Heard Island, by far the largest of the group, is a mountainous island covered by 41 glaciers (the island is 80% covered with ice) and dominated by the Big Ben massif. It has a maximum elevation of at Mawson Peak, the historically active volcanic summit of Big Ben. A July 2000 satellite image from the University of Hawaii's Institute of Geophysics and Planetology (HIGP) Thermal Alert Team showed an active and 50- to 90-metre-wide (164–295 ft) lava flow trending south-west from the summit of Big Ben.