The volcanic rocks of the Plateau of Santa Catarina are constituted, predominantly, by spills of basaltic and andesito-basaltic composition. Rocks of intermediate composition occur in the central-west region and were classified as porphyritic granophytic porphyritic. Acidic rocks are represented by granophytic hemicrystalline dacites in the southeast region and by granophyllic rhyolites in the central-west region, towards the State of Paraná. Magmatic activity in the upper mantle and the lower crust during the Cretaceous was responsible for this diversity of petrographic types. The determination of the density of the rocks gave significantly different values, constituting a sensitive parameter for the distinction between them.
