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
Ring of Fire (anthology) Ring of Fire (anthology) Ring of Fire is the third published book by editor-author-historian Eric Flint of the 1632 series, an alternate history series begun in the novel "1632" (February 2000). The "Ring of Fire" is both descriptive of the cosmic event as experienced by the series' characters, but also is at times used as the name for the series itself. The series is set in war-torn Europe during the middle of the Thirty Years' War. "Ring of Fire" is a collection of short stories —half by a variety of established science fiction authors invited into the setting, half fan-fiction