Part 3: Porphyry 8. The igneous rock to the right has large, black-and- white co
ID: 286854 • Letter: P
Question
Part 3: Porphyry 8. The igneous rock to the right has large, black-and- white colored minerals and many small, gray minerals. You can tell it is an igneous rock because the minerals are rectangular and not rounded like sediments. How might the igneous rock shown to the right have formed? Porphyry 9. Two students are debating about the cooling rate of this rock, and the formation of the large minerals. Student 1: The magma must have gotten large pieces of sediments that we can see trapped in it, and the sediments didn't melt, even though they were in the magma. So, this rock formed because large pieces of sediment got picked up by lava, and then that lava cooled quickly. Student 2: This is an igneous rock, so everything started off as magma. The large minerals must have formed deep underground when the magma was cooling slowly, like in a magma chamber. But the rest of the rock has very small minerals, so they cooled quickly at the surface. With which of these students do you agree? Why? 10. Student 2 said that the large minerals formed deep underground, like in a magma chamber, and the small minerals formed at the surface. Describe what actually happened to form the rock. In other words, what story does the appearance of this rock tell us about its history? (Hint: In what situation is magma in a magma chamber moved to the surface?)Explanation / Answer
8. The rock shown in the image is formed in two different stages. Initially wen the magma was deep in the crust that time the slow cooling caused the crystaline structure which have bigger grain size almost greater than 2 mm and then the magma cooled rapidly at shallow depth so the grains structure formed is invisible to see with naked eyes.
9. Student 2 is correct as the ingenious rocks are formed by magma only, the bigger crystals are formed at the deeper portion where slow cooling is provided and the smaller crystaline structure is formed at shallow depth or when the magma erupts out of volcano.
Please ask rest of the questions in separate questionnaire.