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 fireplace may be better used instead. These are designed to contain the entire fire instead of just keeping it in one place. A fire ring may be nothing more than a short, wide section of metal tube, partially buried in the ground. Slightly more advanced fire rings may be partially covered with metal bars so that the fire may be used for cooking. These types are seen at many campgrounds. Fire rings in urban areas, such as on beaches, may be made of poured concrete. Makeshift fire rings can be constructed out of a ring of stones where pre-constructed rings