VOLCANIC GEOLOGY OF TYRRHENA PATERA, MARS

Models derived from the study of terrestrial pyroclastic flows have been applied to the deposits at Tyrrhena Patera and indicate that the distribution and lengths of the observed deposits are consistent with an origin by the emplacement of gravity-driven ash flows generated by hydromagmatic or magmatic explosive eruptions. Tyrrhena Patera represents the earliest central vent volcanism identified on Mars and may reflect a transition from the flood-style eruptions which dominated early Martian history. A hydromagmatic origin for Tyrrhena Patera is in agreement with suggested climatic changes on Mars and may explain the absence of this style of volcanism in later eras. Alternatively, a magmatic origin for Tyrrhena Patera implies an evolution in the types of magmas produced on Mars from Hesperian to Amazonian time, during which the prominent shields in the Tharsis region formed. -from Authors