Final answer:
Hot spots form a chain of volcanoes as Earth's tectonic plates move over stationary areas of intense heat in the mantle, such as the well-known Hawaiian hot spot that created the Hawaiian Island chain.
Step-by-step explanation:
A hot spot is an area in the mantle from which heat rises as a thermal plume from deep within the Earth. High heat and lower pressure at the base of the lithosphere (crust) facilitates the melting of rock, which forms magma that rises to the surface to create volcanic activity. As Earth's tectonic plates move over these stationary hot spots, a chain of volcanoes is formed. The Hawaiian hot spot is a famous example, where the movement of the Pacific Plate over millions of years has resulted in the formation of the Hawaiian Island chain.
The presence of hot spots can result in volcanic activity far from tectonic plate boundaries. For instance, the Hawaiian hot spot has produced one of the longest and most notable chains of volcanic islands, and the Yellowstone hot spot creates potential for significant volcanic eruptions. As for the massive volcanoes created by hot spots, they can rise significantly above the ocean floor and become some of the largest mountains on Earth, like Mauna Kea in Hawaii, also renowned as a premier astronomical observation site due to its high elevation and clear skies.