User:Abyssal/Portal:Quaternary

The Quaternary prehistory Portal

Introduction

The Quaternary (/kwəˈtɜːrnəri/ kwə-TUR-nər-ee, US also /ˈkwɒtərnɛri/ KWOT-ər-nerr-ee) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the Phanerozoic eon. It follows the Neogene Period and spans from 2.6 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene (2.6 million years ago to 12 thousand years ago) and the Holocene (12 thousand years ago to today); a proposed third epoch, the Anthropocene, was rejected in 2024 by International Union of Geological Sciences (IUGS), the governing body of the International Commission on Stratigraphy (ICS).

The Quaternary is typically defined by the Quaternary glaciation, the cyclic growth and decay of continental ice sheets related to the Milankovitch cycles and the associated climate and environmental changes that they caused. (Full article...)

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Lōʻihi Seamount is an active submarine volcano located around 35 km (22 mi) off the southeast coast of the island of Hawaiʻi about 975 m (3,000 ft) below sea level. This seamount lies on the flank of Mauna Loa, the largest shield volcano on Earth. Lōʻihi meaning "long" in Hawaiian, is the newest volcano in the Hawaiian-Emperor seamount chain, a string of volcanoes that stretches over 5,800 km (3,600 mi) northwest of Lōʻihi. Unlike most active volcanoes in the Pacific Ocean that make up the active plate margins on the Pacific Ring of Fire, Lōʻihi and the other volcanoes of the Hawaiian-Emperor seamount chain are hotspot volcanoes and formed well away from the nearest plate boundary. Volcanoes in the Hawaiian Islands arise from the Hawaiʻi hotspot, and as the youngest volcano in the chain, Lōʻihi is the only Hawaiian volcano in the deep submarine preshield stage of development.

Lōʻihi began forming around 400,000 years ago and is expected to begin emerging above sea level about 10,000–100,000 years from now. At its summit, Lōʻihi Seamount stands more than 3,000 m (10,000 ft) above the seafloor, making it taller than Mount St. Helens was before its catastrophic 1980 eruption. The summit is currently 975 m (3,000 ft) below sea level. A diverse microbial community resides around Lōʻihi's many hydrothermal vents. (see more...)

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The Tree of Life as depicted by Ernst Haeckel in The Evolution of Man (1879) illustrates the 19th-century view that evolution was a progressive process leading towards man. — The Tree of Life as depicted by Ernst Haeckel in *The Evolution of Man* (1879) illustrates the 19th-century view that evolution was a progressive process leading towards man.

Evolutionary thought, the conception that species change over time, has roots in antiquity. With the beginnings of biological taxonomy in the late 17th century, a new anti-Aristotelian approach to modern science challenged traditional essentialism. Naturalists began to focus on the variability of species; the emergence of paleontology with the concept of extinction further undermined the static view of nature. In the early 19th century, Jean-Baptiste Lamarck proposed the first fully formed theory of evolution.

In 1858, Charles Darwin and Alfred Russel Wallace published a new evolutionary theory that was explained in detail in Darwin's On the Origin of Species (1859). Unlike Lamarck, Darwin proposedcommon descent and a branching tree of life. The theory was based on the idea of natural selection, and it synthesized a broad range of evidence from animal husbandry, biogeography, geology, morphology, and embryology.

The debate over Darwin's work led to the rapid acceptance of the general concept of evolution, but the specific mechanism he proposed, natural selection, was not widely accepted until it was revived by developments in biology that occurred during the 1920s through the 1940s. Before that time most biologists argued that other factors were responsible for evolution. The synthesis of natural selection with Mendelian genetics during the 1920s and 1930s founded the new discipline of population genetics. Throughout the 1930s and 1940s, population genetics became integrated with other biological fields, resulting in a widely applicable theory of evolution that encompassed much of biology—the modern evolutionary synthesis. (see more...)

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Artist's restoration of a Smilodon.
Image credit: Sergiodlarosa

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Did you know?

... that the extinct Jamaican Flightless Ibis developed unique club-like wings that could be used as a flail?
... that the extinct crocodile Rimasuchus often preyed on large mammals, including early humans?
... that the Ph.D dissertation of taphonomist Kay Behrensmeyer suggested that sauropods were terrestrial?
... that the extinct New Zealand Musk Duck was becoming more sedentary than its closest relative, the Australian Musk Duck?
... that fossils of 23 mammal species including mammoth, dire wolf, giant ground sloth, pre-historic bison, camel, and horse have been found at Fossil Lake in south central Oregon?