Volcanic Geomorphology 

Volcanism generates diverse geoforms that link endogenous and exogenous processes in an obvious scene. Volcano geology experiences new renaissance within geological and geomorphological research. Geomorphology in general experienced an unprecedent advances due to the explosion of accessibility and usage of advanced technologies such as remote sensing, GIS, shallow geophysics techniques, photogrammetry, drone technologies, dating techniques, novel experimental approaches, and sedimentology tools. The spatial modeling of variables associated with volcanoes including geochemical tracers, pyroclast types and deposits became a fundamental way of research in both active and old volcanic terrains experienced advanced landscape modification. Volcanic geomorphology is also a key science to understand the interaction between human society and volcanic eruptions to better determine the role of volcanism in the global and planetary changes on Earth impacting humanity. In this session we invite submissions showing the complexity of volcanic geomorphology and its useful aspects to understand the evolution of volcanism in various geotectonic settings and their influence on society.

Conveners: Karoly Nemeth, Ghislain Zangmo Tefogoum, Hugo Corbella, Fernando Costa, Sonia V. Silva
| Thu, 15 Sep, 09:00–10:30|Room Sala Inês de Castro-C1E
| Attendance Thu, 15 Sep, 10:30–10:45 | Display Thu, 15 Sep, 09:00–Fri, 16 Sep, 19:00|Poster area

Orals: Thu, 15 Sep | Room Sala Inês de Castro-C1E

Chairpersons: Ghislain Zangmo Tefogoum, Fernando Costa
Audrey Faral, Franck Lavigne, Bachtiar Mutaqin, Fatima Mokadem, Rahim Achmad, Rohima Wahyu Ningrum, Pierre Lahitte, Danang Sri Hadmoko, and Estuning Tyas Wulan Mei

Studying past eruptions provides a unique opportunity to improve understanding of volcanic hazards, especially in Indonesia, where volcanic eruptions are frequently deadly and destructive. As part of a recent approach to identifying and characterizing past volcanic events, we present the first reconstruction of the eruptive history of the Ternate and Tidore Islands (North Maluku, Indonesia) for the last 22,000 years cal. BP. This interdisciplinary study (geomorphology, tephrochronology, sedimentology, geochronology, geochemistry) consists of the first stratigraphic and chronological continuum from eruptive deposits established in a set of fifteen sections in Ternate, Tidore and Maitara islands. Sedimentological and geochemical data from tephrostratigraphy studies and radiocarbon dating suggest that these islands experienced at least four major explosive events from c. 22,000 to 740 years cal. BP. The earliest event is a Plinian eruption leading to the caldera formation of Telaga volcano on the island of Tidore, c. 22,000–17,500 cal. BP. The Gamalama volcano on Ternate, whose current eruptive activity is essentially strombolian or phreatomagmatic, experienced as well a pumice eruption dated to c. 18,000 cal BP. A third event dated to c. 14,500-13,000 cal. BP, associated with a succession of abundant pyroclastic deposits of scoria, pumice, and ash, is related with the phreatomagmatic eruption at the origin of the formation of the Ngade maar on Ternate Island. Although no eruptions of Kie Matubu volcano on Tidore Island have been filled out by people since their presence in the region from the 16th century, this survey identifies two late Holocene eruptions, c. 2500 cal BP and 740 cal BP. This chronostratigraphic framework from the late Pleistocene to recent eruptions in North Maluku region provides new perspectives in managing predictive and warning information for potential eruptions that may occur on these small, vulnerable volcanic islands in the future.

How to cite: Faral, A., Lavigne, F., Mutaqin, B., Mokadem, F., Achmad, R., Wahyu Ningrum, R., Lahitte, P., Sri Hadmoko, D., and Mei, E. T. W.: A 22,000-year tephrostratigraphy record of unidentified volcanic eruptions from Ternate and Tidore islands (North Maluku, Indonesia), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-37, https://doi.org/10.5194/icg2022-37, 2022.

Fernando Costa, António Alves Silva, and Madalena Fonseco

The main goal of this work is to present the first systematic inventory and scientific assessment of the geomorphosites related with the Lisbon Volcanic Complex (CVL). This geologic unit of the Upper Cretaceous, Campanian (70 to 72,6+/- 3,1 Ma) (Ferreira e Macedo, 1979), is an heritage of magmatic activity related to North Atlantic opening. The CVL covers about 150 km2 of the 9 North Lisbon region municipalities. Basalt represent 70% of the rocks of the CVL, showing the predominance of an effusive activity and a subaerial volcanism. This geological complex feature also includes other types of volcanic rocks, such as rhyolite or trachyte, or even some interspersed sedimentary rocks.

The most visible impacts on the landscape of the volcanic activity on North Lisbon region are a few traces of cones, large extensions of lava flows and pyroclastic materials, and local structures such as chimneys, necks, dykes and sills. Volcanic cones are heavily eroded however their dominant elevation remains partly preserved by compact basaltic chimneys or necks.

Some of major cones, by their panoramic views, coupled to some particular lavic features, as columnar disjunction in hexagonal prisms, are the most relevant volcanic geotouristic attractions of the North Lisbon region, by its scientific, cultural/historical, scenic/aesthetic and social/economic values, due to human perception of geomorphological landforms and processes.

A selection, fundamental description, scientific assessment and mapping of main geomorphosites, will be carried out, as a contribution to publicize the single volcanic region in Continental Portugal, in order to reduce its vulnerability, preserving this geoheritage from destructive anthropic actions. In addition, it will be suggested geotrails between geomorphosites and will be proposed instructive-educational panels, to inform about the natural processes and mechanisms that originated these volcanic landscapes.

The geomorphosites, with a recognized scientific and didactic values, include single places and areas, where volcanic rocks and structures encompasses a considerable extension, and also panoramic viewpoints, particularly the dominants volcanic cones from where a great variety of regional landforms can be observed. Also additional values, namely cultural material or immaterial and religious features, are coupled to some of these geomorphosites, particularly to the dominant landforms.

Key words: Volcanic landforms, geomorphosites assessment, landscape conservation, North Lisbon region, Portugal

How to cite: Costa, F., Alves Silva, A., and Fonseco, M.: Volcanic geomorphosites assessment in North Lisbon region, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-64, https://doi.org/10.5194/icg2022-64, 2022.

James Driscoll and Mike Hall

Unmanned Aerial Vehicles (UAVs), are increasingly used in STEM research and educational purposes as they are a cost-effective and time-efficient way to gather geospatial data, and they are a fantastic way to engage students. UAVs are utilised to survey the landscape, especially in locations where students are unable to access due to logistical or OHS reasons (even Mars!). They are also useful for students to better understand abstract concepts and to aid in conceptualisation of the ‘bigger picture’, allowing students to ‘see science for themselves’.

UAVs are a powerful educational tool if repeated missions are conducted on dynamic natural systems, such as mangrove and salt marsh systems, river environments and coastal environments since they capture both macro and micro changes in physical landscapes and ecosystems. This provides insights into the spatial and temporal evolution of the environment, and can be used to inform future management decisions. The output images, videos and surveys can be annotated and utilised as geospatial base maps for fieldwork activities. Student engagement and critical thinking skills can be enhanced by allowing the students to use the outputs pre-excursion in order to identify accessibility of field sites and possible sites for investigation.

James has been utilising UAVs for six years for a diverse range of educational purposes such as geophysical and climate change hazard identification (Hawaii and Australia), geomorphological evolution of terrestrial environments (New Zealand), changes in coastal landforms (Australia), ecosystem mapping (Australia), and production of geospatial base maps for STEM-focused fieldwork (UK, Hawaii, New Zealand and Australia). He will offer case studies and insights in how UAVs can be used to increase both visibility and purpose of geomorphology in high schools, and thus excite our next generation of geomorphologists.

How to cite: Driscoll, J. and Hall, M.: Drones and geomorphology in high schools: How to recruit the next generation of geomorphologists, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-201, https://doi.org/10.5194/icg2022-201, 2022.

Enrico D'Addario, Taraka Venkatadripathi Pattela, Lorenzo Marzini, Gianni Lombardi, Michele Amaddii, and Leonardo Disperati

The Monte Amiata is a volcano located in central Italy composed by trachytic to olivine latitic lava flows and domes emplaced between 305 and 231 ka (Pleistocene). These volcanic products, affected by saprolite alteration processes of spatially variable intensity, unconformably overlie Pliocene marine clayey sediments, as well as the Ligurian units stacked during the Northern Apennines orogeny. The Monte Amiata area has been attracting much attention from research and industry because of its economic importance in the field of geothermal energy, ore deposits and groundwater supply, hence a quite detailed geologic framework is available for this area. Instead, less efforts were made toward the understanding of the widespread gravitational processes affecting the eastern side of the volcanic edifice, often involving the transition between the volcanic rocks and the underlying sedimentary units, where many natural springs arise. The main urban agglomerations developed in this geologic setting, so buildings and infrastructures have been suffering damages caused by landslide processes over large areas. In this context, remote sensing imagery analysis, geomorphological surveys, engineering geology sub-surface investigations and ground displacement monitoring by integrating GNSS, robotic total station and geometric levelling allow us to map the main geomorphological features and infer the geometry and displacement rates of landslides occurring in the eastern side of the Monte Amiata volcano. The results suggest the occurrence of complex gravitational processes with different kinematic characteristics, state of activity and depth of the rupture surfaces. By cross-referencing the new quantitative data collected with the geomorphological evidences and the existing literature, we propose a model for the progressive dismantling of the eastern slopes of the Monte Amiata volcano caused by the interaction among complex gravitational movements affecting, at different structural levels, both the sedimentary units and the volcanic rocks. Moreover, detailed mapping of the saprolite derived by weathering of lava flows is provided and contextualised in the post-volcanic evolution of the Monte Amiata volcano.

How to cite: D'Addario, E., Venkatadripathi Pattela, T., Marzini, L., Lombardi, G., Amaddii, M., and Disperati, L.: Dismantling a volcanic edifice by deep-seated landslides: the case of the eastern Monte Amiata (Italy)., 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-611, https://doi.org/10.5194/icg2022-611, 2022.

Ghislain Zangmo Tefogoum, Armand Kagou Dongmo, David Guimolaire Nkouathio, and Merlin Gountié Dedzo

The Manengouba Volcano (MV) is one of the voluminous apparatus that composes the Cameroon Volcanic Line. It is located between Mounts Cameroon and Bambouto. It has been built between 1.55 Ma to Recent years through relevant progressive tectonic and volcanic phenomena. These events characterize the first sequence volcanism of the MV’s history. They were responsible of the building up of two fitted caldera volcanoes (Elengoum and Eboga) that compose MV. The second sequence volcanism occurred following the collapse of the Eboga caldera. It was animated by several explosive and fissural eruptions that established along the MV numerous adventive landforms. A study of the latter is of paramount importance in understanding of deposits that constitute the geomorphosites and the evolution of the geomorphology of MV. It appears from the field and laboratory investigations that the MV includes around 70 holomagmatic and hydro-holomagmatic cones. Holomagmatic cones have basal diameters between 400 and 1000 m, heights less than 100 m relative to the surrounding terrain, and external slopes greater than 50°. The majority of these cones have three main directions namely N20-N40, N60-N70 and N120-N130. These cones are composed of pyroclastic projections, in particular lapilli, bombs, blocks and scoria. These projections are of various sizes and form more or less thick layers, defining a more or less clear stratification from the base to the top, with or without granoclassing. These pyroclastites are often associated with cone bottom flows that are either compact and prismatic in structure, or compact at the base and overlain by 30-60 cm layers of scoriaceous lava. Pyroclastites are the last lava flows and are at the origin of the partial or total breaking of several cones in the MV. The hydro-holomagmatic cones are the result of phreatomagmatic explosion processes and include the Manengouba Twin Lakes (Male and Female) and a Bassin (Djeu-Seh). Their heights vary from 10 to 30 m above the surrounding terrain. The external slopes are weak (10 to 15°) contrary to the internal slopes which are abrupt (more than 60°). These cones are of major orientation SW-NE and are also composed of pyroclastic projections but with fine and coarse ashes. These cones make MV one of the most complex volcanoes of the LVC. The high number of these cones reflects the high degree of fracturing of this volcano. The stratification of different deposits provides information on the rhythm of explosions that governed the history of each cone. These cones are geomorphosites whose scientific value makes them a natural laboratory for geoeducation and research.

How to cite: Zangmo Tefogoum, G., Kagou Dongmo, A., Nkouathio, D. G., and Gountié Dedzo, M.: Investigation on the Manengouba Volcano’s geomorphosites (Cameroon): case of holo-magmatic and hydro-holomagmatic cones, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-660, https://doi.org/10.5194/icg2022-660, 2022.

Karoly Nemeth and Bo-xin Li

The Arxan-Chaihe Volcanic Field (ACVF) is a young intracontinental monogenetic volcanic field erupted since the Pliocene and located in the northeast of China. ACVF preserves at least 47 vents in a 2000 km2 area. The small-volume volcanic edifices and their eruptive products resemble typical landforms such as tuff rings, scoria cones, fissure-controlled vents, and complex, but small volcanic cones. The youngest known eruption site at Yanshan, located in the centre of the volcanic field along an elevated normal-fault bounded, SW-NE-aligned zone, dated by C14 method and yielded closely spaced but various ages of – 2040 +/−75; 1960+/−70; 1990+/−100; 1900+/−70, BP. The age variation is in good concert with the presence of nested vent complex as the reconstructed source of this eruption, forming amalgamated scoria and spatter cones with three distinct vents. The volcanic landforms are well-preserved due to the abundance of accumulated agglutinated and clastogenic lavas in their crater rims. It is apparent, that the Yanshan-event produced an extensive and multi-tephra pyroclastic succession, that formed an ash plain just east of the cone complex. The extend of the ash blanket revealed to be far more than previously thought as recent SENTINEL imagery marks ash coverages - even in patchy mode - well over 20-km from the vent. Large rafted, welded cone blocks, mostly in the SW opening of the main cone where a major lava flow broke out, create strong surface ruggedness and young volcanic surface features in the vicinity of the vents. The lava flows (mostly rubble, slabby pahoehoe) apparently filled a north-westward steeply inclined rift shoulder and reached the Halaha River valley within 8 km, in about 230 m elevation drop. When the lava flows reached the Halaha River valley floor, in the combination of sudden slope angle changes of the terrain and the wet valley floor produced a spectacular lava tumuli field. Present day lacustrine systems are inferred to be formed after the major lava flows from the Yanshan vent diverted the fluvial channels about 2000 years ago. Analysing of SENTINEL satellite imagery, it is evident, that the Halaha River lava field is far more complex, and not exclusively derived from the Yanshan vents. A large crater (~1.1-km across), Dahei Gou just about 5-km to the SW from Yanshan shows young lava lake within its crater and slightly older lava outflow toward the Halaha Valley on SENTINEL imagery. Lava flows are seemingly diverted and partially “invaded” the Dahei Gou lava flow system in the axis of the Halaha Valley, marking a relative chronology of volcanic events inferred to be driven by a SW to NE directed fissure opening that likely took place over weeks or even years based on the lava flow surface patterns. In addition, a 6.5-km long fissure connects the Dahei Gou and Yanshan vents. This volcan-morphological study reveals an important volcanic hazard this region and making the youngest volcanic event a key eruption scenario future volcanic hazard planning of the region needs to observe.

How to cite: Nemeth, K. and Li, B.: Complex lava flow evolution reveals prolonged fissure-fed eruption scenario for the youngest (~2000 BP) eruptive event of the Arxhan-Chaihe Volcanic Field, Inner Mongolia in NE China, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-692, https://doi.org/10.5194/icg2022-692, 2022.

Display time: Thu, 15 Sep 09:00–Fri, 16 Sep 19:00

Poster: Thu, 15 Sep, 10:30–10:45 | Poster area

Chairpersons: Fernando Costa, Ghislain Zangmo Tefogoum
Daniel O'Hara, Liran Goren, Benjamin Campforts, and Matthieu Kervyn

Volcanic edifices are dynamic landforms whose morphology encodes the long-term (thousands to millions of years) interaction between construction and erosion. Short-term episodes of volcanic activity that cumulatively build topography compete with long-term erosive processes associated with climate and mass wasting to degrade edifices, generating a variety of morphologies from simple, cone-like edifices to complex, non-axisymmetric volcanoes. However, separating the signatures of these processes using topography remains elusive as both volcanic and climatic processes are often spatially-heterogeneous and temporally-varying. Despite this, disentangling edifice morphologic histories provide new avenues to better discern an edifice’s volcanic record, assess potential hazards, and quantify the role of climate in landscape evolution.

Here, we aim to understand the long-term interaction between volcanic and erosional processes in driving edifice morphology using numerical landscape evolution modeling and comparing modeled landscapes to the morphology of the Kaua`i shield volcano. Kaua`i has been built over the past 5 Myr by series of lava flows that have non-uniformly altered both topography and surface erodibility. Coupled with this, a strong precipitation gradient across the island has influenced basin-scale erosion rates, impacting drainage development and making Kaua`i a natural laboratory to test the effects of spatially- and temporally-varying construction and degradation processes.

We analyze the interaction of these processes by first characterizing the impacts of lithology and precipitation gradients on edifice morphologies over 5 Myr timescales by employing the TopoToolbox Landscape Evolution Model. Starting with an initial, simplified edifice geometry, we test the effects of both singular and multiple parameter gradients through space and time over a broad parameter space. We then quantify edifice degredation and evolution using a series of metrics that include topographic hypsometry, basin geometries, drainage density, and , showing that such parameter gradients create asymmetric landforms with spatial heterogeneities related to the geometry and configuration of basins and channel networks. Afterwards, we consider edifice morphologic evolution within the framework of Kaua’i. By constraining the spatiotemporal model parameter configurations with the geologic and precipitation data of the volcano, and comparing modeled landscapes to the current morphology of Kaua’i, we determine likely parameter ranges that contribute to its evolution.

How to cite: O'Hara, D., Goren, L., Campforts, B., and Kervyn, M.: The impact of strong precipitation and lithologic gradients on the evolution of post-eruption volcanic surfaces, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-456, https://doi.org/10.5194/icg2022-456, 2022.