What magma is the most abundant?
Oxygen, the most abundant element in magma, comprises a little less than half the total, followed by silicon at just over one-quarter. The remaining elements make up the other one-quarter.
What types of volcanoes are formed at spreading centers?
Shield volcanoes Shield volcanoes are common at spreading centers or intraplate hot spots. The lava that creates shield volcanoes is fluid and flows easily and creates the shield shape. Shield volcanoes are built by many layers over time and the layers are usually of very similar composition.
How is magma formed in spreading center?
Along mid-ocean ridges (also called spreading centers), tectonic plates are moving apart. Molten rock rises from Earth's mantle into the gap between the separating plates and produces extensive lava flows. Along oceanic trenches, tectonic plates are colliding so that one plate is descending below another plate.
How is magma generated at spreading centers quizlet?
Mantle rock rises and fills gaps between plates. As rock rises decompression melting occurs (less pressure/lower temp to melt). Magma forms and erupts along axis of the spreading center.
Which type of magma is the most abundant type of magma erupted on Earth?
geo quiz 6
| Question | Answer |
|---|---|
| ________ is a major dissolved volatile constituent in both magmas and volcanic gases. | Water |
| Volcanic bombs originate ________. | as erupted magma blobs that partly congeal before falling to the ground |
| ________ magma is the most abundant type erupted at oceanic spreading centers. | Basaltic |
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.
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 made at a spreading center?
Spreading centers occur where two plates are moving away from each other, and deep cracks are opened through the crust. This lengthening of the crust allows magma from the upper mantle to rise to the surface and cool, commonly forming basalt. An excellent example is the Mid-Atlantic Ridge.
What is oceanic spreading center?
The oceanic spreading center, also known as the midocean ridge, is an underwater mountainous feature lying between the two lithospheric plates, through which new magma material being continuously spread out and lead to growth of the lithospheric plates.
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.
How is magma formed at mid-ocean ridges?
Mid-Ocean Ridge Volcanism 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.
What is the most abundant volatile in magma?
water The most abundant volatile in magma is water (H2O), followed typically by carbon dioxide (CO2), and then by sulphur dioxide (SO2). The general relationship between the SiO2 content of magma and the amount of volatiles is shown in Figure 4.8.
Which type of magma would you expect to produce the most explosive volcanic eruption?
Explosive eruptions are favored by high gas content & high viscosity magmas (andesitic to rhyolitic magmas). The explosive bursting of bubbles fragments the magma into clots of liquid that cool as they fall through the air.
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 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).
What type of melting occurs at mid-ocean ridges?
Decompression melting Decompression melting occurs at mid-ocean ridges. When two plates move apart, they create a space that can be filled by hot rock that rises buoyantly from below.
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.
What type of magma is at a mid-ocean ridge?
basalt Mid-Ocean Ridge Magmatism: By far, the dominant type of lava resulting from magmatic activity at mid-ocean ridges is basalt, also called mid-ocean ridge basalt (MORB). However, small amounts of other extrusive magma types (predominantly andesite, dacite, and picrite) also erupt there.
What is the source of magma that forms at oceanic ridges?
upwelling mantle Mid-Ocean Ridge Volcanism 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 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.
Which type of volcano the magma content is high?
Viscosity of Magmas
| Summary Table | ||
|---|---|---|
| Magma Type | Solidified Rock | Gas Content |
| Basaltic | Basalt | Low |
| Andesitic | Andesite | Intermediate |
| Rhyolitic | Rhyolite | High |
Sep 14, 2015
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 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 type of lava is most common at mid-ocean ridges?
basaltic lavas At mid-ocean ridges, eruptions are generally dominated by the gentle effusion of basaltic lavas with a low volatile content.
How is magma formed in mid-ocean ridge?
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.
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 generated at spreading 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.
How does magma form at a mid-ocean spreading ridge?
Mid-Ocean Ridge Volcanism 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.
How is magma formed in oceanic crust?
Magmas generated by melting of the Earth's mantle rise up below the oceanic crust and erupt on the Earth's surface at mid-ocean ridge systems, the longest mountain ranges in the world. When the magma cools it forms basalt, the planet's most-common rock and the basis for oceanic crust.
What type of magma is created at mid-ocean ridge 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).