What is the geologic time scale?
Q: What is the geologic time scale?
A: The geologic time scale is a system used to measure and categorize the history of Earth's rocks and fossils. It divides Earth's history into different periods, eras, and epochs based on the relative positions of different strata and fossils.
Q: Who first proposed the principles behind the geologic time scale?
A: Nicolaus Steno was the first to propose the principles behind the geologic time scale in the late 17th century. He argued that rock layers (or strata) are laid down in succession, and that each represents a "slice" of time. He also formulated what is known as Steno's Principle of Superposition which states that any given stratum is probably older than those above it and younger than those below it.
Q: What theory did Abraham Werner propose about rocks?
A: Abraham Werner proposed a theory that all rocks had precipitated out of a single enormous flood, which was called Neptunist theory.
Q: Who introduced an alternative idea about how land forms?
A: James Hutton introduced an alternative idea about how land forms with his Theory of the Earth; or, an Investigation of the Laws Observable in the Composition, Dissolution, and Restoration of Land Upon the Globe before Royal Society of Edinburgh in 1785. His Plutonist theory suggested that land was eroded by air and water and deposited as layers in sea; heat then consolidated sediment into stone, uplifting it into new lands.
Q: What technique did William Smith pioneer for identifying strata?
A: William Smith pioneered a technique for identifying strata by their fossils content. By studying sequences of strata he realized they could be used to determine when certain events occurred during Earth's history.
Q: How did radiometric dating help refine geological understanding?
A: Radiometric dating helped refine geological understanding by providing absolute dates for rocks which allowed scientists to more accurately estimate when certain events happened during Earth's history such as when oxygen appeared in our atmosphere or when sexual reproduction evolved among organisms on our planet.
