Ngauruhoe (7,500 ft) has an almost perfect cone rising 3,000 ft above the southern slopes of Tongariro. It has been the most continuously active of New Zealand volcanoes in the recent past. Eruptions from this mountain were regarded by the Maori as a sign of war. Except on the east, young lava flows have reached their base on all sides and these have a loose, rugged, clinkery surface. Since 1839 considerable changes have occurred within the crater. The more notable eruptions were in 1841 with ash eruption which truncated the top, in 1855 when the west side of the crater wall collapsed, in 1859 when the east wall of the crater collapsed, in 1870 with ash eruption and lava flow, in 1949 with ash eruption and lava flow, and in 1954–55 again with ash eruption and lava flow.