Basaltic lava (late March 2021 eruption in Geldingadalur Valley, Rekjanes Peninsula, Iceland) 3
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Iceland is a volcanic island in the North Atlantic Ocean between Britain and Greenland. It is situated on the Mid-Atlantic Ridge, along which the North American Plate and the Eurasian Plate separate and new oceanic crust forms. Seismicity in the area is due to subsurface magma movement from hotspot (mantle plume) activity, as well as seafloor spreading (= tectonic divergence). Magma reaching the surface results in volcanic eruptions. Some famous eruptions in Iceland include Laki (1783), Surtsey (1963-1967), Eldfell (1973), Hekla (1991, 2000), Eyjafjallajökull (2010), and Grimsvötn (2011).
Starting 19 March 2021, a basaltic lava flow eruption began in the Geldingadalur Valley, next to the Fagradalsfjall Volcano in southwestern Iceland's Reykjanes Peninsula. This followed a swarm of about 50,000 earthquakes that occurred during the previous month. The eruption reportedly started as a fissure eruption - lava was spewed from an extensive crack in the ground. This evolved into a short chain of spatter cones, one of which ended up being larger than the others (= main cone), with more energetic activity. Two smaller spatter cones next to the main cone evolved into a single larger structure that ended up having fairly energetic lava fountaining. Spatter cones are small to very small, steep-sided volcanic cones formed by the accumulation and solidification of blobs of lava that sputtered from a vent. They are usually basaltic in composition.
Seen here is the upper surface of a lava sample from the lava flow surrounding the new spatter cones. The lava flows consist of pahoehoe lava and (apparently) slabby pahoehoe. This specimen is composed of highly vesiculated tachylite and sideromelane. Anchored threads of basaltic glass ("Pele's hair") are present in some stretched vesicles. The hint of rainbow iridescence in the photo is real - the glassy exteriors of juvenile lava samples often have slightly iridescent surfaces.
Locality: periphery of juvenile lava flow (collected 23 March 2021) produced by spatter cones in Geldingadalur Valley, Rekjanes Peninsula, southwestern Iceland
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FagradalsfjallFagradalsfjall je islandská aktivní štítová sopka na poloostrově Reykjanes, ve vulkanickém komplexu Krísuvík, asi 40 km jihozápadně od Reykjavíku. S výškou 385 m n. m je nejvyšší horou poloostrova. Sopečná erupce, která stále pokračuje, začala 19. března 2021 v Geldingadaliru jižně od Fagradalsfjallu. .. pokračovat ve čtení