What type of magma is created at mid-ocean ridges quizlet?
How is magma produced at Mid-Ocean Ridges and at Hot Spots? Magma with mafic composition erupts 1) basaltic lavas. As it cools and crystallizes the intermediate point takes away elements changing the composition to andesitic. Remaining melt is enriched with silica (felsic).
How is magma created at mid-ocean ridges?
Mid-ocean ridges are considered the planet's largest magmatic system. At divergent plate boundaries, magma is generated by decompression melting of upwelling mantle. Melts are focused as they ascend through the upper mantle and lower crust and collect beneath the ridge axis in elongate melt lenses.
Which lava is common at mid-ocean ridges?
basalt The lava produced at the spreading centers is basalt, and is usually abbreviated MORB (for Mid-Ocean Ridge Basalt). MORB is by far the most common rock type on the Earth's surface, as the entire ocean floor consists of it.
Which forms at mid-ocean ridges?
basalt Mid-ocean ridges occur along divergent plate boundaries, where new ocean floor is created as the Earth's tectonic plates spread apart. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt.
Why does melting occur along mid-ocean ridges?
As mantle ascends beneath the mid-ocean ridge, less and less rock lies above it, so large pressure changes occur, which leads to melting. The melt is less dense than the solid, and rises to the surface to form the oceanic crust.
What will be the composition of magma that forms as oceanic crust partially melts?
The rising subduction-zone magma is probably basaltic in composition and is formed by the partial melting of mantle rocks.
What is formed at mid-ocean ridges as magma rises and cools?
This bubbled-up magma is cooled by frigid seawater to form igneous rock. This rock (basalt) becomes a new part of Earth's crust. Mid-Ocean Ridges Seafloor spreading occurs along mid-ocean ridges—large mountain ranges rising from the ocean floor.
Do mid-ocean ridges have magma chambers?
Most mid-‐Ocean ridge magma chambers are mostly small and mostly mush (lots of crystals), most of the ome.
What is basaltic magma?
Basaltic (or mafic) magma predominates in nonexplosive volcanic eruptions. It is a high-temperature magma (1,200 °C (about 2,200 °F)) characterized by flowing lava, and it is made up of about 45–55 percent silica (SiO2) by weight.
What occurs at mid-ocean ridges quizlet?
Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics.
What is the source of magma for seafloor spreading?
Seafloor spreading and other tectonic activity processes are the result of mantle convection. Mantle convection is the slow, churning motion of Earth's mantle. Convection currents carry heat from the lower mantle and core to the lithosphere. Convection currents also “recycle” lithospheric materials back to the mantle.
What happens when magma comes out of the ocean ridge?
When the magma cools it forms basalt, the planet's most-common rock and the basis for oceanic crust. It has long been assumed that the composition of magmas erupting out of mid-ocean ridges is altered when minerals that form during cooling sink out of the remaining liquid, a process called fractional crystallization.
Which type of magma forms at the mid ocean ridges or at hot spots under the ocean crust and is high in iron and magnesium but is low in silica?
basalt The basalt of the oceanic crust formed at mid-oceanic ridges, so it is known as "MORB" – Mid-Ocean Ridge Basalt.
What is the basaltic magma?
Basaltic (or mafic) magma predominates in nonexplosive volcanic eruptions. It is a high-temperature magma (1,200 °C (about 2,200 °F)) characterized by flowing lava, and it is made up of about 45–55 percent silica (SiO2) by weight.
Why does magma rise at a mid-ocean ridge?
Beneath a typical mid-ocean ridge, mantle material partially melts as it rises in response to reduced pressure. This melted rock, or "magma", may collect in a reservoir a few kilometers below the seafloor, awaiting eruption.
Why does melting occur at mid-ocean ridges?
As mantle ascends beneath the mid-ocean ridge, less and less rock lies above it, so large pressure changes occur, which leads to melting. The melt is less dense than the solid, and rises to the surface to form the oceanic crust.
How is andesitic magma formed?
Andesitic magma is formed through wet partial melting of the mantle. The mantle under the ocean has contact with water. When subduction, or continental plates pulling away from one another, occurs, the mantle will heat up and water is pushed into it.
Where is andesitic magma found?
Granitic, or rhyolitic, magmas and andesitic magmas are generated at convergent plate boundaries where the oceanic lithosphere (the outer layer of Earth composed of the crust and upper mantle) is subducted so that its edge is positioned below the edge of the continental plate or another oceanic plate.
What type of melting typically happens at mid-ocean ridges where two pieces of lithosphere are pulling apart making the lithosphere thinner?
This is called decompression melting. The basaltic magma thus formed, slowly migrates toward the surface and intrudes into fractures forming at the midocean ridge.
How is magma created in a subduction zone quizlet?
Magma is produced in subduction zones by melting of the oceanic crust of the subducting plate.
What hardens to form new rock at mid-ocean ridges?
Mid-ocean ridges are the boundaries between tectonic plates and are the place where the plates spread apart from each other. Magma from the underlying mantle erupts at the edges, then cools and solidifies to form new ocean crust.
What is mafic magma?
Describes magma that contains lower amounts of silica and is generally less viscous and less gas-rich than silicic magma. Tends to erupt effusively, as lava flows. Includes andesites (57-63 percent SiO2), basaltic andesites (53-57 percent SiO2), and basalts (47-53 percent SiO2).
Where is rhyolitic magma found?
Rhyolite has been found on islands far from land, but such oceanic occurrences are rare. The tholeiitic magmas erupted at volcanic ocean islands, such as Iceland, can sometimes differentiate all the way to rhyolite, and about 8% of the volcanic rock in Iceland is rhyolite.
What is rhyolitic magma?
Rhyolitic lavas are viscous and tend to form thick blocky lava flows or steep-sided piles of lava called lava domes. Rhyolite magmas tend to erupt explosively, commonly also producing abundant ash and pumice.
Why does magma form at subduction zones?
As a tectonic plate slides into the mantle, the hotter layer beneath Earth's crust, the heating releases fluids trapped in the plate. These fluids, such as seawater and carbon dioxide, rise into the upper plate and can partially melt the overlying crust, forming magma.
How is magma created in the subduction zone?
As the denser tectonic plate subducts, or sinks below, or the less-dense tectonic plate, hot rock from below can intrude into the cooler plate above. This process transfers heat and creates magma. Over millions of years, the magma in this subduction zone can create a series of active volcanoes known as a volcanic arc.
What is felsic magma?
Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are usually light in color and have specific gravities less than 3.
What is andesitic lava?
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende.
What type of magma is basaltic?
Basaltic lava is another term for mafic lava. Mafic lava is molten rock that is enriched in iron and magnesium and low in silica. When mafic lava cools on the earth's surface, it forms basalt, which is why mafic lava is commonly called 'basaltic lava.
What type of magma is produced at subduction zones?
As the plate sinks deeper, it can reach depths of 50 to 100 miles (80-160 kilometers) were it is so hot that the crust releases fluids trapped inside. The fluid melts some of the silica-rich minerals in the overlying material producing dark, silica-poor basaltic magma.