Slow processes shape earth. Quantitative scientific methods. In 1897, Lord Kelvin assumed that the Earth was originally molten and calculated a date based on cooling through conduction and radiation. Age of Earth was calculated to be about 24-40 million years. River water has only a small concentration of salts.
Rivers flow to the sea.
Evaporative concentration of salts. Age of Earth was calculated to be 90-100 million years. In 1860, calculated to be about 3 million years old. In 1910, calculated to be about 1.6 billion years old. At this rate, the age of the first fossiliferous rocks is about 500 million years.