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Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words smoke and fog [ 1 ] to refer to smoky fog due to its opacity, and odor. [ 2 ] The word was then intended to refer to what was sometimes known as pea soup fog, a familiar and serious problem in London ...
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth itself.
Mineral evolution. Most minerals on Earth formed after photosynthesis by cyanobacteria (pictured) began adding oxygen to the atmosphere. Mineral evolution is a recent hypothesis that provides historical context to mineralogy. It postulates that mineralogy on planets and moons becomes increasingly complex as a result of changes in the physical ...
The rock cycle explains how the three rock types are related to each other, and how processes change from one type to another over time. This cyclical aspect makes rock change a geologic cycle and, on planets containing life, a biogeochemical cycle. Structures of Igneous Rock. Legend: A = magma chamber (batholith); B = dyke /dike; C = laccolith ...
The geochemistry of carbon is the study of the transformations involving the element carbon within the systems of the Earth. To a large extent this study is organic geochemistry, but it also includes the very important carbon dioxide. Carbon is transformed by life, and moves between the major phases of the Earth, including the water bodies ...
Ground-level ozone. Seasonal average vertical columns of tropospheric ozone in Dobson units over the period 1979 to 2000. In June to August, photochemical ozone production causes very high concentrations over the East Coast of the US and China. Ground-level ozone (O3), also known as surface-level ozone and tropospheric ozone, is a trace gas in ...
Late heavy bombardment of the Moon (and probably of the Earth as well) by bolides and asteroids, produced possibly by the planetary migration of Neptune into the Kuiper belt as a result of orbital resonances between Jupiter and Saturn. [5] "Remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia.