-a relative scale. Being around for longer than absolute ages. -uniformitarianism. Geology gave Darwin time for natural selection (Hutton & Lyell). -early age estimates of Earth from seawater and rocks cooling. -can be traced back to Nicholas Steno, the father of stratigraphy.
-stratification is the layering that is diagnostic for sedimentary rocks.
A broken sequence between two rock layers or a gap in geologic time.
Between two sedimentary layers.
Between a sedimentary rock and underlying igneous rock or metamorphic rock.
Two rock layers (regardless of rock type) not parallel to each other.