Required Reading 1 & 2

Geological Time

Phanerozoic Eon: Cenozoic Era

  • Contains murals at the Smithsonian displaying mammals that ruled the Earth during the Miocene Epoch.

Introduction to the Cenozoic Era

  • Cenozoic Era: Started approximately 65 million years ago and continues to the present day.

  • Follows the Cretaceous-Paleogene extinction event, which was a significant extinction event that wiped out approximately 75% of species, including the non-avian dinosaurs.

  • The term "Cenozoic" translates to "recent life" in Greek and was introduced by British geologist John Phillips in 1840.

  • The era is divided into three main periods:

    • Paleogene Period (65-23 million years ago): Consists of three epochs: Paleocene, Eocene, and Oligocene. This period saw the rise of mammals and birds and the establishment of modern ecosystems.

    • Neogene Period (23-2.6 million years ago): Includes the Miocene and Pliocene epochs, characterized by the further evolution of fauna and flora, significant changes in sea levels, and the development of the modern global climate.

    • Quaternary Period (2.6 million years ago to present): Comprising Pleistocene and Holocene epochs, the current climate conditions can trace their origins to this period. Furthermore, there is ongoing debate regarding whether we have entered the Anthropocene Epoch, a proposed period characterized by the significant human impact on Earth's geology and ecosystems.

Climate and Geography of the Cenozoic Era

  • The climate during the early Cenozoic was notably warmer than present conditions, with a tropical global climate.

  • The Paleocene–Eocene Thermal Maximum was a critical period of intensive global warming around 55.8 million years ago, followed by a prolonged cooling phase.

  • Climate variability was significant throughout the Cenozoic era:

    • Paleogene: Dominated by tropical climates conducive to diverse life forms.

    • Neogene: Witnessed drastic cooling trends leading into the Pleistocene, transforming ecosystems and biodiversity.

Changing Landscape

  • Continental drift played a fundamental role during this era, creating expansive oceans that significantly affected marine life and biodiversity.

  • During the Pleistocene Epoch, glaciers blanketed central North America, which shaped the land by forming the Great Lakes as they receded, fundamentally altering the landscape.

  • Significant mountain ranges, such as the Alps, Himalayas, and Rockies, formed throughout the Cenozoic Era due to tectonic movements.

  • This era is often referred to as The Age of Mammals, following the extinction of many giant terrestrial and marine species and leading to the diversification of smaller mammals into various niches.

  • Key species during this period demonstrate a transition from survivors of the Cretaceous toward a profusion of diverse forms, including rhinoceroses, elephants, sabre-toothed cats, and woolly mammoths.

  • Plant life thrived in the absence of dinosaurs, enabling the rise and establishment of modern forests and unique plant species.