Circum-Superior Belt northwestern Superior craton margin intrude an older, 2,090 to 2,070 million-year-old dike swarm. The Ospwagan Group is younger than and the 1,864 million-year-old Winnipegosis komatiite belt lies to the southwest. Numerous tectonic settings have been suggested for triggering magmatism in the Fox River Belt, including a marginal basin rifting event. At the southern portion of the Circum-Superior Belt, a group of fragmental sediments composed of iron formation was formed during a period of magmatic activity in the Marquette Range Supergroup. Included in the Marquette Range Supergroup is the Hemlock Formation, a bimodal volcanic group that is estimated to have an
Fire ring are not available, but care should be taken as some stones can explode when heated due to trapped gas pockets, thermal expansion, or water contained flashing into steam. Fire ring A fire ring is a construction or device used to contain campfires and prevent them from spreading and turning into wildfires. A fire ring is designed to contain a fire that is built directly upon the ground, such as a campfire. Fire rings have no bottom, and are simply circles made of forged metal, stones, concrete, etc. which surround and contain a fire. Manufactured steel fire rings are available in