Identification of topographic fingerprints of eruption environments: Geomorphometric evidence from volcanoes of the Reykjanes Peninsula, Iceland P23C-1946 The geomorphometry of volcanoes provides important information on the geologic evolution of planets. Therefore, constraining the topographic characteristics of terrestrial volcanoes is an important step for comparative planetology. Here we resolve geomorphometric fingerprints of volcanic edifices formed in subaerial, submarine and subglacial environments by focusing on volcanoes of the Reykjanes Peninsula, Iceland. The Reykjanes Volcanic Belt connects the Reykjanes midoceanic spreading ridge with the Western volcanic zone. It consists of four volcanic systems that display a variety of pristine Quaternary submarine, subglacial and subaerial volcanic edifices. 35 edifices were chosen for quantitative characterization using the IS 50V digital elevation model (20m/pixel). The edifice boundaries were delimited by concave breaks in slope around their bases and edifices were grouped according to slope, size and shape. A division based on slope values proves successful in discriminating subaerial edifices from subglacial and submarine edifices. Subaerial shields have average slopes between 2.8 °-6.5 °, which is at least 6 ° less than the average slopes of submarine and subglacial edifices. Moreover, the shields can be sub-divided into tholeite (2.8 °-4.6 °) and picrite (5.3 °-6.5 °) shields based on average slope. Submarine and subglacial edifices cannot be distinguished from each other by average slopes, and were grouped together in a submarine and subglacial class. This class was sub-divided into 3 groups based on their volume and suggests an evolutionary growth trend starting with small elliptical, linear ridges (~2*10-3-7*10-3 km3) to flat topped, table-shaped mountains (~100*10-3 -640*10-3 km3), with an intermediate growth stage (~10*10-3 – 80*10-3 km3) of very variable and irregular complex edifices. Further analysis of topographic profiles, slope frequency and elevational slope development, show that it is possible to resolve individual land elements based on break in slope, such as lava cap, hyaloclastite apron, hyaloclastite slope and hyaloclastite summit. The boundary between hyaloclastite breccia and lava cap represents a passage zone that marks late-stage subaerial lava-fed deltas and is clearly defined by convex breaks in slope. Large elevation changes in the passage zone is diagnostic of lava deltas emplaced in a glacial environment, and thus mapping of elevation changes of convex breaks in slope is a potential tool for distinguishing big table-shaped volcanic edifices emplaced in a submarine or subglacial environment. This study shows that volcano morphometry can be used to obtain information on processes operating during volcano construction, its eruption environment and the resulting evolutionary growth trends. A significant advantage of this method is its application for remote and inaccessible areas such as submarine or subglacial environments as well as extraterrestrial planets. Moreover, the break in slope delimitation of edifice bases and the possibility of resolving individual landform elements makes this geomorphometric analysis directly applicable for advanced mapping techniques such as object-based image analysis.
Gro B Pedersen1, 2, Pablo Grosse3 1. Earth Sciences, Nordic Volcanological Center, Reykjavik, Iceland; 2. Earth Sciences, Aarhus University, Aarhus, Denmark; 3. CONCINET, San Miguel de Tucuman, Argentina