Both the temperature and mineral content of magma affect how easily it flows. The viscosity (thickness) of the magma that erupts from a volcano affects the shape of the volcano. Volcanoes with steep slopes tend to form from very viscous magma, while flatter volcanoes form from magma that flows easily.
What affects magma composition?
Different minerals within a rocks melt at different temperatures and the amount of partial melting and the composition of the original rock determine the composition of the magma.
What does the composition of magma determine for a volcano?
The composition of magma determines its viscosity , which affects how a lava flows and what kind of volcano forms from the lava. There are as many types of volcanic eruptions as there are eruptions.
What is composition of magma?
Magmas can vary widely in composition, but in general they are made up of only eight elements; in order of importance: oxygen, silicon, aluminum, iron, calcium, sodium, magnesium, and potassium (Figure 3.2. 1).
Which magma composition causes the most violent volcanic eruption Why?
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. These solid particles become pyroclasts or volcanic ash.
How the composition of magma affects its viscosity?
Viscosity is the resistance to flow (opposite of fluidity). Viscosity depends on primarily on the composition of the magma, and temperature . Higher SiO 2 (silica) content magmas have higher viscosity than lower SiO 2 content magmas (viscosity increases with increasing SiO 2 concentration in the magma).
How does magma viscosity affect the type of volcanic eruption?
Viscosity combines with other factors to determine how explosive magma will be. For example, small crystals in the magma help gases escape. More crystals in the magma enable more gas bubbles to form, and so they make an eruption more explosive. The rate at which pressure is reduced also affects the explosiveness.
What is magma How does magma differ from lava?
Magma is composed of molten rock and is stored in the Earth’s crust. Lava is magma that reaches the surface of our planet through a volcano vent.
Which location is a source of magma?
Magma is produced by melting of the mantle or the crust in various tectonic settings, which on Earth include subduction zones, continental rift zones, mid-ocean ridges and hotspots.
What happens to magma after it is formed?
Magma cools and crystallizes to form igneous rock . Igneous rock undergoes weathering (or breakdown) to form sediment. ... As the sedimentary rock is buried under more and more sediment, the heat and pressure of burial cause metamorphism to occur. This transforms the sedimentary rock into a metamorphic rock.
How does magma viscosity influence the explosive potential?
A more viscous (thick) magma will produce a more violent eruption This is controlled in part by the concentration of silica in the magma . A magma with low silica (<45%) will be runny and so the eruption will not be explosive. ... A magma with low silica (<45%) will be runny and so the eruption will not be explosive.
Which of the following characteristics of magma mainly affect the explosiveness of volcanic eruption?
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.
Can the same volcano produce volcanic rocks with different compositions?
Volcanoes produce different types of volcanic rocks . The creation of volcanic rocks depends on the type of eruption and the source and composition of the magma erupted. ... For example, basalt (a dark gray to black rock) contains more minerals of olivine and hornblende than andesite (a gray rock).
What are two important factors that affect the explosiveness of a volcanic eruption?
The two main factors that influence how a volcano will erupt are viscosity and gas content . Both are related to the composition of the magma.
How does composition of magma and temperature affect the viscosity of magma?
Explanation: Viscosity of magma, the resistance to flow depends on composition of the magma and temperature. Higher silica content means higher viscosity . ... Hence, lower viscosity and low gas content mean higher temperature of magma.
How does lava change its composition?
As the magma rises crystals begin to form. ... By settling the crystals are being removed from the magma , causing the chemical composition of system to change. As more and more olivine crystals settle, the magma has less and less magnesium oxide and more and more silica.
What affects the viscosity of magma and how do they affect it?
Magmas that have a high silica content will therefore exhibit greater degrees of polymerization, and have higher viscosities, than those with low-silica contents. The amount of dissolved gases in the magma can also affect it’s viscosity, but in a more ambiguous way than temperature and silica content.
What is the difference between magma and lava quizlet?
Magma and lava both refer to molten rock from which igneous rocks form . However, magma refers to molten rock below Earth’s surface, and lava refers to molten rock at the surface.
How does the viscosity of the magma fed to volcanoes affect nearby life and property?
How does the viscosity of the magma fed to volcanoes affect nearby life and property? A volcano that expels highly viscous magma is a greater threat to life and property because it is more explosive, and thus, is more difficult or impossible to predict. ... The viscosity and gas content of a magma determines how it erupts .
How is magma turned into lava?
Magma is extremely hot liquid and semi-liquid rock located under Earth’s surface. ... This magma can push through holes or cracks in the crust , causing a volcanic eruption. When magma flows or erupts onto Earth’s surface, it is called lava.
What is magma how does it differ from lava quizlet?
Magma is molten rock below the Earth’s surface, lava is molten rock that has erupted onto the surface.
Why is magma at divergent plate boundaries mafic in composition?
At divergent boundaries magma forms because of decompression melting . ... The initial magmas in most volcanic regions are mafic in composition, but they can evolve into more felsic types through interaction with crustal rock, and as a result of crystal settling within a magma chamber.
The composition of magma depends on the rock it was formed from (by melting) , and the conditions of that melting. ... All magmas have varying proportions of elements such as hydrogen, carbon, and sulphur, which are converted into gases like water vapour, carbon dioxide, and hydrogen sulphide as the magma cools.
Do you think magma rises or stay in place?
Once magma forms, it tries to rise . Buoyancy is the prime mover of magma because melted rock is always less dense than solid rock. Rising magma tends to remain fluid, even if it’s cooling because it continues to decompress.
What causes the magma to rise to the surface?
Magma can rise when pieces of Earth’s crust called tectonic plates slowly move away from each other . ... Magma also rises when these tectonic plates move toward each other. When this happens, part of Earth’s crust can be forced deep into its interior. The high heat and pressure cause the crust to melt and rise as magma.
Is magma a lava?
Scientists use the term magma for molten rock that is underground and lava for molten rock that breaks through the Earth’s surface.
What happens after the gases in the magma build up pressure?
As a result of its higher viscosity and gas content, intermediate magma builds up pressure below the Earth’s surface before it can be released as lava. This more gaseous and sticky lava tends to explode violently and cools as andesite rock. ... These trapped bubbles can cause explosive and destructive eruptions.
How does the silica content of magma affect how explosive a volcano can be?
The silica content of the magma determines how thick the magma is , how easily it flows and how easily dissolved gases within the magma can escape; therefore the silica content determines the characteristic of the volcanic eruption and the shape and size of the resulting volcanic cone.
What factors affect the violence of a volcanic eruption?
Although there are several factors triggering a volcanic eruption, three predominate: the buoyancy of the magma , the pressure from the exsolved gases in the magma and the injection of a new batch of magma into an already filled magma chamber.
Where are the volcanic rocks formed?
Extrusive, or volcanic, igneous rock is produced when magma exits and cools above (or very near) the Earth’s surface . These are the rocks that form at erupting volcanoes and oozing fissures.
How does magma temperature affect viscosity?
Viscosity is anti-correlated to temperature by the fact that a lower temperature means a higher viscosity. In other words, as magma cools, its viscosity increases . ... A higher concentration in silica leads to a more acid/more viscous magma.
– Viscosity depends upon temperature & magma composition (most important). -Magma composition varies with plate tectonic setting. -Pressure on magma decreases as magma rises toward surface. You just studied 24 terms!
Which characteristic of 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.
Which of the characteristics of a volcano depends on its magma emission?
The emission of volcanic gases depends on the thermodynamic conditions (pressure, temperature) and on the magma type (i.e., its chemical composition, which in turn depends on the tectonic environment). ... In general, this magma type is characterized by low viscosity and low gas content , and eruptions are mostly effusive.
How does the eruption of volcano lower the atmospheric temperature?
The gases and dust particles thrown into the atmosphere during volcanic eruptions have influences on climate. Most of the particles spewed from volcanoes cool the planet by shading incoming solar radiation . The cooling effect can last for months to years depending on the characteristics of the eruption.
What is one factor that determines how explosive a volcanic eruption quizlet?
The amount of water vapor and other gases present is one factor that determines whether a volcanic eruption will be quiet or explosive.
Why is the amount of gas in magma important in relation to volcanic eruptions?
Gases in Magmas
Gas gives magmas their explosive character, because volume of gas expands as pressure is reduced . The composition of the gases in magma are: Mostly H 2 O (water vapor) & some CO 2 (carbon dioxide)
