VOLCANIC FLOW DEVELOPMENT AT ALBA-PATERA, MARS

The Hesperian-Amazonian age volcanic shield, Alba Patera, has associated with it some of the largest volcanic flows on Mars. An early (Hesperian) flood-lava phase was followed by the extrusion of high-volume sheet and tube-fed lavas, many of which emerged from fissures on the flanks of a rising dome. Subsequently a plethora of sheet and tube-fed lavas were erupted from linear vents located either at or within 200 km of the present summit. These built complex flow fields which were erupted at rates several orders of magnitude greater than the maximum Hawaiian rates. Later (Amazonian) volcanism at Alba saw extrusions of long, narrow flows from two complex summit calderas whose formation is inferred to have been a direct result of magma supply to the volcano's flanks. The outflow of thermal energy related to emplacement of some single flows (6 × 1028 ergs) was substantially greater than Earth's annual heat loss through volcanism and implies that patera building that have been a significant source of geologically rapid heat loss from Mars during the early stages of volcanic centralization on the planet. © 1990.