Original paper

Morphology of lava tumuli from Mendoza (Argentina), Patagonia (Argentina), and Al-Haruj (Libya)

Németh, K. Haller


The studied volcanic fields are associated with compound flows near the vents that are characterised by a tube network, sky lights, ephemeral vents and tumuli. During discontinuous activity discrete, channel-fed aa flow units in near-vent position often form fan-shaped flow fields that resemble vents effused by spatter-fed or clastogenic lava. These flows resulted from (a) reconstitution of fountain-generated spatter around vents by syn-depositional agglutination and coalescence, and (b) syn-eruptive collapse of rapidly grown spatter and scoria. In the studied lava shields three types of tumuli have been identified: (1) lava-coated tumuli, (2) upper-slope tumuli in near-source regions (both dominated in Libya), and (3) flow-lobe tumuli in the distal areas (in all studied areas). The widespread flow-lobe tumuli in the studied fields confirm the general agreement of low lava-supply rates. Flow-lobe tumuli are interpreted to have been supplied with magma from tubes that originate in overflow from and through flank fissures connected with the lava lake of shield volcanoes.