Cryptic (geology)
The Cryptic era is an informal term for the earliest geologic evolution of the Earth and Moon. It is the oldest (informal) era of the Hadean eon, and it is commonly accepted to have begun close to 4533 million (about 4.533 billion) years ago when the Earth and Moon formed. No samples exist to date the transition between the Cryptic era and the following Basin Groups era for the Moon (see also Pre-Nectarian), though sometimes it is stated that this era ended 4150 million years ago for one or both of these bodies. Neither this time period, nor any other Hadean subdivision, has been officially recognized by the International Commission on Stratigraphy.
The Hyborian Age
The essay sets out in detail the major events of Howard's pseudohistorical prehistory, both period before and after the time of the Conan stories. In describing the cataclysmic end of the Thurian Age, the period described in his Kull stories, Howard links both sequences of stories into one shared universe. The names he gives his various nations and peoples of the age borrow liberally from actual history and myth. The essay also sets out the racial and geographical heritage of these fictional entities, making them progenitors of modern nations. For example, Howard makes the Gaels descendants of his own Cimmerians.