COMPARE AND CONTRAST HOW MAGMAS ARE GENERATED AT MID-OCEAN RIDGES AND SUBDUCTION ZONES. According to Middlemost (1988)’s basic definition, magma is a heated rock-forming substance that is created within a planet and exists only below Earth. When magma escapes to the Earth’s surface and is extruded, they are known as lavas. Grotzinger and Jordan (2010) suggests that magma mainly comes from the asthenosphere- the upper part of the mantle. Magmas are usually generated when rocks are under the right temperature and pressure conditions to undergo partial melting (Grotzinger and Jordan, 2010). At high temperatures and low enough pressures, rocks would reach its melting point easily. It is known for a fact that temperature increases with depth …show more content…
Subduction zone magmas are formed by convergent plate boundaries between oceanic-continental plates or oceanic-oceanic plates (at least one tectonic plate has to be oceanic) (see Fig.1). According to Grotzinger and Jordan (2010), when the oceanic lithosphere gets subducted, there is fluid induced melting occurring to the mantle wedge. Therefore, this generates magmas of varying composition. From Prichard et al.’s findings, mid-ocean ridge magmas are usually basaltic in composition whereas subduction zone magmas are andesitic and more silicic. Subduction zone magma compositions also depend on the materials being subducted. Hence, in terms of chemical composition, the subduction zone magmas and are definitely more varied compared to the mid-ocean ridge magmas. Subduction zone magmas range from basaltic to rhyolitic- with andesitic magmas being the most common (Grotzinger and Jordan, 2010). Fig.2 Geothermal gradient varying in different geological settings: also showing the solidus for MOR and subduction zone mantle rock MAGMA GENESIS Middlemost (1988) states that in the mantle at depths between 60-250 km (i.e. the low-velocity zone), magma can be generated through either of the 3 ways; when you add
This lab uses earthquake data to construct profiles of two convergent boundaries: the Tonga Trench and the Peru-Chile Trench. Where two tectonic plates converge, if one or both of the plates is an oceanic lithosphere, a subduction zone will form. When crust is formed at a mid-ocean ridge, it is hot and buoyant meaning it has a low density. As it spreads away from the ridge and cools and contracts, or becomes denser, it is able to sink into the hotter underlying mantle. When two oceanic plates collide, the younger of the two plates, because it is less dense will ride over the edge of the older plate. The density of the
Anpother factor that can have an impact on the level of hazard posed by a volcano is the type of plate margin on which it occurs. Volcanoes occuring at constructive plate boundaries are usually much less violent than those occuring at destructive plate boundaries. This is because the magma produced by plates moving apart is Basic, and therefoe has a low viscosity, allowing it to flow easily. The lava is produced from a central vent or fissure and erupts regularly but not usually violently. Also,constructive plate boundaries are often found under the sea and create submarine volcanoes, such as along the Mid-Atalntic ridge, so pose few threats to humans. As a result, the hazards posed by volcanoes at constructive plat eboundaries is relatively low. However, the subduction of one plate under another at destrctive plat eboundaries can form an acidic magma chamber, due to the build up of intense heat. Acidic magma is very viscous and resisitant to flow, meaning that there is often a huge build up of pressure, which can result in very violent and dangerous eruptions involving ash and pyroclastic flow. This can pose a a serious hazard. Pyroclastic flowsa are extremely dense, containing toxic gases at very high temperatures, and can move at speeds over 100km/h. The consequences of such an unpredictable hazard can be extremely seruous
Volcanoes can be found throughout the entire world and are formed when there is a rupture in the mantle of the Earth's crust. This effect allows the output of volcanic lava, ash, and various types of gases. These tectonic plate breaks are normal, the planet Earth is divided into 17 tectonic plates and consistently move against each other forming shifts from low to high intensity. It can cause displacement of earth or water.
The new volcanic material welling up into the void, which forms a ribbon of new materials and breaks down its center gradually, when the plates move apart from the axis of the mid-oceanic ridge system. Therefore, every separating plate accretes one half a ribbon of new lithosphere, and, thus, a new surface is added (Pitman, W.C, 2007). The process is continuous, and separation is always happening at the
The heavier oceanic plate is being pushed under and melted so that it will rise up the lithosphere as magma and gasses to cause an eruption
The youngest of these rocks are dated at about 220,000 years ago. Rhyodacties and quartz latites in the modern caldera area extruded from about 320,000 years ago to 260,000 years ago, and then silica-rich rhyolites at Glass Mountain northeast of the caldera erupted from about 210,000 years ago to 80,000 years ago. The scattered distribution of the initial mafic eruptions indicates that they were erupted from the mantle, while the slightly younger domes and flows were from a deep-crustal source. The youngest rhyolite eruptions erupted at the northeast rim of the caldera at Glass Mountain and were the first activity of the silicic Long Valley magma chamber (Bailey, et. al., 1989).
Most of Earth’s volcanoes are located in the _______________ around the Pacific Rim just beyond the oceanic trenches, where magma, which is less dense than the
The youngest oceanic crust is located along the mid-ocean ridges where new crust is formed when the old crust is pushed away from mid – ocean ridges as a result of the seafloor spreading.
Silicious lava, forced up from deep down below. Soda trachytes extruded in a highly viscous state, building the steep-sides mametons we see in Hanging Rock. And quite young, geologically speaking. Barely a millions years old. (Greene, 11)
The Earth’s outer crust is made up many tectonic plates that move over the surface of the planet. When the plates come collide, volcanoes will form sometime (National Ocean Service). Volcanoes can also form in the middle of a plate, where magma rises upward until it erupts on the sea floor, at what is called a “hot spot” (National Ocean Service). A hot spot is a plume of magma or molten rock that rises from within the Earth then reaches the surface forming underwater volcanoes which may grow tall enough to
Convection currents may bring magma to the surface at diverging boundaries. Sedimentary rocks from the ocean floor gets pushed down to the mantle at convergent boundaries. The crust soon melts and rises to the surface creating igneous rock. Typically mountain ranges are metamorphic rock, maybe our mountains are.
A period of volcanism resulted in igneous intrusions within the Raton Basin-Sierra Grande Uplift Province that was sourced from the upper mantle about 26. 6 billion years ago and is associated with parallel dikes and sills (Higley, 2007). Igneous rocks are common within the Raton Basin and include Tertiary dikes and sills that range in age from 6.7 to 29 5 million years ago (Flores and Bader, 1999). One of the main differences between dikes and sills is that dikes are longer lived magma conduits and sills are features that form when magma is in neutral buoyancy with the surrounding rock (Rooper et al., 2006). These volcanic events are associated with hydrothermal alteration of coal within the basin (Higley, 2007).
Higher temperatures cause atoms to spread out and decrease in density, so magma at higher temperature is less viscous and will flow more easily
It is minimal realized that lying underneath one of The United States biggest and most beautiful National Parks - Yellowstone Park - is one of the biggest "super volcanoes" on the planet. Every year, a huge number of guests come to respect the hot springs and fountains of Yellowstone, the Nation's first national park. Few are mindful that these miracles are powered by hotness from a vast repository of incompletely liquid rock (magma), simply a couple of miles underneath their feet. As this magma-which drives one of the world's biggest volcanic frameworks climbs, it pushes up the Earth's hull underneath the Yellowstone Plateau.
The continental crust consists of igneous and sedimentary rocks. The oceanic crust consists of the same with a substantial layer of sediments above the rock. The crust covers the outer ridged layer of the earth called the lithosphere. The lithosphere is divided into seven main continental plates. These continental plates are constantly moving on a viscous base.