Publications

Abstract

Mud volcanism is a natural phenomenon manifesting at the surface of the body with spectacular eruptions and a large variety of morphologies resulting both from explosive and effusive activity. In this study, we targeted two large (MVs) in Azerbaijan (Lokbatan and Goturdagh) characterized by different behaviors in eruptive activity. We investigated them using a multidisciplinary approach including field observation combined with drone photogrammetry, InSAR imaging, subsurface multisource survey, geotechnical analyses of mud breccia flows and numerical stability modeling in order to reveal the way the mud flows.

Lokbatan most recently erupted in August 2022. Field observations in September 2022, before significant modification by rain, reveal that this most recent eruption, albeit small in terms of extruded mud breccia, triggered the disruption of huge segmented portions of the older mud flows that extend for more than 1 km. This was identified by the formation of series of fractures recording the detachment and subsequent downhill movement of the old flow. No evident ground deformations have been observed before the eruption and, repetitive field campaigns in subsequent months do not reveal any network of fresh fractures and dislocations. On the other hand, Goturdagh MV features a constant slow extrusion of compacted mud breccia from the subsurface forming an extended >1.2 km long mud flow that continuously moves. This movement is clearly visible at the top of the MV where repetitive field observations reveal an extrusion of wet and dark colored mud breccia. Along the slope, the movement creates well-developed shear zones and compressional structures typical of slope deformations. At the bottom however, the movement seem to be discontinuous and might be triggered occasionally when the force of the new material becomes critical.

The field observations show that kilometer scale mass transport can extend at MVs for more than 1 km along the flank of these structures. The additional approaches will help us identify possible eruptive precursors and understand if external elements (tectonics, rainfall, …) can influence this mass movement. The same phenomenon is likely happening at many other large-scale features worldwide.

How to cite: Mazzini, A., Jodry, C., Broz, P., Akhmanov, G., Blahůt, J., Lupi, M., Karimova, N., Braize, D., Nobile, A., Khasayeva-Huseynova, A., and Guliyev, I.: Mud volcanism and creeping mud flows, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9633, https://doi.org/10.5194/egusphere-egu23-9633, 2023.

Abstract

Azerbaijan hosts the highest density of subaerial mud volcanoes on Earth. The morphologies characterizing these structures vary depending on their geological setting, frequency of eruption, and transport processes during the eruptions. Lokbatan is possibly the most active mud volcano on Earth exhibiting impressive bursting events every ∼5 years. These manifest with impressive gas flares that may reach more than 100 meters in height and the bursting of thousands of m3 of mud breccia resulting in spectacular mud flows that extend for more than 1.5 kilometres. Unlike other active mud volcanoes, to our knowledge Lokbatan never featured any visual evidence of enduring diffuse degassing (e.g., active pools and gryphons) at and near the central crater. Only a very small new-born gryphon was intermittently active in 2019 (with negligible flow). Gas flux measurements completed with a closed-chamber technique reveal extremely low values throughout the structure with average CH4=1.36  tonnes yr−1 and CO2=11.85 tonnes yr−1. We suggest that after eruptive events, the mud breccia is able to seal the structure preventing gas release and thereby promoting overpressure build-up in the subsurface. This self-sealing mechanism allows a fast recharge of Lokbatan resulting in more frequent and powerful explosive episodes. Our field observations reveal the presence of large (up to ∼50,000 m3) stratified blocks that were originally part of a large crater cone. These blocks were rafted >1 km from the vent on top of mud breccia flows. We use a model based on lubrication theory to show that it is reasonable to transport blocks this large and this far provided the underlying mud flow was thick enough and the blocks are large enough. The presence of large rafted blocks is not a unique phenomenon observed at Lokbatan mud volcano and is documented at other large-scale structures both onshore and offshore.

Azerbaijan hosts the largest concentration of mud volcanoes (MVs) on Earth. Here, high sedimentation rates and deposition of thick organic-rich series resulted in petroleum basin formation and, in turn, created the ideal setting and conditions to generate widespread sedimentary volcanism. Some of the regions hosting these piercements have been broadly studied, while others (e.g. the Shamakhy-Gobustan region) are less explored. In this seismically more active part of the country, the tectonic control plays a stronger role for the emplacement of diapirs and fluid migration.