Final answer:
All three, Surtsey Island, Mt. St. Helens, and Yellowstone, are active volcanic areas, with Yellowstone showing more volcanism compared to Anaheim due to its significant calderas and history of larger eruptions.
Step-by-step explanation:
The similarity between Surtsey Island, Mt. St. Helens, and Yellowstone is that a. All three are active volcanic areas. These locations are known for their volcanic activity due to the presence of hotspots or plate boundaries. The Yellowstone hotspot is particularly noteworthy, currently residing under Yellowstone National Park, and has created a series of calderas. By contrast, the Anaheim hotspot in Canada is less active in terms of volcanism when compared to Yellowstone over the same period. Regarding whether the rate of motion of the North American plate has been constant along the hotspot track, geological studies suggest variations over time. As the plate moves over hotspots like Yellowstone and Anahim, eruptions occur creating calderas, with Yellowstone's being larger. The size of calderas can relate to the amount of volcanic material present, and Yellowstone's history of large eruptions, such as the Gray's Landing event 8.72 million years ago, suggests a high volume of eruptions. Topography and tectonic history help us understand why larger eruptions might occur at one hotspot over another.