Uniformitarianism

Uniformitarianism is a fundamental principle in geology that states that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe. It refers to the invariance in the metaphysical principles underpinning science, such as the constancy of causal structure throughout space-time, but has also been used to describe spatiotemporal invariance of physical laws. Though an unprovable postulate that cannot be verified using the scientific method, uniformitarianism has been a key first principle of virtually all fields of science.

History

The concept of uniformitarianism was first proposed by James Hutton in the late 18th century. Hutton's ideas were refined and popularized by Charles Lyell in the 19th century. Lyell's interpretation of geologic change as the steady accumulation of minute changes over enormously long spans of time was a powerful influence on Charles Darwin, who incorporated Lyell's principles into his theory of evolution.

Principles

Uniformitarianism is based on several principles:

• The principle of inclusion: This principle states that any geological feature that contains another is the younger of the two.
• The principle of cross-cutting relationships: This principle states that an igneous intrusion is always younger than the rock it cuts across.
• The principle of original horizontality: This principle states that layers of sediment are originally deposited horizontally under the action of gravity.

Criticism and Controversy

Uniformitarianism has been criticized for its assumption that the rate of geologic change is constant. Some scientists argue that catastrophic events, such as meteor impacts or massive volcanic eruptions, have played a significant role in Earth's history. This has led to the development of catastrophism, a theory that emphasizes the role of rare, high-magnitude events in the geological record.

See Also

• Catastrophism
• Geology
• James Hutton
• Charles Lyell