Final answer:
The Hawaiian Islands were formed by volcanic eruptions, but the Mississippi Delta was not.
Step-by-step explanation:
The Hawaiian Islands and the Mississippi Delta were formed through different geological processes. The Hawaiian Islands were formed from volcanic eruptions due to hotspot activity. The formation of the Mississippi Delta, on the other hand, is primarily attributed to the continental drift and the deposition of sediments carried by the Mississippi River.
Therefore, the correct comparison is that the Hawaiian Islands were formed by volcanic eruptions, but the Mississippi Delta was not.