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→Increasing ages
In 1854 [[Hermann von Helmholtz]] estimated an age of between 20 and 40 million years.<ref name="ingv" />
In 1854 [[Hermann von Helmholtz]] estimated an age of between 20 and 40 million years.<ref name="ingv" />
Around the same time [[Lord Kelvin]] put his mind to deriving an age, and came up with a range between 20 million years and 400 million years. He later refined that down to between 20 million and 40 million years.<ref name="ingv" />
Around the same time [[Lord Kelvin]] put his mind to deriving an age, and came up with a range between 20 million years and 400 million years. He later refined that down to between 20 million and 40 million years.<ref name="ingv" /> More recent discoveries of radioactivity and mantle convection explain why the assumptions Helmholtz and Kelvin made resulted in dates that are much lower than current uniformitarian estimates.
The 1911 edition of the [[Encyclopedia Britannica]] discussed dates up to 500 million years.<ref>Encyclopædia Britannica, pp 650-651.</ref>
The 1911 edition of the [[Encyclopedia Britannica]] discussed dates up to 500 million years.<ref>Encyclopædia Britannica, pp 650-651.</ref>