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Analysis of Zircon Crystals Leads to New View of Magma

When visualizing the interior of a volcano, one would imagine liquid magma trapped inside caverns of igneous rock. Recently volcanologists gained insight on the nature of magma reservoirs by analyzing zircon crystal remains from a volcano eruption in New Zealand. The eruption of Mount Tarawera occurred approximately 700 years ago and covered surrounding areas with millions of tons of ash and debris. Additionally, it brought lava to the surface which deposited in the reservoir.

Extreme temperatures and pressure damage equipment, making directly studying magma difficult. However, minerals such as zircon can record magma conditions prior to eruption. By studying the distribution of lithium in zircon crystals, the researchers determined the length of time the crystals were exposed to a range of 650 degrees to 750 degrees Celsius. At these temperatures, magma begins to melt, resembling the structure of a snow cone. Such assumptions were made possible due to lithium’s ability to diffuse through zircon more quickly at higher temperatures.

The results suggest that the magma melted a brief period before the eruption. The zircons resided in the magma reservoirs for tens of thousands of years. However, lithium diffusion revealed that the crystals spent approximately one thousand years at temperatures ranging from 650 degrees to 750 degrees Celsius. Additionally, the crystals spent much less time at temperatures exceeding 750 degrees Celsius—the temperature in which magma melts entirely. Therefore, the magma spent a majority of its lifetime in a mostly solid state, contrasting the previous notion that magma reservoirs are composed entirely of liquid.

In a volcano eruption, melted magma—less dense than surrounding rock—rises and builds up in magma reservoirs. After substantial amounts of time and pressure, the magma is forced through the Earth’s surface as lava. The recent discovery may assist volcanologists to determine when volcanoes pose the highest risk for an eruption.  However, the researchers hope to learn more regarding the complex process of magma mobilization.

 

To read original study, click here.

To learn more about volcano eruptions, click here.

 

Editor: Maria ‘Stefi’ Ticsa