Start Radiometric dating of moon rocks

Radiometric dating of moon rocks

The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic."Evidence from radiometric dating indicates that Earth is about 4.54 billion years old.

He also formulated the law of superposition, which states that any given stratum is probably older than those above it and younger than those below it.

While Steno's principles were simple, applying them proved challenging.

Over the course of the 18th century geologists realized that: The Neptunist theories popular at this time (expounded by Abraham Werner (1749–1817) in the late 18th century) proposed that all rocks had precipitated out of a single enormous flood.

For example, in North America, the Lower Cambrian is called the Waucoban series that is then subdivided into zones based on succession of trilobites.

In East Asia and Siberia, the same unit is split into Alexian, Atdabanian, and Botomian stages.

This clock representation shows some of the major units of geological time and definitive events of Earth history.

The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga (billion years ago).

Geologists qualify these units as "early", "mid", and "late" when referring to time, and "lower", "middle", and "upper" when referring to the corresponding rocks.