© S. Quane and B. Andrews/Smithsonian InstitutionLAVA BUBBLES Researchers have discovered a new kind of ash, dubbed bread-crust bubbles, which are tiny spheres of ash no more than a millimeter in diameter that form deep underground.
Bread-crust bubble
Bred krəst ˈbəb(ə)l n.
Tiny, gas-filled beads of volcanic ash with a scaly surface.
Scientists have identified a
new type of volcanic ash that
erupted from a volcano in central Oregon roughly 7 million years ago. The particles are
similar to larger bread-crust bombs, which form as gases trapped inside globs of lava expand, cracking the bombs' tough exterior. Bread-crust bubbles,
each no more than a millimeter wide, have a distinctly crackled surface that can reveal secrets about how volcanoes erupt, researchers reported November 4 at the Geological Society of America annual meeting in Indianapolis.
The researchers had been sifting through other types of volcanic ash in the lab when they spotted the strange ash formations. Viewing the bits of ash through a scanning electron microscope revealed their crusty texture, indicating the gas bubbles
expanded rapidly on their way up to Earth's surface, but did not pop. Analysis of the texture also indicated the bubbles' depth when they first exploded in the foamy magma. In the case of the Oregon sample, says volcanologist Ben Andrews of the Smithsonian Institution in Washington D.C., the frothy ash
formed roughly 500 to 2,000 meters deep - a short distance, geologically - and erupted from the volcano at a rate of about 30 to 80 meters per second.
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To listen to part 2 of the interview, see: Adapt 2030 Ice Age Report: Interview with Laura Knight-Jadczyk and Pierre Lescaudron (Part 2)