Geochemistry, Mineralogy, Volcanology Research Spotlight

What Led to the Largest Volcanic Eruption in Human History?

A mineral-dating project at the Toba caldera in Indonesia sheds light on the science of supereruptions.

Source: Geochemistry, Geophysics, Geosystems

By Sarah Witman

In the northern part of the Indonesian island of Sumatra lies the Toba caldera, a massive crater formed by what scientists think is the largest volcanic eruption ever experienced by humanity. The eruption, called the Youngest Toba Tuff supereruption, took place about 74,000 years ago.

By dating zircon, a diamond-like gemstone, and other minerals in the area such as quartz, Reid and Vazquez have pieced together clues about the activity of magma below the surface prior to the supereruption.

Zircon is the oldest dated mineral on Earth. With a hardness rating of 7.5, it is resistant to chemical and mechanical weathering and can withstand metamorphism (structural changes due to heat, pressure, and other natural processes). All of these factors make it an ideal mineral for geological dating, especially for magma. Because zircon does not gain or lose uranium or lead even at magmatic temperatures, zircon typically contains high uranium and low lead levels, and scientists may use the ratio of these two elements in the zircon to determine the age of the sample.

The way in which zircon crystals in the Youngest Toba Tuff magma appear to have nucleated and grown over time, the researchers found, provides evidence of intermittent changes in the composition of the underground body of magma that eventually erupted. Certain characteristics of the zircon also indicate repeated episodes of magma recharge—fresh influxes of magma that often trigger eruptions—occurring tens of thousands to hundreds of thousands of years before the supereruption.

The team’s findings are significant for modern-day humans, given that aerosols and ash that erupted from Youngest Toba Tuff are thought to have entered the atmosphere, causing global cooling and the near extinction of the human race. A supereruption of equal or greater magnitude today could therefore have similarly drastic consequences. By better understanding the conditions that led up to the Youngest Toba Tuff supereruption, scientists can help paint a clearer picture of the future. (Geochemistry, Geophysics, Geosystems, https://doi.org/10.1002/2016GC006641, 2017)

—Sarah Witman, Freelance Writer

Citation: Witman, S. (2017), What led to the largest volcanic eruption in human history?, Eos, 98, https://doi.org/10.1029/2017EO071343. Published on 13 April 2017.
© 2017. The authors. CC BY-NC-ND 3.0
  • Toba also erupted in the mid Pleisticene, synonymously with the Australia-Asian (AA) and coeval Belize tektite generating impact events, Java Man’s disappearance from Indonesia, right before the Brunhes-Matuyama geomag reversal, in the middle of the global climate cycle shift from ~40 to ~100 ka and the last great extinction (benthic foraminifera). Could all of these major and unexplained events actually be unrelated? Why has the Australasian impact structure, the source of ~60 billion tons of tektite melt strewn across 1/4 to 1/3 of Earth’s surface, not yet been found? Understanding these temporally related mysteries may be the key in avoiding their repetition. Toba science is important in the larger frame of understanding these mid-Pleistocene goings-on.

    • JS

      The impact location of the AA event is believed to be in the Bass straight separating Tasmania from Australia. As I understand it, lead tektites have been described in the Latest Cretaceous aged sandstones near Sydney that are believed to emanate from the lead deposits in northern Tasmania.

  • sunman42

    Oh, not to worry. We’d just burn more hydrocarbons to warm things up again. 🙁