Shield volcano
A shield volcano is a large
volcano with shallow-sloping sides. The name derives from a translation of "
Skjaldbreiður", an Icelandic shield volcano whose name means "broad shield," from its resemblance to a warrior's shield. Shield volcanoes are formed by
lava flows of low
viscosity — lava that flows easily. Consequently, a volcanic mountain having a broad profile is built up over time by flow after flow of relatively fluid
basaltic lava issuing from vents or fissures on the surface of the volcano. Many of the largest volcanoes on Earth are shield volcanoes. The largest is
Mauna Loa on the Big Island of
Hawaii; all the volcanoes in the
Hawaiian Islands are shield volcanoes. Shield volcanoes can be so large that they are sometimes considered to be a
mountain range, such as the
Ilgachuz Range and the
Rainbow Range, both of which are located in
Canada. These shield volcanoes formed when the
North American Plate moved over a
hotspot similar to the one feeding the
Hawaiian Islands, called the
Anahim hotspot. There are also shield volcanoes, for example, in Washington, Oregon, and the
Galapagos Islands. The
Piton de la Fournaise, on
Reunion Island, is one of the more active shield volcanoes on earth, with one eruption per year on average.
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Volcan bouclier
Un volcan bouclier est un type de
volcan effusif. Il s'agit, en général, d'un vaste volcan cônique avec, en son centre, un large
cratère rempli de
lave fluide, appelé
lac de lave. Un volcan bouclier peu s'éteindre et être remplacé par un large trou ou par un
lac acide. En éruption, un volcan bouclier peut devenir très potent, voire dangereux s'il rejette des cendres et de l'acide dans l'atmosphère.
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Schildvulkan
Wulkan tarczowy
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Schildvulkaan
In tegenstelling tot de
stratovulkanen, zijn schildvulkanen vrij rustig wanneer ze uitbarsten. Doordat de
lava van deze
vulkanen relatief vloeibaar is zijn uitbarstingen zelden catastrofaal. Schildvulkanen hebben, juist doordat de lava zo vloeibaar is, maar zeer flauwe hellingen. De steilheid bedraagt dan ook maar enkele graden. Alleen rond de krater kan het wel tot 10 graden oplopen. De schildvulkanen hebben meestal wel een grote omvang omdat de lava die eruit stroomt heel langzaam koelt en dan hard wordt.
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