Which of the following factors influence the composition of a magma?
The composition of magma depends on the rock it was formed from (by melting), and the conditions of that melting. Magmas derived from the mantle have higher levels of iron, magnesium, and calcium, but they are still likely to be dominated by oxygen and silicon.
Which of the following igneous rocks has a texture consistent with a magma that cooled and solidified slowly at first followed by more rapid cooling?
When magma cools slowly at first, but then cools more rapidly as it nears Earth's surface, the igneous rock that forms may have large crystals embedded within a mass of smaller crystals. This texture is called porphyritic texture.
What is the main cause of melting along subduction zones?
In a subduction zone (like the Cascades or the Andes), where an oceanic plate slides down under another plate, that downgoing slab releases its water as it heats up. That water then rises up into the mantle above it, causing it to melt at a lower temperature and, bam!
Which of the following can occur within a magma chamber?
Which of the following can occur within a magma chamber? Sinking or floating crystals may change the composition of the remaining magma. Wall rocks can melt and become incorporated into the magma. If two magmas mix, the resulting magma would be between the composition of the two magmas.
Which affects the viscosity of magma?
A magma's viscosity is largely controlled by its temperature, composition, and gas content (see downloadable programs at the bottom of this page). The effect of temperature on viscosity is intuitive. Like most liquids, the higher the temperature, the more fluid a substance becomes, thus lowering its viscosity.
Which of the following does not affect viscosity of magma?
Temperature Silica Content Amount of gas None of these affects the viscosity of the magma.
Which of the following makes the cooling rate of the magma slower?
Magma intruded deep in the crust where it is surrounded by warm wall rock, cools much slower than magma does intruded into cold wall rock near the ground surface. So closer to the surface wall rock = faster cooled magma. And wall rock in the deep crust = slower cooled magma.
What is the texture of an igneous rock formed from magma that cooled slowly underground?
PHANERITIC TEXTURE – Igneous rocks with large, visible crystals because the rock formed slowly in an underground magma chamber.
Which of the following are ways that viscosity affects gases in magma?
Which of the following are ways that viscosity affects gases in magma? Viscous magma prevents gas from escaping easily.
How does subduction trigger melting?
In a subduction zone (like the Cascades or the Andes) where an oceanic plate slides down under another plate that downgoing slab releases its water as it heats up. That water then rises up into the mantle above it causing it to melt at a lower temperature and bam!
What causes magma?
When an oceanic plate collides with a continental plate, it sinks into the mantle below. As the oceanic plate sinks, fluid (shown in purple) is squeezed out of it. The fluid flows up into the mantle rock above and changes its chemistry, causing it to melt. This forms magma (molten rock).
What happens to the gases within a magma that rises to shallower levels in the crust?
As magma rises to shallower levels, decreasing pressure allows the gases to form bubbles in the magma. If this occurs, the density of the magma decreases and the magma rises faster. If magma initially has a low content of dissolved gases, bubbles may not form or assist the magma upward.
What makes magma viscous?
Viscosity is the resistance to flow (opposite of fluidity). Viscosity depends on primarily on the composition of the magma, and temperature. Higher SiO2 (silica) content magmas have higher viscosity than lower SiO2 content magmas (viscosity increases with increasing SiO2 concentration in the magma).
What does it means by lower viscosity magma?
Low viscosity magmas allow gases to escape easily whereas gas pressures can build up in high viscosity magmas – resulting in violent eruptions. (Blowing through a straw, it's easier to get water to bubble than a milk shake)
What factors affect the viscosity of magma?
Temperature, composition, and volatile (gas) content largely determine the viscosity of lava. Temperature: The hotter the lava, the lower the viscosity (the thinner it is). The cooler the lava, the higher the viscosity (the thicker it is).
Which of the following affects the viscosity of a magma?
A magma's viscosity is largely controlled by its temperature, composition, and gas content (see downloadable programs at the bottom of this page). The effect of temperature on viscosity is intuitive. Like most liquids, the higher the temperature, the more fluid a substance becomes, thus lowering its viscosity.
What affects the viscosity of a magma which is more viscous hotter or cooler melts mafic or silicic felsic melts wet or dry melts?
Viscosity is dependent on the temperature, volatile content, and silica content of the magma or lava. Hotter magma is less viscous than cooler magma because the thermal energy breaks bonds and allows for the atoms to move more easily.
What is the texture of an igneous rock formed from magma that cooled slowly deep underground quizlet?
Igneous rock that formed from magma that hardened beneath Earth's surface. Slowly cooling magma forms coarse-grained rocks, such as granite, with large crystals.
Which eruption has lower viscosity magma?
Pahoehoe Flows – Basaltic lava flows with low viscosity start to cool when exposed to the low temperature of the atmosphere.
What causes subduction?
Subduction occurs when two plates collide at a convergent boundary, and one plate is driven beneath the other, back into the Earth's interior. Not all convergence leads to subduction. Continental rocks are too buoyant to be forced downward, so when continents collide, they crumple but stay at the surface.
What causes magma to form at a divergent plate boundary?
At divergent boundaries magma forms because of decompression melting. Decompression melting also takes place within a mantle plume.
How does the viscosity of magma change as magma cools?
How does the viscosity of magma change as magma cools? The viscosity increases when temperature decreases.
Which type of lava has the lowest viscosity?
Basaltic magma has the lowest viscosity, so more of it reaches the surface; the more viscous rhyolitic magmas are so sluggish that they tend to be trapped deep below the surface where they cool, solidify, and grow into the larger mineral crystals of plutonic rocks.
How does silica affect viscosity?
A magma's silica content will not only control the rock type that forms, it also controls the relative viscosity of the magma. Differences in a magma's viscosity will determine the shape a volcano takes. High-silica (basalt) magma has a much lower viscosity. It flows much easier and over longer distances.
What decreases the viscosity of magma?
A magma's viscosity is largely controlled by its temperature, composition, and gas content (see downloadable programs at the bottom of this page). The effect of temperature on viscosity is intuitive. Like most liquids, the higher the temperature, the more fluid a substance becomes, thus lowering its viscosity.
How does gas affect the viscosity of magma?
Viscosity of magma, the resistance to flow depends on composition of the magma and temperature. Higher silica content means higher viscosity. But lower temperatures and low gas content mean higher viscosity. Hence, lower viscosity and low gas content mean higher temperature of magma.
What makes mafic magma less viscous than felsic magma?
Felsic magma has more silica and alumina content, which makes magma more viscous. Mafic magma has less silica content and more iron and magnesium in it.
What is the texture of an igneous rock formed from magma that cools slowly deep underground Regents?
Igneous rock that formed from magma that hardened beneath Earth's surface. Slowly cooling magma forms coarse-grained rocks, such as granite, with large crystals. Intrusive Rocks have larger grains than extrusive rocks. Rapidly cooling lava forms fine-grained rocks with small crystals or no crystals at all.
What affects the viscosity of magma?
A magma's viscosity is largely controlled by its temperature, composition, and gas content (see downloadable programs at the bottom of this page). The effect of temperature on viscosity is intuitive. Like most liquids, the higher the temperature, the more fluid a substance becomes, thus lowering its viscosity.
How subduction cause the formation of the land mass like mountains and volcano?
Subduction zones always have mountain ranges caused by plate subduction. The next is volcanic activity as a plate is subducted the pressure and heat turns it into magma. These pockets of magma find paths to the surface and create volcanoes.