The dramatic increase in urban concentration began approximately in the 1930s.
Pleistocene glaciation (the southward movement of ice that began approximately 2.6 million years ago) scraped most of the land bare.
In terms of absolute time, the Carboniferous Period began approximately 358.9 million years ago and ended 298.9 million years ago.
The Ordovician period began approximately 490 million years ago, with the end of the Cambrian, and ended around 443 million years ago, with the beginning of the Silurian.
Between 1945 and 1948, the United States began approximately 50 independent cruise missile projects, but lack of funding gradually reduced that number to three by 1948.
Sediments formed under less-restricted drift conditions began approximately 125 million years ago and are younger to the north, where they are mostly represented by clastic marine deposits.
Before its intensive development began approximately 150 years ago, the mountainous portion of the peninsula was covered by coniferous forests, with mixed broadleaved forests confined to the coastal lowlands.
"The surge in poaching for ivory that began approximately a decade ago – the worst that Africa has experienced since the 1970s and 1980s – has been the main driver of the decline," said IUCN.
Most modern estuaries formed as the result of a worldwide rise in sea level, which began approximately 18,000 years ago during the waning phase of the Wisconsin Glacial Stage.
The Rolfing movement began approximately 40 years ago in America by Ida Rolf, Ph.D., and it reached the popular culture in the late 1960s through the Human Potential Movement that was active in California at the time.
Esophageal stricture began approximately 1 month after AEN (e).
