Cliffs, road cuts, and non-vegetated landscapes allow us glimpses into geology which is often hidden from view.
Cliffs and road cuts are "side views" or "geologic cross-sections" of the topography which show the relative positions of various rock layers and structures at a given spot.
Though radiometric dating offers a modern way to date rocks, the principles of stratigraphy remain a tried and true way to learn about rock layers.
Stratigraphy, or the scientific study of rock layers, includes relative dating.
To review our principles of relative dating as applied to such geologic cross-sections, we will make use of a neat learning tool available on the Internet.
"Athro Limited" is a private company which provides education modules on the Internet.
The secondary rocks were thought to include interlayered basalts, which Werner thought formed by combustion of buried coal layers.
The Scottish geologist James Hutton (1726-1797) argued that granite and basalt by solidification within the earth (as opposed to precipitating in from oceanwater).
(dark brown) Flat lying sedimentary rocks were eventually precipitated.This idea is known as Plutonism, in reference to the God of the deep underworld.Hutton viewed tilted strata as having been initially deposited horizontally, and then were subsequently deformed (tilted and folded) by the forces of Earth's internal heat engine.Just as Sherlock Holmes used his power of observation to decipher the clues to a suspect's past actions, we will let the blemishes and behaviors of the rocks tell us their past story. ) Remember that relative dating involves determining "which came first" rather than "exactly when did this happen." The first step to untangling the geologic history of an area is often to figure out what happened first, second and third, etc.without knowing the absolute ages at which the rocks themselves formed.