Final answer:
Geologists use rock layers, fossils, and dating methods like relative and absolute dating, to theorize Earth's pre-human history. They leverage principles such as uniformitarianism to infer those slow geological processes over vast time periods shaped the Earth's surface.
Step-by-step explanation:
Geologists formulate theories about Earth's pre-human events by analyzing the geological record, which includes rock layers, fossils, and other environmental indicators. By studying these elements, they can reconstruct the sequence of geological events and understand the processes that formed the Earth's surface.
Fossils of ancient sea life on dry land far from oceans suggest changes over geological timelines, indicating that certain land was once under the sea. The many layers of rock demonstrate the order in which rocks and fossils appeared, aiding in tracing Earth's history and life development. Furthermore, evidence of past volcanic eruptions, earthquakes, and erosion indicates an older Earth formed by processes occurring over vast periods.
Relative dating and absolute dating are two methods used by geologists. Relative dating establishes a timeline of events without exact dates, while absolute dating uses radioactive isotopes to determine the numerical ages of rocks and minerals. The principle of uniformitarianism, pioneered by Charles Lyell, posits that the geological processes we observe today have operated similarly in the past. This concept signifies that for the gradual changes we see to form significant geological features, the Earth must be much older than once thought.