About 80% of volcanoes occur at convergent plate.
About 80% of volcanoes occur at convergent plate.
Volcanoes are simply the vents in the earth's surface through which magma flows. Important constituents of magma are water and dissolved gases, called volatile constituents. Magma is a solution of these constituents and silicate minerals, confined together by the pressure of the overlying rocks, so the volatiles don't escape. Magma rising to the surface through cracks or fissures in the crust allow the volatiles to be released with explosive force, due to the sudden drop of pressure. This eruption causes lava to be fragmented into various sizes, shapes and textures. The violence of the eruption and the degree of fragmentation depend largely upon the chemistry of the magma. Basaltic lavas (those containing mainly plagioclase feldspar and pyroxene) tend to flow with less violence and force than felsic (poor in iron and magnesium with abundant quartz and feldspar), volatile-rich viscous lavas. Lava extruded on the surface form extrusive igneous rocks, such as basalt, andesite, rhyolite and obsidian. Igneous rocks that crystallize beneath the surface are intrusive, such as granite. Volcanoes play a vital role in expelling heat and energy from the interior. However, they are not evenly distributed. Most of them form in the vicinity of plate boundaries. The fragmentary volcanic rock materials expelled by a volcano are termed pyroclasts. Pyroclasts include volcanic ash, dust, bombs, volcanic tuffs and breccias.
what are some advantages and disadvantages of volcanoe?
There is a former volcano in my country but i am not sure which type it was. as i observed from the landscape i guess it was Shield Volcano
summary and what we know of hese active or inactive volcanoes is their way to prevail in time and give surprises, according wing amount of accumulated gases and lava material can launch sometime disasters ocacionados the environment, landscape and system thereby biotic human lives, as the case of nevado del Ruiz Volcano, the November 13, 1985 by deleting the population of tolima armorer river bed of chinchina leaving thousands dead
I now begin to understand the various earth-related calamities being reported by different sections of the world
Volcanoes contributed alot to the shaping of the earth's plateau
I really love this course!
volcanoes may have help to create life on Earth and they provide nutrient to the soil.
This is very interesting course for us that are working in climate and weather services. Upon the completion of this course, the knowledge and skills gained will be used to other staff members within the Liberia Meteorological Service.
An active volcano occurs when magma (molten rock) reaches the earth\'s surface through a crack or vent in the crust. Volcanic activity can involve:
the extrusion of lava on the surface,
the ejection of solid rock and ash, and
the release of water vapor or gas (carbon dioxide or sulfur dioxide).
Volcanoes commonly occur near plate boundaries where the motion of the plates has created cracks in the lithosphere through which the magma can flow. About 80% of volcanoes occur at convergent plate boundaries where subducted material melts and rises through cracks in the crust. The Cascade Range was formed in this way.
Volcanoes can be classified according to the type and form of their ejecta. The basic types are:
cinder cones, and
Composite volcanoes are steep-sided, symmetrical cones built of multiple layers of viscous lava and ash. Most composite volcanoes have a crater at the summit which contains the central vent. Lavas _flow from breaks in the crater wall or from cracks on the_flanks of the cone.
Mt Fuji in Japan and Mt Ranier in Washington are examples of composite volcanoes.
Shield volcanoes are built almost entirely of highly _fluid (low viscosity) lava _flows. They form slowly from numerous _flows that spread out over a wide area from a central vent. The resultant structure is a broad, gently sloping cone with a profile like a warrior\'s shield.
Mt Kilauea in Hawaii is an example of a shield volcano.
Cinder cones are the simplest type of volcano. They form when lava blown violently into the area breaks into small fragments that solidify and fall as cinders. A steep-sided cone shape is formed around the vent, with a crater at the summit.
Sunset Crater in Arizona is a cinder cone that formed less than a thousand years ago, disrupting the lives of the native inhabitants of the region.
Lava domes are formed when highly viscous lava is extruded from a vent and forms a rounded, steep sided dome. The lava piles up around and on the vent instead of _flowing away, mostly growing by expansion from within. Lava domes commonly occur within the craters or on the_flanks of composite volcanoes.
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