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.
Pre-Columbian era
The Woodland period of North American pre-Columbian cultures refers to the time period from roughly 1000 BCE to 1000 CE. The term "Woodland" was coined in the 1930s and refers to prehistoric sites between the Archaic period and the Mississippian cultures. The Adena culture and the ensuing Hopewell tradition during this period built monumental earthwork architecture and established continent-spanning trade and exchange networks.