In the lab, you learned how cooling rate affects the texture of igneous rocks. D
ID: 801738 • Letter: I
Question
In the lab, you learned how cooling rate affects the texture of igneous rocks. Describe a situation in which a porphyritic texture might develop in an igneous rock. Rivers and stream systems tend to originate in mountainous areas, where they erode into the surrounding rock and transport large volumes of sediment. The velocity of water in rivers Is influenced by a variety of factors, one of which Is the volume of water being transported. The volume of water In a stream fluctuates depending upon the amount of precipitation, melt, and runoff it receives. Therefore, a stream's velocity (and, thus, capacity to carry large sediments) varies over time. Based on this information, along with your observations from lab, which sedimentary rock in your kit was likely formed in a fluvial (river or stream) environment ?Explanation / Answer
3) porphyritic texture is an inequigranular texture in which large grains are surrounded in a fine grained matrix. porphyritic texture can be developed in several ways.
porphyritic texture form when same magma has cooled/crystallized in two different environments, such as plutonic and volcanic. porphyry crystals or large crystals are developed during the cooling of magma in plutonic conditions and fine grain crystals are formed in volcanic conditions when the magma has erupted after cooling to some extent in plutonic conditions.
porphyric texture can also be formed when a magma is rich in one componet/mineral than the remaining . the mineral which is rich in magma will form larger grains and the remaining portion will be left as fine grained ground mass
4) there are several rocks which can be formed by the action of river, they are sandstone, conglomerate, shale etc
if stream velocity is high then we can find conglomerates , if velocity is low to medium we can find sandstone and if the velocity is too low then shales are formed
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