On 20 December 1976, a team visited the crater of Mt. Erebus. They reported the continued existence of the anorthoclase phonolite lava lake first discovered in December 1972. During the 4 years of its existence, the lava lake has slowly increased in size and is now ~100 m in diameter. A temperature of 980 ± 20°C was obtained using an optical pyrometer. Vigorous convection occurred over part of the lava lake.

Geological Summary. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. It is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. A summit plateau at about 3,200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater; other lava lakes are sometimes present. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity with minor explosions, punctuated by occasional larger Strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history.

Information Contacts: P. Kyle, Ohio State Univ.