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The mesosphere (/ ˈ m ɛ s ə s f ɪər, ˈ m ɛ z-, ˈ m iː s ə-,-z ə-/; [1] from Ancient Greek μέσος (mésos) 'middle' and -sphere) is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as altitude increases.
The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia.
Earth is the only place in the universe known to harbor life, where it exists in myriad environments. [8] [9] The origin of life on Earth was at least 3.5 billion years ago, possibly as early as 3.8-4.1 billion years ago. [2] [3] [4] Since its emergence, life has persisted in several geological environments.
Mesoamerica and its cultural areas. Mesoamerica is a historical region and cultural area that begins in the southern part of North America and extends to the Pacific coast of Central America, thus comprising the lands of central and southern Mexico, all of Belize, Guatemala, El Salvador, and parts of Honduras, Nicaragua and Costa Rica.
Territorial evolution of Mexico from 4 October 1824 to 8 October 1974 Map of Mexico in 1828. Mexico has experienced many changes in territorial organization during its history as an independent state. The territorial boundaries of Mexico were affected by presidential and imperial decrees.
Map of early human migrations based on the Out of Africa theory; figures are in thousands of years ago (kya). [2]The peopling of the Americas began when Paleolithic hunter-gatherers (Paleo-Indians) entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the ...
Aztec calendar (sunstone) Mesoamerican chronology divides the history of prehispanic Mesoamerica into several periods: the Paleo-Indian (first human habitation until 3500 BCE); the Archaic (before 2600 BCE), the Preclassic or Formative (2500 BCE – 250 CE), the Classic (250–900 CE), and the Postclassic (900–1521 CE); as well as the post European contact Colonial Period (1521–1821), and ...
This is a list of Global Boundary Stratotype Sections and Points. Since 1977, Global Boundary Stratotype Sections and Points (abbreviated GSSPs) are internationally agreed upon reference points on stratigraphic sections of rock which define the lower boundaries of stages on the geologic time scale .