Final answer:
The increasing age of islands as you travel northwest in the Hawaiian chain demonstrates the movement of the Pacific Plate over a hot spot, providing key evidence for plate tectonics.
Step-by-step explanation:
The significance of the ages of the Hawaiian Islands in terms of plate tectonics is profound. The Hawaiian Islands are located over a 'hot spot' under the crust of the Pacific Plate. As this plate moves slowly over the hot spot, it leads to the formation of new islands. There is a pattern of the islands becoming older the farther northwest you travel. This progression in age provides evidence for the theory of plate tectonics and the movement of Earth's crust.
Learn more about Plate tectonics