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.
Superposition of rock units is a very simple and straightforward method of relative age determination.
The principle states that in a sequence of undeformed sedimentary rocks the oldest beds are at the bottom and the youngest ones are at the top.
If a geologist claims to be 45 years old, that is an absolute age.
Superposition: The most basic concept used in relative dating is the law of superposition.
The Scottish geologist James Hutton (1726-1797) argued that granite and basalt by solidification within the earth (as opposed to precipitating in from oceanwater).
is a way to use geometric relationships between rock bodies to determine the sequence of geologic events in an area.
Relative dating is different from absolute dating in which specific dates are assigned to geologic events (we will discuss absolute dating techniques later).
Underlying assumptions are 1) that Faunal Succession is based on the observation that animals and animal communities that are preserved in sedimentary rocks change noticeably as geologic time passes (evolution).
It was first recognized by William Smith, a British Surveyor, who while working on open cuts of canals, railroads, and roads, noticed that the fossils change systematically from the older towards the younger rocks.