Circum-Superior Belt age of . Another volcanic series in the Marquette Range Supergroup, known as the Gunflint Formation, has an age of . Further geologic units that are related to the Gunflint Formation include the Badwater volcanics and the Kiernan sills. A number of origins have suggested for the Marquette Range Supergroup magmatism. This includes subsidence being driven ahead related to thrusting of the Penokean orogeny or a possible back-arc basin, and lateral flow through the Pickle Crow dikes transported magma from the Fox River Belt area through the Superior craton for placement in the Marquette Range Supergroup. This suggested long-range origin
Earthquake noted, which could be explained by a cyclical pattern of periods of intense tectonic activity, interspersed with longer periods of low-intensity. However, accurate recordings of earthquakes only began in the early 1900s, so it is too early to categorically state that this is the case. Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000 km long, horseshoe-shaped zone called the circum-Pacific seismic belt, known as the Pacific Ring of Fire, which for the most part bounds the Pacific Plate. Massive earthquakes tend to occur along other plate boundaries, too, such as along the