Principles of Nicolas Steno

Nicolas Steno
Principle of Superposition
In any sequence of undisturbed strata (rock layers), the oldest layer is on the bottom and the youngest is on the top.
Principle of Original Horizontality
Sediments settle from fluids under the influence of gravity, therefore the deposits are nearly horizontal or at very shallow inclines.
Principle of Lateral Continuity
A water-laid stratum, at the time it was formed, must continue laterally in all directions until it thins out as the result of nondeposition or until it abuts against the edge of the original basin of deposition.

Neptunism

Abraham Werner
Stated that all rocks of the Earth's crust were deposited from an ocean which once covered the entire surface.
Followers of this theory were known as Neptunists.

Plutonism

Plutonists, after observing volcanic eruptions, held that rocks were formed from the fires within the Earth.
Rocks are formed in both ways - in the oceans and in the Earth's interior.

Uniformitarianism

James Hutton
Believed in a dynamic Earth
Uniformitarianism - Understanding the present is the key to unlocking the past.
Processes occurring today also occurred in the past.

Principles of Charles Lyell

Principles of Geology
Principle of Cross-cutting Relations
A geologic feature which cuts across or penetrates another feature must be younger than what it cuts.
Principle of Inclusions
Rocks which contain inclusions of another rock are younger than the inclusion.
The inclusion is older than the rock in which it is included.

Principle of William Smith

Principle of Biologic Succession
Fossils found in one rock layer will differ from layers above and below.
By determining the sequence of fossils in one location, it is possible to correlate rocks from another location if they contain the same fossils.

Evolution

Charles Darwin - Alfred Russel Williams
Theory of Evolution - Natural Selection
Individuals within a species with favorable adaptations or mutations will have the best chance of survival.
Those that survive will transmit those favorable traits to the next generation.
"Survival of the Fittest"
Survival of the most suitably adapted.

Principles

Superposition
Original Horizontality
Lateral Continuity
Uniformitarianism
Cross-cutting Relations
Inclusions
Biologic Succession
Evolution

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