0
Porphyritic texture indicates that a magma has gone through a two stage cooling process. The magma has cooled sufficiently underground to allow some minerals to crystallize and grow in size; the magma is then expelled above ground where the remaining liquid magma solidifies quickly, allowing only small crystals to develop.
Wiki User
∙ 13y ago
Wiki User
∙ 13y agoA porphyritic texture occurs when the magma already contains large crystals migrates to a new location where the rate of cooling increases.
Wiki User
∙ 13y agoMainly the time spent by magma or lava in the cooling process.
Wiki User
∙ 10y agoLonger time spent cooling=increased crystal size.
Add your answer:
Earn +20 pts
What determines the mineral grain size in an igneous rock?
The cooling rate of the rock.
What does phaneritic mean?
Phaneritic refers to igneous rock grain size,which is visible with the naked eye.
What is the grain size of a fine grained igneous rock?
The individual grains (crystals) in quickly cooled magma are described as aphanitic--not visible without magnification.
What size is an intrusive Igneous Rock?
It can be any size. The only specific factor of the intrusive rock is that is took a very long time to cool.
What do small crystals in an igneous rock mean?
The size of the crystals in an igneous rock tells us how fast the magma cooled.
What determines the mineral grain size in an igneous rock?
The cooling rate of the rock.
What controls the grain size of igneous rock?
The rate at which the igneous rock cools controls grain size. Slower cooling results in larger crystals while faster cooling results in smaller crystals.
What is a factor that controls grain size in igneous rock?
It depends on if it is intrusive or extrusive. If it is an intrusive rock, it is formed when magma hardens under the earth and has a larger grain size. If it is an extrusive rock, it is formed when lava hardens on the earth's surface and has a smaller grain size.
What is the grain size of an extrusive igneous?
It depend what rock it is but extrusive rocks generally non-crystalline or have a grain size of less than 1 mm
What does phaneritic mean?
Phaneritic refers to igneous rock grain size,which is visible with the naked eye.
Does grain size mean anything when identifying igneous rocks?
yes, it does. when a grain size in an igneous rock is small, it means that it was probably an extrusive rock, meaning it formed on land. but if the grain size is big, it means that the rock most likely formed underground, or it was intrusive. try remembering it like this- the larger the crystals, the more time the rock had to form, and magma cools faster on land, not giving the rocks much time to form.
How can you determine if a igneous rock has had an intrusive or extrusive origin?
== Grain size. Most intrusive igneous rocks will have visible crystals. Crystals in most extrusive igneous rocks are not easily visible.
What size of rock texture refers to igneous rock?
The size of the mineral crystals in an igneous rock determines the rock's texture.
Is conglomerate intrusive or extrusive?
Neither. Conglomerate is a sedimentary rock. Intrusive and extrusive are descriptive terms used to classify igneous rocks.
What is the grain size of a fine grained igneous rock?
The individual grains (crystals) in quickly cooled magma are described as aphanitic--not visible without magnification.
What determines the grain shape of a rock?
The size and shape of grain in igneous rock is determined by the same factors. Everything depends on how fast or slow the molten rock cools. If the molten rock is extruded from a volcano, it cools so fast that a very fine grained rock is the result.
What does grain size tell you about the orgin and cooling time of an igneous rock?
The larger the crystals, the more time it had to cool because the crystals had more time to grow
