Yeah no, Social Darwinism wasn't created by Darwin, nor was it a scientific theory. It was a misunderstanding of fitness as others have pointed out. Living things evolve to cooperate more often than fighting. Our very cells are proof of this. "free-living prokaryotic ancestors of modern mitochondria permanently fused with eukaryotic cells in the distant past, evolving such that modern animals, plants, fungi, and other eukaryotes are able to respire to generate cellular energy." https://www.annualreviews.org/doi/10.1146/annurev-micro-090817-062213
Geology was still quite nascent and radiometric dating was still many decades off. A few factors were erosion of large structures and rock formations. I would look at the earliest works of people like Lyell. When Darwin made the huge leap to common ancestry of ALL life he reasoned that going from a to b to where we are now would take immense amounts of time. I would finger through origins to see how he puts it.