Albor Tholus
Albor Tholus is an extinct volcano in the Elysium Planitia area on Mars. It lies south of the neighbouring volcanoes Elysium Mons and Hecates Tholus. Albor Tholus is 4.5 kilometres high and has a diameter of 160 km at its base. Its caldera has a diameter of 30 km and is 3 km deep. Compared with terrestrial volcanoes the caldera is unusually deep. Evaluations by the Mars probe Mars Express found that the volcanoes of the Elysium region were active over long periods.