Final answer:
The discovery of ancient sea life fossils on dry land and the stratification of rock layers both helped promote the idea of Earth having a deep past. These, along with signs of historic geological activities, point to a long history of Earth’s evolution.
Step-by-step explanation:
Two key items that puzzled researchers and encouraged the idea that the Earth has a deep past are:
- Fossils of ancient sea life found on dry land far from current oceans. This discovery suggested that the Earth experienced significant changes over time, like land that is now dry once being submerged beneath the sea.
- The stratification of rock layers, which provided a means to trace Earth's and life's history. The order in which rocks and fossils appear in these layers reveals a long chronology of geological and biological evolution.
In addition to these, the evidence of ancient geological activity, such as volcanic eruptions, earthquakes, and erosion, also conveyed that Earth's surface has been shaped over vast spans of time. The formation of Earth's molten surface solidifying, and the presence of old photosynthetic cyanobacteria like stromatolites, align with the concept of a very ancient Earth, further reinforcing the idea of an extensive and deep history.