Satellite observation of active carbonatite volcanism at Ol Doinyo Lengai, Tanzania

Oppenheimer, Clive

doi:10.1080/014311698216422

Cited by 16 publications

(12 citation statements)

References 12 publications

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“…Past silicate eruptions from OL have consisted of rocks such as nephelinite, ijolite (nepheline+ augite), and pyroxenite (Oppenheimer, 1998;Klaudius and Keller, 2006). The plume was hypothesized to contain a mixture of Na-carbonate minerals, perhaps hydrated by their exposure to the humid atmosphere (e.g., gaylussite), and silicate minerals that are typical of past explosive eruptions (e.g., nepheline) (Dawson et al, 1968;Dawson et al, 1995;Oppenheimer, 1998;Klaudius and Keller, 2006). Analyses of the TIR data using a decorrelation stretch (DCS) color enhancement (Gillespie et al, 1986), and the spectral emissivity information, were used to examine the composition of different parts of the plume.…”

Section: Ash Plume and Burn Scarsmentioning

confidence: 99%

“…The typical mineralogy of natrocarbonatite lavas from OL includes: Nyerereite (Na 2 Ca(CO 3 ) 2 ), gregoryite (Na 1.2 K 0.6 Ca 0.1 (CO 3 )), sylvite (KCl), and fluorite (CaF 2 ) (Dawson et al, 1990;Keller and Krafft, 1990;Oppenheimer, 1998). However, upon exposure to humid air these minerals hydrate to minerals such as: gaylussite (Na 2 Ca(CO 3 ) 2 5H 2 O), nahcolite (NaHCO 3 ), and pirssonite (Na 2 Ca(CO 3 ) 2 2H 2 O) (Dawson et al, 1987;Keller and Krafft, 1990;Koberski and Keller, 1995;Zaitsev and Keller, 2006).…”

Section: Astermentioning

confidence: 99%

“…It has been the focus of numerous studies due to its uniqueness as it is the only volcano that produces natrocarbonatite lava with very low viscosity (10 − 1 to 10 2 Pa s -compared to 10 2 to 10 4 Pa s for basalt) and low temperature (495-590°C -compared to 700-1200°C for silicate lavas) (Dawson et al, 1968;Krafft and Keller, 1989;Dawson et al, 1990;Wolff, 1994;Pinkerton et al, 1995;Norton and Pinkerton,1997;Oppenheimer,1998). Occasionally OL has exhibited more silicate-rich natrocarbonatite eruptions (i.e., 3% silica instead of b1%), including lava flows in June 1993 and March 2006 (Nyamweru, 1990;Dawson et al, 1994;Pinkerton et al, 1995;Nyamweru, 1997;Oppenheimer, 1998;Klaudius and Keller, 2004;Kervyn et al, in press-a,b). Also, on at least three occasions during the last century (in 1917, 1940-41, and 1966-67) OL produced sub-plinian explosive silicate eruptions resulting in the dispersal of a mixture of silicate and carbonate ash up to 180 km away (Dawson et al, 1968;Nyamweru, 1990;Dawson et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

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Satellite measurements of recent volcanic activity at Oldoinyo Lengai, Tanzania

Vaughan

Kervyn

Realmuto

et al. 2008

Journal of Volcanology and Geothermal Research

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Oldoinyo Lengai (OL) is the only active volcano in the world that produces natrocarbonatite lava. These carbonate-rich lavas are unique in that they have relatively low temperatures (495-590°C) and very low viscosity. OL has been erupting intermittently since 1983, mostly with small lava flows, pools and spatter cones (hornitos) confined to the summit crater. Explosive, ash-producing eruptions are rare, however, on September 4, 2007 the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) captured the first satellite image of an ash plume erupting from OL, which may be indicative of a new phase of more silica-rich products and explosive activity that has not occurred since [1966][1967]. In the months prior to the eruption, thermal infrared (TIR) satellite monitoring detected an increasing number of thermal anomalies around OL. Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor analyzed with the MODLEN algorithm detected more than 30 hot spots in the last week of August and first week of September 2007, some of which were from bush fires ignited by lava flows or spatter around the volcano. Higher-resolution ASTER data confirmed the location of these burn scars associated with lava flows. ASTER also detected the appearance of an anomalous hot spot at the summit of OL in mid-June with temperatures~440°C, the presence of several new lava flows in the crater in July and August, and on September 4 measured higher temperatures (~550°C) possibly suggesting a more silicate-rich eruption. ASTER spectral emissivity data were interpreted to indicate a mixture of carbonate and silicate ash in the eruption plume from September 4. Based on the analysis of both ASTER and MODIS data combined with occasional field observations, there appear to have been 2 distinct eruptive events so far in 2007: a typical natrocarbonatite eruption confined to the summit crater in June-July, and a more intense eruption in August-September consisting of natrocarbonatite lava overflowing the crater and explosive events forming ash plumes up to~5 km high, apparently consisting of a mixture of silicate and carbonate ash. OL is one of the many volcanoes in the world, and especially Africa, that is not regularly monitored with in situ instruments. Continued satellite monitoring along with studies of past thermal activity will help determine how future eruptions and ensuing hazards may be forecasted.

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Section: Ash Plume and Burn Scarsmentioning

confidence: 99%

Section: Astermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Satellite measurements of recent volcanic activity at Oldoinyo Lengai, Tanzania

Vaughan

Kervyn

Realmuto

et al. 2008

Journal of Volcanology and Geothermal Research

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“…Before the March-April 2006 eruptions, thermal RS monitoring of OL was developed at UGhent based on daily night-time MODIS satellite data, building up from thermal RS observations at OL by Oppenheimer (1997). MODLEN, an adaptation of the MODVOLC algorithm (Wright et al 2004), is designed to detect low intensity thermal anomalies at OL, based on threshold values applied to a Normalised Thermal Index (NTI, Kervyn et al 2008).…”

Section: Thermal Rs Observationsmentioning

confidence: 99%

Voluminous lava flows at Oldoinyo Lengai in 2006: chronology of events and insights into the shallow magmatic system

et al. 2008

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The largest natrocarbonatite lava flow eruption ever documented at Oldoinyo Lengai, NW Tanzania, occurred from March 25 to April 5, 2006, in two main phases. It was associated with hornito collapse, rapid extrusion of lava covering a third of the crater and emplacement of a 3-km long compound rubbly pahoehoe to blocky aa-like flow on the W flank. The eruption was followed by rapid enlargement of a pit crater. The erupted natrocarbonatite lava has high silica content (3% SiO 2 ). The eruption chronology is reconstructed from eyewitness and news media reports and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, which provide the most reliable evidence to constrain the eruption's onset and variations in activity. The eruption products were mapped in the field and the total erupted lava volume estimated at 9.2±3.0×10 5 m 3 . The event chronology and field evidence are consistent with vent construct instability causing magma mixing and rapid extrusion from shallow reservoirs. It provides new insights into and highlights the evolution of the shallow magmatic system at this unique natrocarbonatite volcano.

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“…Thermal emissions of natrocarbonatite lava at OL were first detected using thermal remote sensing by Oppenheimer (1997). Using bands 5 (1.55-1.75 mm) and 7 Figure 3.…”

Section: Thermal Emissions Of Lengaimentioning

confidence: 99%

Thermal remote sensing of the low‐intensity carbonatite volcanism of Oldoinyo Lengai, Tanzania

Kervyn

Ernst²,

Harris

et al. 2008

International Journal of Remote Sensing

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Although Tanzania, Kenya and Ethiopia contain a number of active and potentially hazardous volcanoes, none of them are routinely or continuously monitored. Of these, Tanzania's Oldoinyo Lengai (OL) has been active almost continuously over the past two decades (since 1983). Recent activity has been confined to small-scale effusive and explosive eruptions of natrocarbonatite within the summit crater, with lava flows occasionally overflowing the crater rim and extending onto the volcano flanks. The automated MODVOLC algorithm falls short of detecting all thermal anomalies within OL's crater. The sensitivity of the algorithm is insufficient to detect anomalies of the size and magnitude presented by those at OL. We explore how Moderate Resolution Imaging Spectroradiometer (MODIS) infrared (IR) bands can still be used to monitor activity. We cross-verify our observations against field reports and higher resolution satellite images (ASTER, Landsat ETM + ). Despite the limited extent and low temperature (,585uC) of natrocarbonatite lavas, relative variations in eruption intensity and periods of increased activity alternating with periods of reduced or no detectable activity can be observed using the MODLEN algorithm. Although activity in the past two decades has been moderate at OL, a more intense explosive eruption is overdue and there is a need for routine monitoring in the future. Our work makes a case for low-cost thermal IR monitoring as an essential component of such a monitoring programme at several Tanzanian, Kenyan and Ethiopian volcanoes. The approach presented here is already available for routine use.

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Satellite observation of active carbonatite volcanism at Ol Doinyo Lengai, Tanzania

Cited by 16 publications

References 12 publications

Satellite measurements of recent volcanic activity at Oldoinyo Lengai, Tanzania

Satellite measurements of recent volcanic activity at Oldoinyo Lengai, Tanzania

Voluminous lava flows at Oldoinyo Lengai in 2006: chronology of events and insights into the shallow magmatic system

Thermal remote sensing of the low‐intensity carbonatite volcanism of Oldoinyo Lengai, Tanzania

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