Basaltic magma is high in iron, magnesium, and calcium but low in potassium and sodium. … Andesitic magma has moderate amounts of these minerals, with a temperature range from about 800oC to 1000oC (1472oF to 1832oF). Rhyolitic magma is high in potassium and sodium but low in iron, magnesium, and calcium.
How do basaltic rhyolitic and andesitic magmas differ quizlet?
BASALTIC magmas have a LOW SILICA content (45-55%) and referred to as MAFIC in composition. RHYOLITIC magma contains more than 65% SILICA and is referred to as FELSIC. ANDESITIC magma is INTERMEDIATE in composition (55-65% SILICA).
What is the difference between basaltic and rhyolitic magma?
Basaltic magma has a low viscosity whereas rhyolitic magma has a high viscosity. … One characteristic surface of a basalt flow is called pahoehoe which has a ropy or billowy surface. Basaltic eruptions are non-explosive.
What are the two features that differentiate basaltic magma from rhyolitic magma?
Basaltic Magma has a low silica content, causing it to have a low viscosity. Contrary, Rhyolitic Magma has a high silica content, causing it to have a high viscosity.
Why are the viscosities of basaltic and rhyolitic magma so different?
Summary Table | Magma Type | Rhyolitic |
---|---|---|
Solidified Rock | Rhyolite | |
Chemical Composition | 65-75 SiO2 %, low in Fe, Mg, Ca, high in K, Na. | |
Temperature | 650 – 800 oC | |
Viscosity | High |
What is the difference between basaltic magma and rhyolitic magma quizlet?
Basaltic Magma has a low silica content, causing it to have a low viscosity. Contrary, Rhyolitic Magma has a high silica content, causing it to have a high viscosity.
What are the physical differences between felsic rhyolitic and mafic basaltic lavas quizlet?
Rhyolitic (felsic) lava, with its high silica content (over 70 percent), is very viscous and forms short, thick flows. Basaltic (mafic) lava, with a lower silica content (about 50 percent), is more fluid and may travel a long distance (90 miles/150 km) before congealing.
What is basaltic magma?
Basaltic lava, or mafic lava, is molten rock enriched in iron and magnesium and depleted in silica. Basaltic magmas are formed by exceeding the melting point of the mantle either by adding heat, changing its composition, or decreasing its pressure.
Why do basaltic lavas have lower viscosity than rhyolitic lavas?
A basaltic lava flow has a low viscosity due to its low SiO2 content. Eruptions associated with basaltic lava usually are not explosive due to the low silica and gas content. Gases escape more easily when silica content is low. Because of the low viscosity, basaltic lava flows spread out, forming extensive layers.
What is andesitic magma?
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). … Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. Andesites erupt at temperatures between 900 and 1100 ° C.
What is the difference between andesitic magma and basaltic magma?
Basaltic magma is high in iron, magnesium, and calcium but low in potassium and sodium. It ranges in temperature from about 1000oC to 1200oC (1832oF to 2192oF). Andesitic magma has moderate amounts of these minerals, with a temperature range from about 800oC to 1000oC (1472oF to 1832oF).
Is basaltic magma fluid or viscous?
Viscosity of Magmas
Thus, basaltic magmas tend to be fairly fluid (low viscosity), but their viscosity is still 10,000 to 100,0000 times more viscous than water. Rhyolitic magmas tend to have even higher viscosity, ranging between 1 million and 100 million times more viscous than water.
Which characteristic of magma does not determine its explosiveness?
Viscosity, together with the amount of gas dissolved in magma, can determine the explosivity of the eruption. More viscous magma with volatiles is more explosive than less viscous magma, where gases can bubble out relatively easily.
Which one of the following magmas shows the highest magma viscosity?
The magma that has the highest viscosity is rhyolitic magma. One of the main reasons for the high viscosity in rhyolitic magma is that it contains a…
Which is more viscous basaltic or granitic magma?
i) In general > silica content, > viscosity of magma, believed to result from tendency of complex silica anions to form long chains of molecules before crystallization begins. Thus granitic magmas are more viscous than basaltic magmas.
Does cooler magma flow more or less quickly than hotter magma?
In general, cooler magma flows less quickly than hotter magma, which is the common thermodynamics for most objects on our planet.
Why is basaltic magma fluid and runny?
Basaltic magmas are derived from the partial melting of mantle rock. … Because the silica is diluted with other mineral components at a high temperature, the magma is very runny and thus not very viscous.
What is rhyolitic magma?
Rhyolite (/ˈraɪ. əlaɪt/ RY-ə-lyte) is the most silica-rich of volcanic rocks. … Magma with the composition of rhyolite is extremely viscous, due to its high silica content. This favors explosive eruptions over effusive eruptions, so rhyolitic magma is more often erupted as pyroclastic rock than as lava flows.
Why is higher silica magma or lava more viscous quizlet?
Higher silica increases viscosity. Magmas that have a high silica content will therefore exhibit greater degrees of polymerization, and have higher viscosities, than those with low-silica contents.
How do craters differ from Calderas quizlet?
What is the difference between a crater and a caldera? A crater is a funnel shaped pit at the top of a volcanic vent whereas a caldera is a basin shaped depression formed when the volcanic cone collapses due to magma chamber below getting empty of magma.
Which magma type andesitic or basaltic is associated with more violent eruptions?
Large composite volcanoes are made from andesitic magmas and are generally the result of much more violent eruptive events. Contrast the composition of a typical lava dome and a typical fissure eruption. A lava dome will tend to be felsic to intermediate while a fissure eruption will emit basaltic lava.
How do craters differ from Calderas?
Craters are formed by the outward explosion of rocks and other materials from a volcano. Calderas are formed by the inward collapse of a volcano. Craters are usually more circular than calderas.
What properties do granitic or rhyolitic magmas have?
The high gas content and high viscosity of these magmas are perfect for producing an explosive eruption. The viscosity can be so high that the gas can only escape by blasting the magma from the vent. Granitic magmas have produced some of the most explosive volcanic eruptions in Earth’s history.
What is the difference between Felsite and basalt lava?
Mafic lava creates basalt while felsic lava produces andesitic and rhyolite rocks. … Either in describing rocks or lava, mafic means that the lava or rock has less silica while felsic implies that the lava or rock has the most silica.
What process is thought to generate most granitic magmas and most basaltic magmas?
What is the process that is thought to generate most granitic magmas? A basaltic pond of magma becomes trapped below continental crust and partially melts this silica-rich crust into a granitic magma.
What are basaltic plateaus?
[pla′tō bə′sȯlt] (geology) One or a succession of high-temperature basaltic lava flows from fissure eruptions which accumulate to form a plateau. Also known as flood basalt.
Why do gases have a strong influence on eruptions of rhyolitic lavas but less so on basaltic eruptions?
Why do gases have a strong influence of eruptions of rhyolitic lavas, but less so on basaltic eruptions? Gases are trapped beneath the high viscosity rhyolitic lava.
Does basaltic magma have high silica content?
Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). Because of basalt’s low silica content, it has a low viscosity (resistance to flow). … Basaltic lavas are more fluid than andesites or dacites, which contain more silica.
How do andesitic magmas form?
Andesitic magma is formed through wet partial melting of the mantle. The mantle under the ocean has contact with water. … Basaltic magma with a high water content is the result. If this type of basaltic magma melts with continental crust that has a high density of dioxide silicon, andesitic magma will form.
What is magma How does magma differ from lava?
Scientists use the term magma for molten rock that is underground and lava for molten rock that breaks through the Earth’s surface.
Where are andesitic magmas generated?
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 the difference between andesitic and basaltic?
Both lavas are formed at different plate boundaries which is why they have different silica contents: the basaltic lava forms from the hot mantle material at constructive plate boundaries and hotspots whereas the andesitic lava forms at destructive plate boundaries from melting crust.
How can you tell the difference between andesite and basalt?
It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the feldspar in the rock consisting of plagioclase. This places andesite in the basalt/andesite field of the QAPF diagram. Andesite is further distinguished from basalt by its silica content of over 52%.
Is rhyolitic magma felsic?
Rhyolite is a felsic extrusive rock. Due to the high silica content, rhyolite lava is very viscous. … If rhyolite magma is gas rich it can erupt explosively, forming a frothy solidified magma called pumice (a very lightweight, light-coloured, vesicular form of rhyolite) along with ash deposits, and / or ignimbrite.
Which characteristics correctly describe magma?
Magmas are mainly liquid and contain dissolved fluids such as water; most are less dense than the adjacent solid rock.
Is basaltic lava thick or thin?
Although these lava flows are often more viscous, and typically thicker, than pahoehoe lavas they tend to advance at greater rates. Their flow fronts can vary from two meters to as much as twenty meters thick. Their forward motion is similar to the movement of a tractor tread.
How does the viscosity of magmas relate to the physical appearance of volcanoes?
Magmas with a higher SiO2 content have a higher viscosity. Ultimately, the viscosity of a magma will determine the shape a volcano takes over continued eruptions.
Which characterized of magma mainly determines its explosiveness?
The amount of dissolved gas in the magma provides the driving force for explosive eruptions. The viscosity of the magma, however, is also an important factor in determining whether an eruption will be explosive or nonexplosive.
What characteristic of magma mainly determines its explosiveness *?
It’s Silica content and therefore it’s viscosity. The higher content the higher the viscosity and generally the lower the temperature which it erupts at, also raising the viscosity. The higher the viscosity, the the greater the violence of the eruption.
What is the difference between basaltic magma and rhyolitic magma list at least three characteristics for each type of magma?
List at least three characteristics for each type of magma. Basaltic Magma has a low silica content, causing it to have a low viscosity. Contrary, Rhyolitic Magma has a high silica content, causing it to have a high viscosity. Basaltic Magma is very mild and quiet, while Rhyolitic Magma is catastrophic.
Why is rhyolitic magma highest viscosity?
Magma Composition:
Such magmas erupt as andesites and rhyolites or are intruded as granite masses. The more extensive silicate chain molecules render these magmas highly viscous, so when eruption occurs it is usually explosive (e.g. Mt St Helens).
Why does rhyolitic magma have the highest viscosity?
Summary Table | Magma Type | Rhyolitic |
---|---|---|
Solidified Rock | Rhyolite | |
Chemical Composition | 65-75 SiO2 %, low in Fe, Mg, Ca, high in K, Na. | |
Temperature | 650 – 800 oC | |
Viscosity | High |