Complex sentence: The cause of this significant age change is because the Anahim Volcanic Belt has its origins from the North American Plate moving over the hypothesized Anahim hotspot, a mantle plume that is likely responsible for volcanism throughout the Anahim Volcanic Belt.
Split into simpler sentences: The cause of this significant age change is because the Anahim Volcanic Belt has its origins from the North American Plate moving over the hypothesized Anahim hotspot. This is a mantle plume that is likely responsible for volcanism throughout the Anahim Volcanic Belt.