Act Science

Explanation
Kyanite would most typically be found only in rocks of a medium grade.

Explanation
Based on Figure 1, it can be inferred that a Facies G rock will most likely form under the pressure and temperature conditions of 11 kb and 600°C. The other pressure and temperature combinations in the list do not correspond to Facies G based on the information provided in Figure 1.

Explanation
As depth increases, the pressure also increases. This is because the weight of the water above exerts more force on the water at deeper levels. The pressure increases due to the increased weight of the water column. There is no indication in Figure 1 that the pressure decreases at any point, so the correct answer is that the pressure increases only.

Explanation
Plagioclase is least helpful in determining a metamorphic rock's grade because it is a common mineral found in both low-grade and high-grade metamorphic rocks. Its presence alone does not provide specific information about the intensity of metamorphism or the degree of recrystallization that has occurred. In contrast, minerals like chlorite, muscovite, and staurolite are more indicative of specific metamorphic conditions and can help determine the grade of the rock.

Explanation
Based on the information given, hornfels is formed when magma heats sedimentary rocks. Facies A in Figure 1 represents the metamorphic facies that is associated with contact metamorphism, which occurs when magma intrudes into the surrounding rocks. Therefore, hornfels is most likely a member of Facies A.