|Volcano Calendar 2017
: We're proud to present our 2017 volcano calendar: 13 different and attractive images of volcanoes, volcanic landscapes and phenomena taken during volcano tours over the past few years.
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Illustrated Volcano Glossary
The most common type of volcanic rock, with a relatively low silica content and typically erupted at shield volcanoes.
Basalt is the usually hard and black volcanic rock formed from (liquid) balsalitc lava. Balsaltic lava contains less than about 52 percent silica (SiO2) by weight. Because of its low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can quickly and easily flow more than 20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns, although basaltic lava fountains and fissure eruptions, however, still can be hundreds of meters tall. Basaltic lava is erupted at temperatures between 1100 to 1250°C.
Basalt is by far the most common volcanic rock type. Basaltic magma is formed by partial melting of material from the upper mantle, and and is therefore typical for volcanism at hot-spots and at rift-zones. In these areas, upwelling of the mantle (either caused by a rising mantle plume underneath hot-spots, or by a divergent plate boundary at mid-ocean rift zones) decreases the pressure of the hot rock and therefore causes (partial) melting.
Oceanic crust and submarine volcanoes consist largely of basalt, because most of them are formed at rift-zones (all ocean floor) or hot-spots. Among subaerial volcanoes, basaltic lava is primarily found at shield volcanoes.
Basaltic lava flows can be subdivided into two end-member structural types, according to their flow surfaces:
-- Pahoehoe lava - smooth, billowy, or ropy surface.
-- A'a' lava - fragmented, rough, sometimes spiny, or blocky surface
More on VolcanoDiscovery:
Ubinas activity updates
: The most frequently active volcano in Peru entered a new eruptive phase in 2014. Updates and news are regularly posted on this page.
Latest quakes in Greece
: Greece has a lot of earthquake activity, but most of them occur around the margin of the Aegean microplate. The Cycladic islands are located in its center and therefore seismically comparably quiet.
: Our signature tours for small groups - we take you to discovery volcanoes and volcanic areas from close with an expert in their field. These tours have a broad mix of activities and interests from photography, walking, study travel, nature & culture.