How does grain size reflect the cooling time of magma?
If magma cools quickly, for example when basalt lava erupts from a volcano, then many crystals form very quickly, and the resulting rock is fine-grained, with crystals usually less than 1mm in size. If magma is trapped underground in an igneous intrusion, it cools slowly because it is insulated by the surrounding rock.
How does grain size reflect the cooling rate of a magma did the pictured rock come from rapidly or slowly cooling magma?
How does grain size reflect the cooling time of a magma? Extrusive rocks cool rapidly and have small grains. Intrusive rocks cool much slower and have more time to grow larger grains.
What affects the formation of magma?
Differences in temperature, pressure, and structural formations in the mantle and crust cause magma to form in different ways. Decompression MeltingDecompression melting involves the upward movement of Earth's mostly-solid mantle. This hot material rises to an area of lower pressure through the process of convection.
Why are there so many different types of magma quizlet?
Why are there so many different types of magmas? Because it depends on the source, how it interacts with its surroundings (assimilation), and whether crystals sink as they form (partial melting and magma mixing).
What does the mixture of grain sizes in a porphyritic igneous rock indicates about its cooling history?
What does the mixture of grain size in a porphyritic igneous rock indicate about its cooling history? This indicates that some cooled slowly at depth, so that large phenocrysts form, then the melt erupted and the remainder cools quickly.
How is the size of the mineral grains affected by the rate at which molten rock material cools?
If the magma cools slowly then the reactions proceed for a longer period of time and the resulting mineral crystals (grains) become large. If the magma cools rapidly then the reactions are much quicker and the mineral crystals (grains) are smaller.
How does the rate of cooling affect the size of crystals in an igneous rock?
If the magma cools quickly, the crystals do not have much time to form, so they are very small. If the magma cools slowly, then the crystals have enough time to grow and become large.
What effect does a fast cooling rate have on grain size in igneous rocks?
The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals.
What happens to the viscosity of magma as it cools?
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. This property is increased by crystallization of magma while temperature decreases.
What does a mixture of grain sizes in a porphyritic igneous rock tell us about its cooling history quizlet?
A porphyritic rock can have a fine or coarse-grained groundmass. Porphyritic texture indicates two-stage cooling: slow, then fast.
How does the grain size of intrusive igneous rocks differ from that of extrusive igneous rocks Why?
Because extrusive rocks cool quickly, they only have time to form very small crystals such as basalt or none at all. On the other hand, intrusive rocks grow larger crystals because they take longer to cool. Extrusive rocks are usually fine-grained or glassy while intrusive rocks are coarse-grained.
What does the grain size of an igneous rock tell you about the cooling rate during its formation?
The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals.
How does mineral size relate to cooling rate?
Texture — the size of the crystals can be crudely related to the rate of cooling. The higher the rate of cooling the smaller the size of the crystals. The rate of cooling is proportional to the difference in temperature between the bodies in contact with heat flowing from the warmer body to the cooler body.
What is the relationship between cooling rate and the size of minerals?
When magma cools, crystals form because the solution is super-saturated with respect to some minerals. If the magma cools quickly, the crystals do not have much time to form, so they are very small. If the magma cools slowly, then the crystals have enough time to grow and become large.
What will increase the viscosity of the magma?
Viscosity of Magmas 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 is viscosity of magma decreases with?
temperature Lower temperature magmas have higher viscosity than higher temperature magmas (viscosity decreases with increasing temperature of the magma).
What does porphyritic texture tell you about the cooling history of an igneous rock?
What does a porphyritic texture indicate about the cooling history of an igneous rock? It indicates that crystals were formed at depth (slow cooling) and then the magma moved to a shallow depth or erupted (fast cooling). The classification of igneous rocks is based largely on two criteria.
What would you infer about the rate of cooling of an igneous rock that has a porphyritic texture?
Porphyritic:a mixture of large and small crystals – perhaps a two-stage cooling history with the large crystals (the phenocrysts) cooling slowly and the small crystals (the groundmass) cooling more quickly.
How does the rate of cooling affect the size of mineral crystal?
How does cooling rate affect the crystal size of minerals in igneous rocks? –Slow cooling produces larger crystals; quick cooling produces smaller crystals.
Why does a higher temperature cause the viscosity of a magma to decrease?
As temperature increases, viscosity decreases because the flow rate gets faster. The liquid does not resist movement when hot. VISCOSITY is directly related to the amount of silica (sand) in the magma. As silica content increases, viscosity increases.
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.
What does a mixture of grain sizes in a porphyritic igneous rock tell us about its cooling history?
What does the mixture of grain size in a porphyritic igneous rock indicate about its cooling history? This indicates that some cooled slowly at depth, so that large phenocrysts form, then the melt erupted and the remainder cools quickly.
How do you determine the cooling rate of igneous rocks?
It is also determined by the rate that the magma cools. If the magma cools deep underground, it cools slowly. If the magma cools at or very near the surface, it cools quickly.
What does the texture of igneous rocks tell us about cooling history?
The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals.
How does cooling rate affect?
As the rate of cooling increases, crystal size decreases. This means that something which cools very quickly will have smaller crystal formations, and something which cools slowly will have larger crystal formations. This is easily seen in igneous rock, which may cool at variable rates.
What are the factors affecting 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 would decrease the viscosity of magma?
Which of the following would decrease the viscosity of magma? The more the silica in magma, the lower the viscosity.
What does a porphyritic texture indicate about the cooling history of an igneous rock quizlet?
What does a porphyritic texture indicate about the cooling history of an igneous rock? It indicates that crystals were formed at depth (slow cooling) and then the magma moved to a shallow depth or erupted (fast cooling).
What does the texture of this rock indicate about its cooling history the magma cooled?
The texture of an igneous rock is determined by the cooling history of the magma from which it formed. … Phaneritic texture describes coarse grained rocks. They are characteristic of intrusive (plutonic) rocks and have crystals that can be seen with the unaided eye. Indicates slow cooling history.
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.