Subaqueous lava flow lobes, observed on ROV KAIKO dives off Hawaii

Umino, Susumu; Lipman, Peter W.; Obata, Sumie

doi:10.1130/0091-7613(2000)028<0503:slfloo>2.3.co;2

Cited by 10 publications

(21 citation statements)

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“…Observed where subaerial lavas flow onto the flanks of Kilauea, Hawaii (Hon et al 1994), inflation serves as a model for the emplacement of even the largest flows of flood basalt, but at lower effusion rates than previously estimated ; Thordarson and Self 1998). The morphology of inflated flow lobes and sheet flows observed for subaerial flows (Walker 1991;Wilmoth and Walker 1993;Rossi and Gudmundsson 1996;Self et al 1998) provides a guide for interpreting features of modern seafloor basalts (Applegate and Embley 1992;Umino et al 2000).…”

Section: Introductionmentioning

confidence: 96%

Vesicular komatiites, 3.5-Ga Komati Formation, Barberton Greenstone Belt, South Africa: inflation of submarine lavas and origin of spinifex zones

Dann

2001

Bulletin of Volcanology

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Komatiites of the 3.5-Ga Komati Formation are ultramafic lavas (>23% MgO) erupted in a submarine, lava plain environment. Newly discovered vesicular komatiites have vesicular upper crusts disrupted by synvolcanic structures that are similar to inflation-related structures of modern lava flows. Detailed outcrop maps reveal flows with upper vesicular zones, 2-15 m thick, which were (1) rotated by differential inflation, (2) intruded by dikes from the interior of the flow, (3) extended, forming a flooded graben, and/or (4) entirely engulfed. The largest inflated structure is a tumulus with 20 m of surface relief, which was covered by a compound flow unit of spinifex flow lobes. The lava that inflated and rotated the upper vesicular crust did not vesiculate, but crystallized as a thick spinifex zone with fist-size skeletal olivine. Instead of representing rapidly cooled lava, the spinifex zone cooled slowly beneath an insulating upper crust during inflation. Overpressure of the inflating lava may have inhibited vesiculation. This work describes the oldest vesicular komatiites known, illustrates the first field evidence for inflated structures in komatiite flows, proposes a new factor in the development of spinifex zones, and concludes that the inflation model is useful for understanding the evolution of komatiite submarine flow fields.

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Section: Introductionmentioning

confidence: 96%

Vesicular komatiites, 3.5-Ga Komati Formation, Barberton Greenstone Belt, South Africa: inflation of submarine lavas and origin of spinifex zones

Dann

2001

Bulletin of Volcanology

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“…Lobate sheet flows, pillow lavas and hollow, tumulus-like lobes have been photographed on gentle slopes by remotely operated vehicles (Umino et al 2000), but steeper slopes (25-40 • ) were observed by Tribble (1991) to be dominated by loose debris with only 20% pillow lavas. Narrow, tubefed active lava streams, 0.7-1.5 m wide, were observed carrying lava directly down-slope beyond the maximum visible depth of 50 m; bathymetric data suggest that this slope continues to 250 m depth (Tribble 1991).…”

Section: Pāhoehoementioning

confidence: 99%

Lava penetrating water: the different behaviours of pāhoehoe and ‘a‘ā at the Nesjahraun, Þingvellir, Iceland

et al. 2011

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The Nesjahraun is a basaltic lava flow erupted from a subaerial fissure, extending NE along the Þingvellir graben from the Hengill central volcano. It produced pāhoehoe lava followed by 'a'ā. The Nesjahraun entered Iceland's largest lake, Þing-vallavatn, along its southern shore during both phases of the eruption and exemplifies lava flowing into water in a lacustrine environment in the absence of powerful wave action. This study combines airborne Light Detection And Ranging (LiDAR), sidescan sonar and Chirp seismic data with field observations to investigate the behaviour of the lava as it entered the water. Pāhoehoe sheet lava was formed during the early stages of the eruption. Along the shoreline, stacks of thin (5-20 cm thick), vesicular, flows rest upon and surround low (<5 m) piles of coarse, unconsolidated, variably oxidised spatter. Clefts within the lava run inland from the lake. These are 2-5 m wide, >2 m deep, ∼50 m long, spaced ∼50 m apart and have sub-horizontal striations on the walls. They likely represent channels or collapsed tubes along which lava was delivered into the water. A circular rootless cone, Eldborg, formed when water infiltrated a lava tube. Offshore from the pāhoehoe lavas, the gradient of the flow surface steepens, suggesting a change in Editorial responsibility: J.D.L. White flow regime and the development of a talus ramp. Later, the flow was focused into a channel of 'a'ā lava, ∼200-350 m wide. This split into individual flow lobes 20-50 m wide along the shore. 'A'ā clinker is exposed on the water's edge, as well as glassy sand and gravel, which has been locally intruded by small (<1 m), irregularly shaped, lava bodies. The cores of the flow lobes contain coherent, but hackly-fractured lava. Mounds consisting predominantly of scoria lapilli and the large paired half-cone of Grámelur were formed in phreatomagmatic explosions. The 'a'ā flow can be identified underwater over 1 km offshore, and the sidescan data suggest that the flow lobes remained coherent flowing down a gradient of <10 • . The Nesjahraun demonstrates that, even in the absence of ocean waves, phreatomagmatic explosions are ubiquitous and that pāhoehoe flows are much more likely to break up on entering the water than 'a'ā flows, which, with a higher flux and shallow underlying surface gradient, can penetrate water and remain coherent over distances of at least 1 km.

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“…Although rocks exhibiting a number of eruptive styles are included here, the criterion for subdivision is the occurrence of subvertical elongate fractures filled with quenched glass and hyaloclastite (e.g., Sections 206-1256D-21R-1 and 40R-1) at the top of the lava flows. These features indicate flow-lobe inflation that requires eruption onto a subhorizontal surface at less than a few degrees (Umino et al, 2000(Umino et al, , 2002, suggesting offaxial flows.…”

Section: Inflated Flowsmentioning

confidence: 99%

“…These features indicate flow-lobe inflation, which requires eruption onto a subhorizontal surface with less than a few degrees slope (Umino et al, 2000(Umino et al, , 2002; therefore, it is unlikely that such lavas formed on the ridge slope. Such inflation features are not observed in cores deeper in Hole 1256D.…”

Section: Expedition 309/312 Scientists Expedition 309/312 Summarymentioning

confidence: 99%