Flank instability of coastal and ocean island volcanoes: Why it is not enough to look at the tip of the iceberg

Author(s):  
Morelia Urlaub

<p>Volcanoes are among the most rapidly growing geological structures on Earth. Consequently, their edifices suffer structural instability that may result in lateral flank collapses, such as the 1980 Mt St Helens event or the 2018 collapse of Anak Krakatau (Indonesia). The seafloor displays the geological remnants of collapses of nearly all ocean island volcanoes, including Hawaii and the Canary Islands. Such collapses and their associated tsunamis are among the largest and most disastrous natural processes on Earth, because of the enormous energy involved. Numerous coastal and ocean island volcanoes worldwide show signs of flank instability, documented by ground deformation measurements. However, it is difficult to evaluate their hazard potential mainly due to a lack of understanding of the causes of collapse. For coastal and ocean island volcanoes, most research and the vast majority of monitoring activities are biased towards the often comparatively small part of the volcano above sea level, while the largest part of the volcanic edifice is typically submerged in water. Using the example of Mount Etna (Italy) as well as several other case studies, I demonstrate that shoreline crossing analyses of volcano-tectonic structures and edifice deformation are necessary for understanding the mechanisms that control the volcano’s structural stability. I further argue that the earliest and most important precursory signals for imminent edifice collapse may occur below sea level. Data acquisition and monitoring in the deep sea is technologically and logistically challenging, but possible. It significantly extends onshore data sets with the potential to revolutionise our current understanding and hazard monitoring.</p>

2021 ◽  
Author(s):  
Morelia Urlaub

<p>Volcanoes are among the most rapidly growing geological structures on Earth. Consequently, their edifices suffer structural instability that may result in lateral flank collapses, such as the 1980 Mt St Helens event or the 2018 collapse of Anak Krakatau (Indonesia). The seafloor displays the geological remnants of collapses of nearly all ocean island volcanoes, including Hawaii and the Canary Islands. Such collapses and their associated tsunamis are among the largest and most disastrous natural processes on Earth, because of the enormous energy involved. Numerous coastal and ocean island volcanoes worldwide show signs of flank instability, documented by ground deformation measurements. However, it is difficult to evaluate their hazard potential mainly due to a lack of understanding of the causes of collapse. For coastal and ocean island volcanoes, most research and the vast majority of monitoring activities are biased towards the often comparatively small part of the volcano above sea level, while the largest part of the volcanic edifice is typically submerged in water. Using the example of Mount Etna (Italy) as well as several other case studies, I demonstrate that shoreline crossing analyses of volcano-tectonic structures and edifice deformation are necessary for understanding the mechanisms that control the volcano’s structural stability. I further argue that the earliest and most important precursory signals for imminent edifice collapse may occur below sea level. Data acquisition and monitoring in the deep sea is technologically and logistically challenging, but possible. It significantly extends onshore data sets with the potential to revolutionise our current understanding and hazard monitoring. </p>


1999 ◽  
Vol 11 ◽  
pp. 161-172 ◽  
Author(s):  
W Bijl ◽  
R Flather ◽  
JG de Ronde ◽  
T Schmith
Keyword(s):  

2010 ◽  
Vol 47 (8) ◽  
pp. 1079-1091 ◽  
Author(s):  
John Shaw ◽  
Carl L. Amos ◽  
David A. Greenberg ◽  
Charles T. O’Reilly ◽  
D. Russell Parrott ◽  
...  

Tidal models for the Bay of Fundy, Canada — site of the highest recorded modern tide — show that tidal amplification began in the early Holocene and by ca. 5000 BP the range was almost 80% of the present range. Empirical data consisting of 146 sea-level index points and other observations appear to contradict model results. Aggregated relative sea-level data for Chignecto Bay and Minas Basin show that rapid tidal expansion began ca. 3400 BP. However, if we separate these two geographically separate data sets, evidence for this rapid late-Holocene tidal expansion is confined to Minas Basin. We explain this singularity by positing a barrier at the mouth of Minas Basin, at the Minas Passage, that delayed tidal expansion. With the rapid breakdown of this barrier and near-instantaneous tidal expansion, water temperature dropped, tidal currents and turbidity increased, and the form of the inner estuary was changed from lagoonal–mesotidal to macrotidal. We argue that the catastrophic breakdown of the barrier is related in the aboriginal legend of Glooscap, showing that aboriginal peoples observed the rapid environmental changes and preserved an oral record for 3400 years.


2014 ◽  
Vol 71 (4) ◽  
Author(s):  
Ami Hassan Md Din ◽  
Sahrum Ses ◽  
Kamaludin Mohd Omar ◽  
Marc Naeije ◽  
Omar Yaakob ◽  
...  

The utilization of satellite altimeter data sets from previous and present satellite altimeter missions is imperative to both oceanographic and geodetic applications. The important parameter that can be derived from satellite altimeter is sea level anomaly, while it is also fundamental for sea level monitoring, geoid determination and current circulations study. This paper presents an effort to determine sea level anomaly for Malaysian seas from six satellite altimeter missions; TOPEX, JASON1, JASON2, ERS1, ERS2 and ENVISAT. The best range and geophysical corrections for Malaysian seas were also investigated in this study by evaluating two state of the art corrections available for 9 years of TOPEX satellite altimeter (from January 1993 to December 2001). Sea level data retrieval and reduction were carried out using the Radar Altimeter Database System (RADS). The comparison of near-simultaneous altimeter and tide gauges observations showed good agreement with the correlations are higher than 0.87 at Tioman Island, Langkawi Island and Kota Kinabalu. This paper introduces RADS and deals with determination of sea level anomaly using the best range and geophysical corrections in Malaysian seas.


2006 ◽  
Vol 24 (6) ◽  
pp. 1483-1491 ◽  
Author(s):  
I. Vilibic

Abstract. The paper comprises the calculations of amplitudes and phases of tidal harmonic constituents, performed on hourly sea level data recorded at the Split tide gauge in the period 1957-2001. Interannual changes in all constituents have been detected, stronger in phases than in amplitudes. For example, the estimated change in M2 amplitude and phase is 22% (1.31 cm) and 24.9° between the 1962–1978 and 1957–1961 periods, respectively. Some of the differences are generated artificially throughout the measurements (clock errors, positioning and stretching of a chart) and within the digitising procedure, rather than by natural processes and changes (e.g. changes in mean sea level). This is the reason why the M2 and K1 amplitudes were recomputed with 3–4 mm larger values using newer software, thereby decreasing their standard deviation by 60–70% in the 1986–1995 period. Artificial errors may be reduced by the upgrading of digitising software; however, most of the errors still remain in the series. These errors may have repercussions when trying to explain some unusual findings: the energy of de-tided sea level series at the M2 tidal period (12.4 h) has been assumed previously to be a result of nonlinear coupling, but it may be caused, at least partly, by timing errors in the time series.


2005 ◽  
Vol 23 (1) ◽  
pp. 9 ◽  
Author(s):  
A Singh ◽  
T Aung

Barometric pressure and sea level data sets from the South Pacific Sea Level and Climate Monitoring Project funded by AusAID were analysed for twelve Tropical Pacific island countries. During mid-1997 and 1998 pressure anomalies over the Pacific region were strongly positive and sea level dropped significantly. As a consequence, sea level trends in the Pacific region suddenly changed from positive to negative. It was believed that the delayed effect of the 1997 strong El Ni�o episode was directly linked to these positive pressure anomalies. The same observations were made in 2002 and 2003 during another El Ni�o episode which was however not as strong as the previous one. The La Ni�a episode which followed the 1997-98 El Ni�o in 1999 had opposite effects. The pressure anomalies were negative and the sea level anomalies were positive. While the thermal effect due to global warming is still the cause of sea level rise in the Pacific region, it is clearly evident that the barometric pressure effect on sea level is more abrupt and it can overshadow the other effects at least temporarily.


2018 ◽  
Author(s):  
Benjamin P. Horton ◽  
◽  
Ian Shennan ◽  
Sarah L. Bradley ◽  
Niamh Cahill ◽  
...  

2019 ◽  
Vol 93 (12) ◽  
pp. 2651-2660 ◽  
Author(s):  
Sergey Samsonov

AbstractThe previously presented Multidimensional Small Baseline Subset (MSBAS-2D) technique computes two-dimensional (2D), east and vertical, ground deformation time series from two or more ascending and descending Differential Interferometric Synthetic Aperture Radar (DInSAR) data sets by assuming that the contribution of the north deformation component is negligible. DInSAR data sets can be acquired with different temporal and spatial resolutions, viewing geometries and wavelengths. The MSBAS-2D technique has previously been used for mapping deformation due to mining, urban development, carbon sequestration, permafrost aggradation and pingo growth, and volcanic activities. In the case of glacier ice flow, the north deformation component is often too large to be negligible. Historically, the surface-parallel flow (SPF) constraint was used to compute the static three-dimensional (3D) velocity field at various glaciers. A novel MSBAS-3D technique has been developed for computing 3D deformation time series where the SPF constraint is utilized. This technique is used for mapping 3D deformation at the Barnes Ice Cap, Baffin Island, Nunavut, Canada, during January–March 2015, and the MSBAS-2D and MSBAS-3D solutions are compared. The MSBAS-3D technique can be used for studying glacier ice flow at other glaciers and other surface deformation processes with large north deformation component, such as landslides. The software implementation of MSBAS-3D technique can be downloaded from http://insar.ca/.


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