sentences:  Heavy mineral deposits containing iron had collected on the shores of the receding sea to form the Mesabi, Cuyuna, Vermilion, and Gunflint iron ranges from the center of the state north into Northwestern Ontario, Canada.These regions also showed the first signs of life as algae grew in the shallow waters.Over 1,100 mya, a rift formed and lava emerged from cracks along the edges of the rift valley.