Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

Browse

Filters

2022 - 20242

Settings

Has files: YesSubject: search.filters.subject.Morphometry

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    The complexities of assessing volcanic hazards along the Cameroon Volcanic Line using spatial distribution of monogenetic volcanoes
    (Elsevier B V, Amsterdam, 2022-07) Schmidt C; Laag C; Whitehead M; Profe J; Tongwa Aka F; Hasegawa T; Kereszturi G
    Volcanic eruptions represent hazards for local communities and infrastructure. Monogenetic volcanoes (usually) erupt only once, and then volcanic activity moves to another location, making quantitative assessment of eruptive hazards challenging. Spatio-temporal patterns in the occurrence of these eruptions may provide valuable information on locations more likely to host future eruptions within monogenetic volcanic fields. While the eruption histories of many stratovolcanoes along the Cameroon Volcanic Line (CVL) are relatively well studied, only fragmentary data exist on the distribution and timing of this region's extensive monogenetic volcanism (scoria cones, tuff rings, maars). Here, we present for the first time a catalog of monogenetic vents on the CVL. These were identified by their characteristic morphologies using field knowledge, the global SRTM Digital Elevation Model (30 m resolution), and satellite imagery. More than ~1100 scoria cones and 50 maars/tuff rings were identified and divided into eight monogenetic volcanic fields based on the visual assessment of clustering and geological information. Spatial analyses show a large range of areal densities between the volcanic fields from >0.2 km−2 to 0.02 km−2 from the southwest towards the northeast. This finding is in general agreement with previous observations, indicating closely spaced and smaller edifices typical of fissure-fed eruptions on the flanks of Bioko and Mt. Cameroon in the southwest, and a more focused plumbing system resulting in larger edifices of lower spatial density towards the northeast. Spatial patterns were smoothed via kernel density estimates (KDE) using the Summed Asymptotic Mean Squared Error (SAMSE) bandwidth estimator, the results of which may provide an uncertainty range for a first-order hazard assessment of vent opening probability along the CVL. Due to the scarce chronological data and the complex structural controls across the region, it was not possible to estimate the number of vents formed during the same eruptive events. Similarly, the percentage of hidden (buried, eroded) vents could not be assessed with any acceptable statistical certainty. Furthermore, the impact of different approaches (convex hull, minimum area rectangle and ellipse, KDE isopaches) to define volcanic field boundaries on the spatial distribution of vents was tested. While the KDE boundary definition appears to reflect the structure of a monogenetic volcanic field better than other approaches, no ideal boundary definition was found. Finally, the dimension of scoria cones (approximated by their basal diameters) across the CVL was contrasted to the specific geodynamic setting. This region presents a complex problem for volcanic hazard analysis that cannot be solved through basic statistical methods and, thus, provides a potential testbed for novel, multi-disciplinary approaches.
  • Thumbnail Image
    Item
    Morphometric analysis of monogenetic volcanoes in the Garrotxa Volcanic Field, Iberian Peninsula
    (Elsevier B V, Amsterdam, 2024-11-15) Pedrazzi D; Kereszturi G; Geyer A; Bolós X; Granell J; Planagumà L; Martí J; Cerda D
    The Garrotxa Volcanic Field is situated in the northeast region of the Iberian Peninsula. It represents the most recent volcanic area within the Catalan Volcanic Zone, which is one of the volcanic provinces of the European Rift System, featuring over 50 dispersed eruptive vents. This study presents a comprehensive morphometric analysis of volcanic edifices, aiming to enhance our understanding of both volcanostratigraphy and the geomorphology of landforms within the Garrotxa Volcanic Field. Our methodology involved extensive fieldwork and detailed analysis of Digital Elevation Models (DEMs) to precisely determine the spatial distribution and morphometric parameters of the best-preserved volcanic structures in the area. The Garrotxa Volcanic Field exhibits an uneven spatial distribution of various volcanic landforms, with approximately 50 % comprising magmatic cones, primarily formed through Strombolian eruptions. The remaining 50 % is evenly divided between magmatic-phreatomagmatic volcanoes and phreatomagmatic tuff rings-maars. The morphometric characteristics of the three genetic types overlap significantly, showing no clear differences, although a few distinctions can sometimes be identified. The Garrotxa Volcanic Field displays a variety of eruption styles: 46 % of the identified eruptive sequences begin with phreatomagmatic activity, while 54 % start with predominantly magmatic explosive activity. Most eruptions show a transition through different phases. Data also indicate that the morphometric variability at the Garrotxa Volcanic Field stems from differences in the properties of pyroclastic sequences, resulting from their diverse eruption styles, as well as pre- and post-eruptive factors. Consequently, the results of the morphometric analysis are deemed insufficient for establishing a reliable chronology for the Garrotxa Volcanic Field