Final answer:
Nicolas Steno developed the law of superposition, which is used in relative dating to determine the relative ages of rocks and fossils. James Hutton proposed the idea of gradual change in Earth's geologic features, challenging the prevailing view of catastrophic events.
Step-by-step explanation:
Nicolas Steno (1638-1686): Nicolas Steno developed the law of superposition in the 17th century. This law states that in layers of horizontal sedimentary rocks, the oldest rock layer is at the bottom, and the youngest is at the top. This principle is used in relative dating to determine the relative ages of rocks and fossils.
James Hutton (1726-1797): James Hutton was a Scottish geologist who proposed the idea of gradual change in Earth's geologic features. He believed that geological change occurred gradually over long periods of time, in contrast to the prevailing view of catastrophic events. Hutton's ideas, along with the principle of uniformitarianism advocated by Charles Lyell, influenced our understanding of the vast scale of geologic time and the processes that shape the Earth.