The distal segment of Etna’s 2001 basaltic lava flow

Abstract

Etna's 2001 basaltic lava flow provided a good example of the distal flow segment between the flow front and stable channel, across which the flow evolves from channel-contained to dispersed. This zone was mapped with meter precision using LIDAR data collected during 2004 and 2005. These data, supported by field mapping, show that the flow front comprised eight lobes each 10 to 20 m high. The flow front appears to have advanced not as a single unit, but as a series of lobes moving forward one lobe at a time. Primary lobes were centered on the channel axis and marginal lobes were off-axis. The lobes advanced as breakouts of low-yield-strength lava from the flow core of the stalled flow front. Marginal lobes were abandoned and contributed to marginal levees flanking the transitional channel. For Etna's 2001 flow, the transitional channel is 140 m wide, 700 m long and fed a 240-m-long zone of dispersed flow; the change from stable to transitional channel occurred at a major reduction in slope. Above this, the stable channel is 5.2 km long, 55 to 105 m wide and bounded by 15-to 25-m-high levees, and the stable channel is located over a previous channel. In a final stage of activity, lava ponding at the break-in-slope that marks the terminus of the stable channel put pressure on the eastern levee, causing it to fail. Liberated lava then fed a final break-out to the east. Similar flow front-features occur at other volcanoes, indicating that similar processes are characteristic of dispersed flow zones.

Exceptional mobility of an advancing rhyolitic obsidian flow at Cordón Caulle volcano in Chile

“…Rhyolitic breakouts share many features with breakouts and squeeze-ups documented in stalling and compound basaltic flow fields 10,22 . With both compositions, lava breaks out from stalled lava flow fronts and channel margins where shear stresses are highest.…”

“…Long-term processes in compound basaltic lava flow fields are therefore both vertical (flow inflation and tumulus formation) and horizontal (creation of breakouts). Some cross-compositional commonality in lava effusion and emplacement mechanisms has been identified, including localized lava extrusion at dacitic lava flow margins 21 that has a direct basaltic equivalent 10,22 . However, similarities between rhyolitic and basaltic emplacement are largely (Fig.…”

Satellite and Ground Remote Sensing Techniques to Trace the Hidden Growth of a Lava Flow Field: The 2014–2015 Effusive Eruption at Fogo Volcano (Cape Verde)

“…Preferred pathways develop in the older portions of the liquid-cored flow as the flow advances, and these pathways can evolve into lava tube systems within a few weeks [15]. Inflation combined with flow overlapping causes a slow and mostly undetected expansion of a complex lava flow field, and can result in sudden reactivation of previously stagnating lava flow fronts [3,6,15,[22][23][24].…”

“…Quantitative measurements of the amount of magma intruded within a lava flow field and causing inflation are scant and normally carried out only on a portion of a compound lava flow field [21,[23][24][25][26][27][28]. On pahoehoe flows from Kilauea, a volumetric growth of ten times the initial flow lobe by inflation has been documented [15].…”

Morphological complexities and hazards during the emplacement of channel-fed `a`ā lava flow fields: A study of the 2001 lower flow field on Etna

“…This flow field is the subject of our study and is hereafter referred to as the 'lower flow field'. The lower flow field reached its maximum length of 6.4 km in 8 days, after which time new flow units were emplaced as overflows from the original channel, or surface flows overlying earlier units within the channel (Behncke and Neri 2003;Favalli et al 2010). Two new major flow branches later developed as a result of channel breaching.…”