Types of Volcanoes Present on Earth
Volcanoes get their name from the Greek word Vulcano. "To the ancient Greeks, Vulcano was Hiera Hephaistou…to the ancient Romans it was the home of the forges of Vulcan; to both Vulcano was the lair of the god of fire" (Bullard 1984). Since then the myths have all gone but the name Vulcano has remained as the symbol for all volcanoes.
"A volcano is both the place and opening from which molten rock, solid rock or gas issues from a planetary interior" (Scarth 1994). It is also defined as the mountain or hill built up around the opening at the surface by an accumulation of the ejected materials.
Sources of molten rock below the surface of the earth is called a magma reservoir, magma being the term given to molten or semi-molten rock below ground level. The magma travels up to the surface from the magma reservoir through conduits and emerges at the surface through volcanic vents (Fig 1).
If the eruption happens to be explosive the magma is ejected from the vent as a dense cloud of volcanic ash, bombs and other forms of pyroclastic rock. When the eruption is non-explosive, it is said to be effusive and the magma issues from the volcano as lava.
In the following paragraphs the different types of volcanoes that are present on Earth will be looked at and discussed. Such as the lava domes, calderas and shield volcanoes.
Types of Volcanoes
Lava Domes
Fig 2: Schematic representation of the internal structure of a typical volcanic
One type of volcano is the lava dome. These are formed by relatively small, round masses of lava too thick to flow any great distance. As a result on extrusion, the lava piles over and around its vent. The dome grows largely by expansion f...
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...early vertical walls facing into a central flattish floor" (Brown 1970). They are so beautiful that it is hard to imagine that they have been produced by some of the most catastrophic events on Earth. Many develop within the space of a few hours. Huge volumes of material are erupted and huge volumes of material sink into the crust. At least ten caldera forming eruptions in the past 10,000 years have been ejected more than 50km of ash and pumice. Calderas fortunately are not formed very often and only two or three are created every century.
Hydrovolcanic landforms
Hydrovolcanic landforms develop when an external source of water interacts with magma approaching the Earth's surface. The large areas covered by water, ice, snow, the frozen ground, abundant precipitation, subsurface qualifiers, all combine to ensure that some interaction between water and magma.
Magmas in island arc settings consist primarily of components from two different origins, the slab component, and the mantle wedge. The mantle wedge may melt due the descent of the slab, giving the main portion of the non-slab component. The slab component is derived from the subducting slab as it descends. This may consist of melting of the crustal portion of the slab, but also melting of the mantle wedge due to addition of water driven off the slab. Since the descending slab is composed of old, cold oceanic crust, there is a slight paradox in the idea of melts forming from it. However, frictional heat, as well as the heat of the underlying mantle, can drive hydrous fluids off the slab. (Machado, Chemale Jr., Conceição, Kawashita, Morata, and Van Schmus, 2003; Kimura and Yoshida, 2006).The addition of water to the mantle wedge results in the lowering of melting temperatures, allowing melts to be formed at much lower temperatures than might otherwise be expected. Also, the circulation of hot fluids allows materials dissolved in them to migrate upwards ...
Volcanoes have always been a mysterious wonder of the world. Volcanoes have shaped the landscape and the very ground that we all live on. People have written stories of their disastrous eruptions, and painted their marvelous shapes on canvas. The essay will outline some of the more famous volcanoes and how they have impacted are history. Mount Vesuvius that destroy the great city of Pompeii, Krakatoa they spewed deadly ash on small village town, and Mount St. Helen, the only volcano in my own country to every erupt during my own time period.
Basalt forms due to the partial melting of the layer of the mantle called the asthenosphere. The asthenosphere is the plastic zone of the mantle beneath the rigid lithosphere. Mantle plumes coming from the mesosphere can cause the asthenosphere to melt with heat or even if pressure decreases, which is called decompression melting (Richard 2011). The magma that forms from this melting is mafic magma that solidifies once it reaches the earth’s surface and cools quickly. The above process mainly occurs mainly during intraplate igneous activity which is the main explanation for volcanic activity that occurs a long distance away from a plate boundary. If the tectonic plate above the mantle plume is moving it can create a string of volcanic activity such as in Hawaii. See Fig 2.
Volcanoes. The naturally forming landforms that can look remarkably beautiful. Gentle slopes, or high rising heights with snow caps and greenery that seems to attract many tourists and sightseers around the world. These magnificent landforms can also cause major destruction and can produce forces that can explode, burn, and create a great deal of damage. Two of these extravagant wonders of the world is the Mount Saint Helens composite volcano in Washington, US, and the Mauna Loa shield volcano in Hawaii, US. These landforms have a eruption history of many colors. One has a great power in eruption, but another has a eruption that is quiet and gentle. In comparing these two volcanoes there are many likes, and dislikes, to consider. So the following
Stories about volcanoes are captivating. Myths come in different versions, but all of them are capable of capturing yours, and everybody’s imagination.
Super volcanoes are formed when magma rises from the mantle to create a scorching reservoir in the Earth's
Magma is a hot liquid made of melted minerals. Minerals can form crystals when they are cool. Igneous rock can form underground, where the magma cools. slowly. Or, igneous rock can form above ground, where the magma cools.
Volcanoes are one of natures most interesting and dangerous phenomenons. The way volcanoes operate can be understood, on a basic level, by just some simple physics and chemistry, this paper will investigate and explain some of the basic physics that govern the behavior of volcanoes.
comes up in a crack in the Earth’s crust, it does not come to the surface, but
There are four major types of study that make up a volcanologist or team of volcanologists. These include physical volcanologists, geophysicists, geodesic volcanologists and geochemists (What does a volcanologist do?, n.d.). Physical volcanologists study the actual processes that make up a volcanic eruption. They also study the deposits made during the eruption. Where the rocks from the eruption were distributed and what their makeup is.
Volcanoes can cause damage by spewing lava, but earthquakes before the eruption can also cause damage. These earthquakes open fissures and let magma out to the surface. When the magma exits these fissures, streams of lava up to hundreds of feet can shoot into the air. The picture below shows the lava erupting from the fissures created by the earthquakes in...
Igneous rocks are formed from the ejection of earth’s volcanoes. Deep down inside earth’s mantle there lies hot magma. Magma is molten rock that is kept below the surface. This mixture is usually made up of four parts: a hot liquid substance which is called the melt; minerals that have been crystallized by the melt; solid rocks that have made themselves tangled in the melt because of loose materials, and finally gases that have become liquid. Magma is created by an increase in temperatures, pressure change, and a alter in composition. When this magma is ejected from earth’s crust it earns a new name called lava. The lava hardens and becomes an Igneous rock.
The earliest outcropping volcanic deposits date back to about 25,000 years ago. The lavas observed at a -1125 m bore-hole are about 0,3-0,5 million years old. It is known for the first eruption of which an eyewitness account is preserved, in 79 AD. Geologically, Vesuvio is unique for its unusual versatility. Its activity ranging from Hawaiian-style release of liquid lava, fountaining and lava lakes, over Strombolian and Vulcanian activity to violently explosive, plinian events that produce pyroclastic flows and surges.
The interior structure of the earth is made up of crust, the mantle and core (inner core and outer core). Earthquakes occur on the crust. Crust forms the external layer of the earth surface. On the crust, the plate tectonics forces are in charge of causing the abrupt earth movements. Due to the existence of an immense temperature and concurrent pressure difference in the outer layer and inner layer of the earth, convection currents occur at the mantle. This energy results from overwhelming decomposition of radioactive substances contained by the rocks found at the interior of the earth. The developed convection currents lead to movement of lava; cold lava finds its way to the interior of the earth crust, while the molten lava which is generally hot, leaves the interior of the earth to the outside of the earth crust. These kinds of circulations occur at different locations of the earth surface and consequently results in segmentation of the earth due to movement in different directions.