed as a result of the Pacific Plate sliding northward along the Queen Charlotte Fault, on its way to the Aleutian Trench, which extends along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula. As the continental crust stretches, the near-surface rocks fracture along steeply dipping cracks parallel to the rift known as faults. Hot basaltic magma rises along these fractures to create passive lava eruptions, known as effusive eruptions.