1.3 Catastrophism, Gradualism and Uniformitarianism Flashcards
What is meant by the term catastrophism?
The theory that changes in the Earth’s crust during geological history have resulted from sudden violent and unusual short-lived events.
What is meant by the term gradualism?
The theory that assumes that change comes about gradually or that variation is gradual in nature. It is a model applied especially in evolution where one species is transformed into another by slow changes.
What is meant by the term uniformitarianism?
This theory maintains that slow, incremental changes such as erosion created all the Earth’s geological features. It holds that** the present is the key to the past**: that the geological processes observable now were acting in the same way in the past.
What does the abbreviation Ma mean?
It refers to a date before the present, in millions of years.
What does the abbreviation My or myr mean?
It is used for the duration of an event in millions of years.
What was James Hutton’s major contribution to geology?
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He proposed the basic rock cycle and was the first to have an awareness of the great age of the Earth.
What did Hutton suggest was the driving force for mountain building and volcanism?
The great heat and pressure within the planet (he was inspired by Watt’s steam engine).
What was Charles Lyell’s greatest contribution to geology?
He popularised the theory of uniformitarianism.
What is ‘Hutton’s unconformity’?
An arrangement of rocks (originally observed at Siccar Point) where ancient rocks had been uplifted, tilted, eroded and subsequent layers deposited on top.
What was the main limitation of Hutton’s rock cycle compared to our modern understanding?
There was no understanding of the mechanisms for mountain building and no awareness of subduction.
What was William Smith’s main contriubtion to geology?
He made a map of the geology of Great Britain. He also was the first to recognise that fossils occurred grouped in layers and that particular fossil faunas succeeded one another in a definite order (the beginnings of an understanding of evolution and dating rocks using fossils: biostratigraphy).
Why is it appropriate to consider both catastrophism and gradualism as valid theories?
Most of Earth’s geological features form through gradual processes but there are catastrophic events that can cause large magnitude changes e.g. asteroid impacts, volcanic eruptions and megafloods.
