1.5 billion years ago Missouri was a vast area of explosive volcanism. Volcanoes and fissures spewed forth upon the earth’s surface thick layers of fast cooling rhyolite lava, volcanic ash, and volcanic fragments. This material can be seen today as hard, blocky rocks in road cuts and on Taum Sauk Mountain about 80 miles South of St. Louis. At Longview Farm Park rhyolites lie about 2800 feet beneath the surface.
Some very primitive life forms lived in lakes that dotted the volcanic region. They were a form of algae that left structures called stromatolites and they are evidence of the earliest forms of life in this part of the country.