29 research outputs found
The Hidden Giant: How a rift pulse triggered a cascade of sector collapses and voluminous secondary massâtransport events in the early evolution of Santorini
Volcanic island sector collapses have the potential to trigger devastating tsunamis and volcanic eruptions that threaten coastal communities and infrastructure. Considered one of the most hazardous volcano-tectonic regions in the world, the Christiana-Santorini-Kolumbo Volcanic Field (CSKVF) lies in the South Aegean Sea in an active rift zone. Previous studies identified an enigmatic voluminous mass-transport deposit west and east of Santorini emplaced during the early evolution of the edifice. However, the distribution and volume as well as the nature and emplacement dynamics of this deposit remained unknown up to now. In this study, we use an extensive dataset of high-resolution seismic profiles to unravel the distribution and internal architecture of this deposit. We show that it is located in all basins surrounding Santorini and has a bulk volume of up to 125 km3, thus representing the largest known volcanic island mass-transport deposit in the entire Mediterranean Sea. We propose that the deposit is the result of a complex geohazard cascade that was initiated by an intensive rift pulse. This rifting event triggered a series of smaller precursory mass-transport events before large-scale sector collapses occurred on the northeastern flank of the extinct Christiana Volcano and on the southeastern flank of the nascent Santorini. This was followed by the emplacement of large-scale secondary sediment failures on the slopes of Santorini, which transitioned into debris and turbidity flows that traveled far into the neighboring rift basins. Following this cascade, a distinct change in the volcanic behavior of the CSKVF occurred, suggesting a close relationship between crustal extension, mass transport, and volcanism. Cascading geohazards seem to be more common in the evolution of marine volcanic systems than previously appreciated. Wider awareness and a better understanding of cascading effects are crucial for more holistic hazard assessments
Hazardous explosive eruptions of a recharging multi-cyclic island arc caldera
Caldera-forming eruptions of silicic volcanic systems are among the most
devastating events on Earth. By contrast, post-collapse volcanic activity
initiating new caldera cycles is generally considered less hazardous.
Formed after Santoriniâs latest caldera-forming eruption of ~1600âbce, the
Kameni Volcano in the southern Aegean Sea enables the eruptive evolution
of a recharging multi-cyclic caldera to be reconstructed. Santoriniâs
eruptive record has been documented by onshore products and historical
descriptions of mainly effusive eruptions dating back to 197âbce. Here we
combine high-resolution seismic reflection data with cored lithologies
from International Ocean Discovery Program Expedition 398 at four sites to
determine the submarine architecture and volcanic history of intra-caldera
deposits from Kameni. Our shore-crossing analysis reveals the deposits
of a submarine explosive eruption that produced up to 3.1âkm3
of pumice
and ash, which we relate to a historical eruption in 726âce. The estimated
volcanic explosivity index of magnitude 5 exceeds previously considered
worst-case eruptive scenarios for Santorini. Our finding that the Santorini
caldera is capable of producing large explosive eruptions at an early stage
in the caldera cycle implies an elevated hazard potential for the eastern
Mediterranean region, and potentially for other recharging silicic calderas
When There Is No Offset: A Demonstration of Seismic Diffraction Imaging and Depth-Velocity Model Building in the Southern Aegean Sea
A vast majority of marine geological research is based on academic seismic data collected with single-channel systems or short-offset multichannel seismic cables, which often lack reflection moveout for conventional velocity analysis. Consequently, our understanding of Earth processes often relies on seismic time sections, which hampers quantitative analysis in terms of depth, formation thicknesses, or dip angles of faults. In order to overcome these limitations, we present a robust diffraction extraction scheme that models and adaptively subtracts the reflected wavefield from the data. We use diffractions to estimate insightful wavefront attributes and perform wavefront tomography to obtain laterally resolved seismic velocity information in depth. Using diffraction focusing as a quality control tool, we perform an interpretation-driven refinement to derive a geologically plausible depth-velocity model. In a final step, we perform depth migration to arrive at a spatial reconstruction of the shallow crust. Further, we focus the diffracted wavefield to demonstrate how these diffraction images can be used as physics-guided attribute maps to support the identification of faults and unconformities. We demonstrate the potential of this processing scheme by its application to a seismic line from the Santorini Amorgos Tectonic Zone, located on the Hellenic Volcanic Arc, which is notorious for its catastrophic volcanic eruptions, earthquakes, and tsunamis. The resulting depth image allows a refined fault pattern delineation and, for the first time, a quantitative analysis of the basin stratigraphy. We conclude that diffraction-based data analysis has a high potential, especially when the acquisition geometry of seismic data does not allow conventional velocity analysis
VolcanoâTectonic Evolution of the ChristianaâSantoriniâKolumbo Rift Zone
Located on the Hellenic Arc, the Christiana-Santorini-Kolumbo (CSK) rift zone represents one of the most active and hazardous volcano-tectonic systems in the Mediterranean. Although this rift zone has been intensively studied, its tectonic evolution and the interplay of volcanism and tectonism are still poorly understood. In this study, we use high-resolution reflection seismic imagery to reconstruct the opening of the rift basins. For the first time, we relate the activity of individual faults with the activity of specific volcanic centers in space and time. Our analysis shows a pre-volcanic NNE-SSW-oriented paleo basin underneath the CSK volcanoes, representing a transfer zone between Pliocene ESE-WNW-oriented basins, which was overprinted by a NE-SW-oriented tectonic regime hosting Late Pliocene volcanism that initiated at the Christiana Volcano. All subsequent volcanoes evolved parallel to this trend. Two major Pleistocene tectonic pulses preceded fundamental changes in the volcanism of the CSK rift including the occurrence of widespread small-scale volcanic centers followed by focusing of activity at Santorini with increasing explosivity. The observed correlation between changes in the tectonic system and the magmatism of the CSK volcanoes suggests a deep-seated tectonic control of the volcanic plumbing system. In turn, our analysis reveals the absence of large-scale faults in basin segments affected by volcanism indicating a secondary feedback mechanism on the tectonic system. A comparison with the evolution of the neighboring Kos-Nisyros-Yali volcanic field zone and Rhodos highlights concurrent regional volcano-tectonic changes, suggesting a potential arc-wide scale of the observed volcano-tectonic interplay.
Key Points
We reconstruct the volcano-tectonic evolution of the Christiana-Santorini-Kolumbo rift zone using multichannel seismic data
The overprint of a Pleistocene NE-SW striking fault system on a Pliocene E-W oriented system initiated the emergence of volcanism
Regional tectonics had a primary control on the volcanic plumbing system, while magmatism had a secondary influence on the tectonic syste
Spatio-temporal evolution of the Kolumbo Volcanic Chain and its link to the volcanic plumbing system of Santorini
Key Points
High-resolution reflection seismic data reveals that the internal architecture of the
Kolumbo Volcanic Chain
The Kolumbo Volcanic Chain evolved during two episodes along NE-SW striking normal
faults
A prominent volcanic ridge connects the Kolumbo Volcanic Chain with Santorini
highlighting a former connection between both systems
Abstract
The Christiana-Santorini-Kolumbo volcanic field in the southern Aegean Sea is one of the most
hazardous volcanic regions in the world. Forming the northeastern part of this volcanic field, the
Kolumbo Volcanic Chain (KVC) comprises more than
submarine volcanic cones. However,
due to their inaccessibility, little is known about the spatio-temporal evolution and tectonic control
of these submarine volcanoes and their link to the volcanic plumbing system of Santorini. In this
study, we use multichannel reflection seismic imaging to study the internal architecture of the
KVC and its link to Santorini. We show that the KVC evolved during two episodes, which initiated
at ~1 Ma with the formation of mainly effusive volcanic edifices along a NE-SW trending zone.
The cones of the second episode were formed mainly by submarine explosive eruptions between
0.7 and 0.3 Ma and partly developed on top of volcanic edifices from the first episode. We identify
two prominent normal faults that underlie and continue the two main trends of the KVC, indicating
a direct link between tectonics and volcanism. In addition, we reveal several buried volcanic
centers and a distinct volcanic ridge connecting the KVC with Santorini, suggesting a connection
between the two volcanic centers in the past. This connection was interrupted by a major tectonic
event and, as a result, the two volcanic systems now have separate, largely independent plumbing
systems despite their proximit
VolcanoâTectonic Evolution of the ChristianaâSantoriniâKolumbo Rift Zone
Located on the Hellenic Arc, the ChristianaâSantoriniâKolumbo (CSK) rift zone represents one of the most active and hazardous volcanoâtectonic systems in the Mediterranean. Although this rift zone has been intensively studied, its tectonic evolution and the interplay of volcanism and tectonism are still poorly understood. In this study, we use highâresolution reflection seismic imagery to reconstruct the opening of the rift basins. For the first time, we relate the activity of individual faults with the activity of specific volcanic centers in space and time. Our analysis shows a preâvolcanic NNEâSSWâoriented paleo basin underneath the CSK volcanoes, representing a transfer zone between Pliocene ESEâWNWâoriented basins, which was overprinted by a NEâSWâoriented tectonic regime hosting Late Pliocene volcanism that initiated at the Christiana Volcano. All subsequent volcanoes evolved parallel to this trend. Two major Pleistocene tectonic pulses preceded fundamental changes in the volcanism of the CSK rift including the occurrence of widespread smallâscale volcanic centers followed by focusing of activity at Santorini with increasing explosivity. The observed correlation between changes in the tectonic system and the magmatism of the CSK volcanoes suggests a deepâseated tectonic control of the volcanic plumbing system. In turn, our analysis reveals the absence of largeâscale faults in basin segments affected by volcanism indicating a secondary feedback mechanism on the tectonic system. A comparison with the evolution of the neighboring KosâNisyrosâYali volcanic field zone and Rhodos highlights concurrent regional volcanoâtectonic changes, suggesting a potential arcâwide scale of the observed volcanoâtectonic interplay.Plain Language Summary:
How do regional tectonic movements and large volcanoes interact? Seismological studies indicate complex volcanoâtectonic feedback links, but, so far, information on the longâterm interactions between tectonics and volcanism is rarely available. The ChristianaâSantoriniâKolumbo (CSK) rift zone lies in the Aegean Sea and is notorious for its devastating volcanic eruptions, earthquakes, and tsunamis. This region offers the opportunity to study volcanoâtectonic interactions over several million years. In this study, we use highâresolution seismic imagery to reconstruct the evolution of the rift basins and the CSK volcanoes. We find that all volcanoes lie in a Pliocene transfer zone connecting extensional basins. Volcanism initiated as this older tectonic regime was intersected by a NEâSWâdirected fault system. Subsequently, all volcanoes evolved parallel to this trend. Several distinct tectonic reorganizations occurred in the Pleistocene, which had a pronounced influence on the CSK volcanoes. In turn, our analysis indicates that the emergence of volcanism also impacted the tectonic evolution of the rift system hindering the evolution of largeâscale normal faults in the volcanic basins. The observed tectonic reorganizations seem to reflect major changes in the stress regime of the Hellenic Arc, potentially also affecting adjacent volcanic centers whose volcanoâtectonic evolution is only poorly constrained so far.Key Points:
We reconstruct the volcanoâtectonic evolution of the ChristianaâSantoriniâKolumbo rift zone using multichannel seismic data.
The overprint of a Pleistocene NEâSW striking fault system on a Pliocene EâW oriented system initiated the emergence of volcanism.
Regional tectonics had a primary control on the volcanic plumbing system, while magmatism had a secondary influence on the tectonic system.German Research Foundation DFGhttps://doi.org/10.26022/IEDA/33102