An ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere.
Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years.
romance and dating sites - Carbon dating tree buried in layers
Seriation uses the assumption that once a tool was developed, its use would become more widespread.
Stratigraphy uses the assumption that higher layers or strata were laid down after lower layers.
Ice cores showed the age of a military plane buried in the artic as thousands of years old.
Similarly, dendrochronology measures the tree rings in trees and assumes they represent years.
ANSWER: Relative dating is used to determine the relative ages of geologic strata, artifacts, historical events, etc.