Supereruption

Another study performed by Stanley Ambrose, a professor of anthropology at the University of Illinois in 1998, suggests that a bottleneck occurred in human evolution at around 70,000 years ago, coinciding with a volcanic winter following the Toba supereruption.

Though the causes and interactions remain incompletely understood, study of extinctions does show that life on Earth is fragile. Extinctions have occurred regularly throughout Earth history and all of life is vulnerable to the violent actions of this mobile planet and to the effects of giant meteorite impacts. A list of the five largest extinctions in Earth history is given in the table on page 1 08 . Many more of smaller magnitudes have occurred. In relatively small ways, earthquakes form hazards: The most deadly earthquake in recorded history took place in China’s Shaanxi province in 1556, killing 800,000 people. Volcanoes, on the other hand, can change the entire planet’s climate: 73,500 years ago a volcanic supereruption occurred in Sumatra, filling the atmosphere with sulfur, ash, and carbon dioxide, blocking the Sun’s energy to such an extent that plants couldn’t sufficiently photosynthesize, and the global ecosystem almost collapsed.

The Los Alamos mesa rested against the eastern slope of the Jemez Mountains, on the rime of the Valles Caldera, formed as a result of two explosive super-eruptions 1.6 and 1.1 million years ago.

All these lines of evidences (formation of giant calderas like 11-18 k, Oued Dar'a caldera in the Saghro massif, ignimbrites, and thick successions and ignimbrite flow unites without any intervening sedimentary units) point toward an occurrence of multiple supervolanoes/supereruptions (resembling the 74, 000 yr Toba event) during emplacement of the ca. 580 Ma pulse of the Central Iapetus magmatic province.