The rocks within the ranges were formed by volcanic activity between ~1595-1592 Ma, when the Gawler Range Volcanics were erupted. Approximately 30 000km³ of dominantly rhyolitic and dacitic lava were rapidly extruded, and their eroded remnants preserve one of the most voluminous felsic magmatic events preserved on earth. Basaltic and basaltic-andesite comprise a remarkably minor component of the magmatism (<1%). The Gawler Ranges Volcanics were also erupted at remarkably high temperatures (~950-1100°C) for felsic magmas, and this, coupled with their very high halogen (particularly F and Cl) compositions resulted in highly viscous (runny) magmas when compared to typical rhyolites and dacites which are generally several hundred degrees cooler. This high viscosity resulted in emplacement as a series of lobate flows with a stacked pancake-like morphology which cooled rapidly resulting in porphyritic textures and widespread columnar jointing.The ranges are a small part of the Gawler Craton which is a craton rich in mineral resources, although many are only recently discovered and not yet fully exploited.