Numerical age dating geology
You may have already completed introductory laboratory studies of igneous, sedimentary, and metamorphic rocks.
If so, you have already practiced interpreting details of earth's history from the evidence contained in rocks.
The idea of uniformitarianism is that the laws and principles that nature follows in today's world, such as gravity, also applied in the geologic past; in other words, "the present is the key to the past." The idea of uniformitarianisms is commonly misinterpreted in two different ways.
The first incorrect interpretation is that it states that only slow changes occur on earth, the second misinterpretation is that it states that catalclysmic events cannot have happened in the past.
Geologists still use Steno's principles, with some refinements and additions.
They are summarized as the principles of relative geologic age determination, sometimes referred to as the principles of relative dating.
By using the principles of relative geologic age, the sequence of geologic events -- what happened first, what happened next, what happened last -- can be established.
In the early 1800s, soon after James Hutton died, William Smith in England made the scientific case for what came to be called the principle of faunal succession.
The key to this principle is that during a specific geologic time, only certain types of organisms existed, so if fossils of those organisms are found in a layer of rock, the rock is of that geologic age, the age when those organisms were species that lived on earth.
A few centimeters a year, about the rate your fingernails grow, may not seem like much but, as millions of years of geologic time unfold, it adds up to thousands of kilometers .
Fast or slow, abrupt or taking millions of years, uniformitarianism includes natural processes of all different rates, from abrupt and cataclysmic to barely detectable and very slow.
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Lyell was a significant scientific presence through much of the time of Victorian England in the 1800s.