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It covers roughly 539 million years. During this period continents drifted apart, but eventually collected into a single landmass known as Pangea, before splitting again into the current continental landmasses. [citation needed] The Phanerozoic is divided into three eras – the Paleozoic, the Mesozoic and the Cenozoic.
The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet. Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs.
The evolution of life in this time reflected the conditions created by the assembly of Pangaea. The union of most of the continental crust into one landmass reduced the extent of sea coasts. Increased erosion from uplifted continental crust increased the importance of floodplain and delta environments relative to shallow marine environments.
A continent is a large geographical region defined by the continental shelves and the cultures on the continent. [1] In the modern day, there are seven continents. However, there have been more continents throughout history. Vaalbara was the first supercontinent. [2] Europe is the newest continent. [3]
c. 2.58 Ma – start of the Pleistocene epoch, the Stone Age and the current Quaternary Period; emergence of the genus Homo. Smilodon, the best known of the sabre-toothed cats, appears. c. 2.4 Ma – The Amazon River takes its present shape in South America. c. 2.0–1.5 Ma – The basin of the Congo River acquires its present shape.
The supercontinent Columbia, or Nuna, formed 2.1–1.8 billion years ago and broke up about 1.3–1.2 billion years ago. [48] [49] The supercontinent Rodinia is thought to have formed about 1300-900 Ma, to have included most or all of Earth's continents and to have broken up into eight continents around 750–600 million years ago. [50]
The history of paleontology traces the history of the effort to understand the history of life on Earth by studying the fossil record left behind by living organisms. Since it is concerned with understanding living organisms of the past, paleontology can be considered to be a field of biology, but its historical development has been closely tied to geology and the effort to understand the ...
The geologic time scale is divided into chronostratigraphic units and their corresponding geochronologic units. An eon is the largest geochronologic time unit and is equivalent to a chronostratigraphic eonothem. [13] There are four formally defined eons: the Hadean, Archean, Proterozoic and Phanerozoic. [2]