Bubbles happen. And sometimes they are awesome.
Here is a bubble that formed inside of sea salt in a solution that a student at Finland’s Tampere University of Technology was making.
Gas pockets also form naturally in halite (rock salt). These are even more awesome because this air is the atmosphere as it was back in the day, not what we have today. Such air bubbles allow Earth scientists to directly study conditions in the distant past.
This recently made the news when researchers analyzed 800-million-year-old air found in Australian halite and found more oxygen than they expected. The discovery could change our understanding of how early animals evolved.
Inclusions have been found in volcanic rocks, too.
Molten rock degasses–this is why volcanologists measure CO2, sulfur, and other gases on a sleeping volcano. As magma rises toward the surface, those gas levels increase. It’s a way to see inside the volcano before it erupts.
Some gas remains in lava after it has erupted. There isn’t much and it’s not as easy to measure as a gas bubble, since what was once molten rock is now frozen. This is why melt inclusions are solid and glassy. (Oppenheimer)
Nevertheless, there is sometimes enough gas left for scientists to get an idea of how much climate-changing gases an ancient eruption released. (Self and Rampino)
For instance, one reason the Deccan Traps flood basalt in India is sometimes associated with the dinosaur-killing K-Pg mass extinction (in addition to the asteroid impact) is because its eruption may have released at least 200 times as much sulfur as the 1991 eruption of Mount Pinatubo (Oppenheimer), whose sulfur cloud cooled the world 1 degree Fahrenheit between 1991 and 1993.
Melt inclusions also convey a lot of information about the physical conditions at the source of the magma they formed in, many miles below our feet.
And then there are Hadean zircons. These small crystals found in igneous rock contain information that is changing how we picture the very early Earth.
Mineral inclusions in antarctic zircons also provide clues about what was going on back in the Hadean.
Perhaps the biggest inclusion-related surprise for geoscientists is the discovery of tistarite–a very rare titanium-based mineral–in melt inclusions found in rock that was erupted during the Cretaceous in what is now northern Israel.
How rare is it? Tistarite formed along with the Solar System and only one grain of it has been found in a meteorite. No one suspected there was any on Earth.
Now it looks like geologists may have to rewrite their textbooks on the deep Earth’s geochemistry!
Featured image: Eurico Zimbres. CC BY-SA 2.5.
Oppenheimer, C. 2011. Eruptions That Shook the World. Cambridge: Cambridge University Press. Retrieved from https://play.google.com/store/books/details?id=qW1UNwhuhnUC
Self, S., and Rampino, M. 2012. Flood basalts, mantle plumes and mass extinctions. The Geological Society. https://www.geolsoc.org.uk/flood_basalts_1 Last accessed March 23, 2018.