Final answer:
Darwin explained the fossils of marine animals at high elevations as resulting from geological events that raised portions of the sea floor. His observations of fossils and reading of geology texts helped develop his theory of evolution through natural selection.
Step-by-step explanation:
Charles Darwin explained his observation of fossils of marine animals found several thousands of feet above sea level by concluding that geological events, such as earthquakes and the uplifting of land, caused the ancient sea floor to rise to a higher elevation. During his voyage on the HMS Beagle, Darwin observed rock layers containing marine fossils high in the Andes Mountains and experienced an earthquake that lifted the ocean floor. Along with the evidence of the fossil record, which showed changes in the forms and distribution of life over time, Darwin was influenced by the works of geologists like Charles Lyell, who suggested that Earth was much older than previously thought and that its surfaces changed over time due to slow, steady processes. These observations served as a foundation for Darwin's theory of evolution by natural selection, demonstrating that earth's surface and living organisms change over time.