 The kimberlite pipes of the Mountain Lake cluster were formed during a similar timespan with the Birch Mountains field 77 million years ago.The Canadian portion of the Pacific Northwest began forming during the early Jurassic period when a group of active volcanic islands collided against a pre-existing continental margin and coastline of Western Canada.These volcanic islands, known as the Intermontane Islands by geoscientists, were formed on a pre-existing tectonic plate called the Intermontane Plate about 245 million years ago by subduction of the former Insular Plate to its west during the Triassic period.