As they rise, gas molecules in the magma come out of solution and form bubbles and as the bubbles rise they expand. Eventually the pressure from these bubbles is stronger than the surrounding solid rock and this surrounding rock fractures, allowing the magma to get to the surface.
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What controls the rise of magma?
The magma rises and collects in chambers within the crust. As magma fills the chamber, pressure grows. If the pressure gets high enough, the magma can break through the crust and spew out in a volcanic eruption. Most explosive volcanoes occur above subduction zones.
What controls viscosity in 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 is magma chemistry?
Like solid rock, magma is a mixture of minerals. It also contains small amounts of dissolved gases such as water vapor, carbon dioxide, and sulfur. The high temperatures and pressure under Earth’s crust keep magma in its fluid state.
What forces the magma beneath to move?
The compression of plates at these subduction zones forces the magma beneath them to move. Magma can not move through the newly compressed crust in as easily a manner. This means it tends to pool in magma chambers beneath the surface and between the converging tectonic plates.
What causes magma to rise to Earth’s surface?
Magma can rise when pieces of Earth’s crust called tectonic plates slowly move away from each other. The magma rises up to fill in the space. When this happens underwater volcanoes can form. Magma also rises when these tectonic plates move toward each other.
What factors affects the formation of 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.
Why does magma rise to the surface quizlet?
Magma rises because its less dense than surrounding rock.
What is the main factor that controls how explosive a volcanic eruption will be?
A volcano’s explosiveness depends on the composition of the magma (molten rock) and how readily gas can escape from it. As magma rises and pressure is released, gas bubbles (mainly of water vapor and carbon dioxide) form and expand rapidly, causing explosions.
What affects lava viscosity?
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).
How does viscosity affect magma?
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. A magma’s silica content will not only control the rock type that forms, it also controls the relative viscosity of the magma.
What two principal factors affect the viscosity of magma lava?
a. The viscosity of a magma is affected by its silica content and temperature. The amount of silica influences the magma’s viscosity in such a way that if the silica content is low, the magma would have low viscosity, whereas a high content of silica would make the magma more thick and sticky.
What are the physical and chemical properties of magma?
Several interrelated physical properties determine the characteristics of magma, including chemical composition, viscosity, dissolved gases, and temperature. Molten, or hot liquefied, rock located deep below Earth’s surface is called magma.
What happens when magma reaches the surface?
When magma reaches Earth’s surface and erupts from a volcano, it becomes lava.
How does magma chemistry influence eruption type?
Magma composition has a large effect on how a volcano erupts. Felsic lavas are more viscous and erupt explosively or do not erupt. Mafic lavas are less viscous and erupt effusively. Different lava types create different rock types, such as pahoehoe and a’a.
What is the process in which magma rises to the surface and becomes lava?
When magma rises from deep within the earth and explodes out of a volcano, it is called lava, and it cools quickly on the surface. Rock formed in this way is called extrusive igneous rock. It is extruded, or pushed, out of the earth’s interior and cools outside of or very near the earth’s surface.
Which pressure is responsible for volcanic eruption?
As gas bubbles accumulate, the upward pressure increases, forcing cracks in the rocks to widen, often in the direction of Earth’s surface. For magma to erupt from a volcano, this upward pressure must exceed the downward pressure that is exerted by the eight-kilometer (five mile) thick load of rock overhead.
How does pressure affect magma formation?
With increase in temperature the solid rock masses begin to vibrate first then bonding between them breaks and finally they convert into liquid we see as magma. This is the most important factor in the formation of magma.As we do down into the earth, the pressure is increased due to overlying rocks above.
Which factor affects the characteristic of magma and the rate at which it rises?
The speed of a magma flow depends on its viscosity – that is, its resistance to flow – which in turn depends upon how much water and silica are in the magma itself. Magmas with higher silica concentration are more viscous, and thus move slower than magmas with less silica.
What controls the speed of lava flow?
The speed at which lava moves across the ground depends on several factors, including (1) type of lava erupted and its viscosity; (2) steepness of the ground over which it travels; (3) whether the lava flows as a broad sheet, through a confined channel, or down a lava tube; and (4) rate of lava production at the vent.
What controls the speed of lava flow quizlet?
What controls the speed of flow? Viscosity or resistance to flow, affect magma or lava speed. Magma with low viscosity flow more easily. Viscosity depends on temperature, volatile content, and silica content.
Which characteristics of magma mainly determines 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.
What factors influence the melting temperatures and viscosity of magmas?
Viscosity of Magmas 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).
Which of the following increases the viscosity of magma?
The viscosity of magma increases with: high % silica and cooler temperatures.
How does the temperature of magma affect its viscosity?
Lower temperature magmas have higher viscosity than higher temperature magmas (viscosity decreases with increasing temperature of the magma).