Step 1: Sort the four places by tectonic type.
We need to tie each location to the kind of plate feature it shows. Each spot is famous for one clear setting.
Step 2: Iceland.
Iceland lies on the Mid Atlantic Ridge and also sits over a plume, so it is a plume meeting a spreading ridge. This points to feature (ii).
Step 3: Afar.
Afar is where three rift arms meet, a triple junction. So Afar takes feature (i).
Step 4: Hawaii.
Hawaii is a hotspot chain made as the Pacific plate slides over a fixed plume. That gives feature (iv).
Step 5: Aleutians and final match.
The Aleutian Islands form a subduction arc where the Pacific plate dives down, so they take feature (iii). Putting it together gives P-ii, Q-i, R-iv, S-iii.
\[ \boxed{\text{P-ii; Q-i; R-iv; S-iii}} \]
