The 11th-century Persian geologist Avicenna (Ibn Sina, died 1037) and the 13th-century Dominican bishop Albertus Magnus (died 1280) extended Aristotle's explanation into a theory of a petrifying fluid.
In the late 17th century Nicholas Steno (1638–1686) pronounced the principles underlying geologic (geological) time scales.
In a similar way, the most recent era is expanded in the third timeline, and the most recent period is expanded in the fourth timeline.
Corresponding to eons, eras, periods, epochs and ages, the terms "eonothem", "erathem", "system", "series", "stage" are used to refer to the layers of rock that belong to these stretches of geologic time in Earth's history.
Older time spans, which predate the reliable fossil record (before the Proterozoic eon), are defined by their absolute age.
Geologic units from the same time but different parts of the world often look different and contain different fossils, so the same time-span was historically given different names in different locales.
This theory, known as "Plutonism", stood in contrast to the "Neptunist" flood-oriented theory.
In Ancient Greece, Aristotle (384-322 BCE) observed that fossils of seashells in rocks resembled those found on beaches – he inferred that the fossils in rocks were formed by living animals, and he reasoned that the positions of land and sea had changed over long periods of time.
Leonardo da Vinci (1452–1519) concurred with Aristotle's interpretation that fossils represented the remains of ancient life.
The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon.
Therefore, the second timeline shows an expanded view of the most recent eon.