Question

arrange the metamorphic rocks in order from highest grade to lowest grade.

Explanation:

Define metamorphic grade

Metamorphic grade refers to the intensity of metamorphism that has affected a rock, which is primarily determined by the temperatures and pressures the rock experienced during its formation. Higher temperatures and higher pressures correspond directly to a higher metamorphic grade.

Analyze the data for each rock

We examine the temperature and pressure values given in the table for each rock:

• Rock 1: Temperature = \(300^\circ\text{C}\), Pressure = \(6\text{ kilobars}\)
• Rock 2: Temperature = \(1,000^\circ\text{C}\), Pressure = \(18\text{ kilobars}\)
• Rock 3: Temperature = \(600^\circ\text{C}\), Pressure = \(9\text{ kilobars}\)
• Rock 4: Temperature = \(100^\circ\text{C}\), Pressure = \(5\text{ kilobars}\)

Compare and rank the conditions

Comparing both temperature and pressure values across the four rocks, we can establish a clear, consistent order from the most extreme conditions (highest grade) to the mildest conditions (lowest grade):

1. Rock 2 has the highest temperature (\(1,000^\circ\text{C}\)) and highest pressure (\(18\text{ kilobars}\)).
2. Rock 3 has the second highest temperature (\(600^\circ\text{C}\)) and pressure (\(9\text{ kilobars}\)).
3. Rock 1 has the third highest temperature (\(300^\circ\text{C}\)) and pressure (\(6\text{ kilobars}\)).
4. Rock 4 has the lowest temperature (\(100^\circ\text{C}\)) and lowest pressure (\(5\text{ kilobars}\)).

Determine the final sequence

Ordering the metamorphic rocks from highest grade to lowest grade yields:

$$\text{Rock 2} ightarrow \text{Rock 3} ightarrow \text{Rock 1} ightarrow \text{Rock 4}$$

Answer:

The correct sequence of the metamorphic rocks from highest grade to lowest grade is:

1. Rock 2
2. Rock 3
3. Rock 1
4. Rock 4