Historical geology Reference Libraries
Rainforests are forests that are characterized by high levels of rainfall, with definitions based on a minimum usual annual rainfall of about 68 to 78 inches. The monsoon trough, or otherwise known as the intertropical convergence zone, holds an important role in producing the climatic conditions that are essential for the Earth’s tropical rainforests. About 40 to 75 percent of all biotic...
Climate change is a substantial and lasting change in the statistical distribution of weather patterns over periods of time ranging from decades to millions of years. It might be a change in the average weather conditions, or in the distribution of weather around the average conditions. Climate change is a result of factors that include oceanic processes, biotic processes, variations in solar...
The Neoproterozoic is the third of three subdivisions of the Proterozoic Eon (occurring from 1 billion years ago to 542 million years ago). This terminal era of the Proterozoic is itself divided into three sub-periods called the Tonian, Cryogenian, and Ediacaran Periods. The most severe glaciation known in the geologic record occurred during the Cryogenian Period, when ice sheets reached the...
The Paleoproterozoic is the first of three subdivisions of the Proterozoic Eon (occurring from 2.5 billion to 1.6 billion years ago (Ga). This period is marked by the first stabilization of the continents, and also when cyanobacteria--a type of bacteria that uses biochemical processes of photosynthesis to produce oxygen--evolved. Experts have found paleontological evidence that during at...
The Archean (formerly Archaeozoic) is a geologic eon between the Hadean and Proterozoic eons. The Archean Eon begins at roughly 3.8 billion years ago (Ga) and ends at about 2.5 Ga. But unlike all other geological ages, which are based on stratigraphy, The Archean eon is defined chronometrically. The lower boundary of 3.8 Ga has also not been officially recognized by the International Commission...
The Hadean is the unofficial geological period of time that lies just before the Archean time period. The Hadean began with the formation of the Earth roughly 4.5 billion years ago (Ga) and ended about 3.8 Ga; the latter date varies according to different sources. Hadean is derived from Hades, Greek for “underworld,” referring to the hellish conditions on the planet at the time. The term...
Alfred Lothar Wegener (November 1, 1880 "“ November 2, 1930) was a German scientist, geologist, and meteorologist. He is best known for establishing the theory of the continental drift. His 1915 theory of continental drift surmised that the continents were slowly floating around the Earth. Most of his basis was strictly circumstantial evidence, and further he was not able to exhibit a...
