Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

Abstract

The Rocche Rosse lava flow marks the most recent rhyolitic extrusion on Lipari island (Italy), and preserves evidence for a multi-stage emplacement history. Due to the viscous nature of the advancing lava (10 8 to 10 10 Pa s), indicators of complex emplacement processes are preserved in the final flow. This study focuses on structural mapping of the flow to highlight the interplay of cooling, crust formation and underlying slope in the development of rhyolitic lavas. The flow is made up of two prominent lobes, small (< 0.2 m) to large (> 0.2 m) scale folding and a channelled geometry. Foliations dip at 2-4°over the flatter topography close to the vent, and up to 30-50°over steeper mid-flow topography. Brittle faults, tension gashes and conjugate fractures are also evident across flow. Heterogeneous deformation is evident through increasing fold asymmetry from the vent due to downflow cooling and stagnation. A steeper underlying topography mid-flow led to development of a channelled morphology, and compression at topographic breaks resulted in fold superimposition in the channel. We propose an emplacement history that involved the evolution through five stages, each associated with the following flow regimes: (1) initial extrusion, crustal development and small scale folding; (2) extensional strain, stretching lineations and channel development over steeper topography; (3) compression at topographic break, autobrecciation, lobe development and medium scale folding; (4) progressive deformation with stagnation, large-scale folding and refolding; and (5) brittle deformation following flow termination. The complex array of structural elements observed within the Rocche Rosse lava flow facilitates comparisons to be made with actively deforming rhyolitic lava flows at the Chilean volcanoes of Chaitén and Cordón Caulle, offering a fluid dynamic and structural framework within which to evaluate our data.

Chrono-stratigraphy of the youngest (last 1500 years) rhyolitic eruptions of Lipari (Aeolian Islands, Southern Italy) and implications for distal tephra correlations

“…1b). It is a lobate, tongue-like (up to 60 m thick), obsidian-rich lava flow with developed ramps and flow foliation, and blocky and cracked surface (Shields et al, 2016;Bullock et al, 2018). The lava flow originates from the lowered north-eastern rim of a 30-m-high, low-profile tephra ring (400 m large in diameter), hosted within the older Monte Pilato crater, and it reaches the sea in the area between Porticello and Acquacalda.…”

The Eruption of Submarine Rhyolite Lavas and Domes in the Deep Ocean – Havre 2012, Kermadec Arc

“…In both settings, the breccia is autoclastic; in the Havre case, both quench fragmentation and dynamic stressing probably operated. Among the best subaerial examples of silicic, blocky lavas are the Roche Rosse rhyolite lava (Italy; ∼2 km long, 0.03 km 3 ; Bullock et al, 2018), the Cordón-Caulle obsidian lava (Chile; ∼3.6 km long, 0.8 km 3 ; Tuffen et al, 2013) and rhyolite lavas of Newberry volcano (e.g., Big Obsidian Flow, 1.8 km long, ∼0.13 km 3 ; Interlake Obsidian Flow, 1.8 km long, 0.025 km 3 ;MacLeod et al, 1995), all of which have dimensions comparable to the Havre 2012 lavas. The arcuate surface ridges on the Havre lavas, especially those on A (Figure 8), appear to be identical to similar ridges on subaerial silicic lavas (commonly referred to as surface folds, compressional ridges or ogives).…”

Vikrahraun—the 1961 basaltic lava flow eruption at Askja, Iceland: morphology, geochemistry, and planetary analogs

“…Festoons also have been referred to as pressure ridges, ogives, and surface folds (Andrews et al 2021 ). Documentation of terrestrial festoons are also unstandardized, describing a variety volcanic textures such as: small-scale pahoehoe ropes (Wentworth and MacDonald 1953 ; Larson 1991 ; Hon et al 1994 ); large-scale flood basalt ribs, ridges, or folds (Fink 1980 ); large-scale convex ridges of aʻa clasts on Rangitoto Island, Auckland (Lowe et al 2017 ) and in the 2018 Sierra Negra Eruption, Galápagos, Ecuador (Soule et al 2019 ); large-scale convex andesitic and dacitic ridges called flow “wrinkles” in the young Gassan edifice, Japan (Oizumi et al 2018 ); and large-scale convex rhyolitic flow ridges on the Obsidian Flow at Glass Mountain, California and on the Rocche Rosse Flow of Lipari, Italy (Fink 1983 ; Bullock et al 2018 ; Andrews et al 2021 ). Interestingly, rhyolitic festoons are similar in size and distribution to the festoons observed in the 1961 Askja flow, despite the difference in composition (Table 3 ).…”