Activity of the carbonatite volcano Oldoinyo Lengai, 1966

Abstract

From 1960 to August, 1966, the activity of Oldoinyo Lengai took the form of quiet extrusion of carbonatite lava. In August, 1966, the style of activity changed abruptly and violent ash eruptions took place. The activity varied from minor emissions of ash to major Plinian and Vulcanian type eruptions. A new ash-cone built up within the crater and ash was widely distributed on the slopes of the volcano and over the surrounding countryside.The ash consists of sodium carbonate mixed with crystals of nepheline, pyroxene, wollastonite, apatite, melanite and pyrite. Also blocks of ijolite and melteigite were ejected during the activity.

Melilite-group minerals at Oldoinyo Lengai, Tanzania

“…In historical times several explosive eruptions interrupted the natrocarbonatite effusive activity, erupting mixed silicate-carbonate ashes (Dawson et al, 1968(Dawson et al, , 1992 and carbonated silicate ashes and lapilli, as in the recent activity phase from September 4th of 2007 through the early summer of 2008 (Mitchell and Dawson, 2007;Vaughan et al, 2008;Reusser and Mattsson, 2008;Keller and Klaudius, 2008;Keller et al, 2010).…”

Assessing Performance of the RSTVOLC Multi-Temporal Algorithm in Detecting Subtle Hot Spots at Oldoinyo Lengai (Tanzania, Africa) for Comparison with MODLEN

“…Hot spots detected by MODLEN have been shown to generally match with eruptive activity, witnessed at OL [28]. When observations were available, they proved to be essential data to constrain the changes and variation in eruptive activity from 2000 to 2008 [31,32,46].…”

“…During late March and early April 2006, a vigorous effusive eruption occurred. A lava flow with exceptionally large volume (9 × 10 5 m 3 ; [31]) was emitted in two phases and was emplaced along the western flank, reaching a length of 3 km (see [31]). After approximately one year of quiescence, a new lava emission occurred in July and August 2007, from several vents opening within the crater.…”

“…This remote volcano is the only volcano on Earth emitting natrocarbonatite lava that shows a very low level of viscosity (10 −1 to 10 2 Pa s [29]), and a relatively low temperature (ranging from 495-590 °C), compared to other types of lavas [30,31]. The eruption rates at Oldoinyo Lengai (OL) are extremely low; therefore, lava covers only a few tens of m 2 compared to several hectares or km 2 at other active volcanoes.…”

“…Due to the limited area and temperature of active lava flows, the OL thermal activity is generally difficult to investigate by satellite. A specific adaption of MODVOLC, named MODLEN, has been designed, tailored and tested with good results for better identifying subtle hot spots at OL [30][31][32][33]. This is not routinely monitored by ground-based systems, as is similar with other African volcanoes [34].…”