An impact of cosmic proportions
Around 14.8 million years ago, an asteroid with a diameter of approximately 1.5 kilometers entered Earth's atmosphere. Traveling at a velocity of more than 70,000 kilometers per hour, it struck the surface in what is now Bavaria, Germany. The impact released energy equivalent to roughly 1.8 million Hiroshima bombs, creating the 24-kilometer-wide Nördlinger Ries crater.
The event was catastrophic. Temperatures at the point of impact reached up to 30,000° Celsius, instantly vaporizing the asteroid and about 3 cubic kilometers of surface rock. A superheated jet of molten rock and gas was ejected high into the atmosphere, traveling at several kilometers per second. This material, a combination of terrestrial sediments and meteorite fragments, was thrown hundreds of kilometers to the northeast. The entire impact sequence, from collision to the settling of ejecta, lasted only a few minutes.
A rain of green glass
As the molten ejecta traveled through the upper atmosphere, it rapidly cooled and solidified into a natural glass, a type of tektite. This rapid quenching prevented the formation of a crystalline structure, resulting in an amorphous glass. These green, glassy objects rained down over a "strewn field" covering parts of modern-day South Bohemia and Moravia in the Czech Republic. The total estimated weight of moldavite created was between 275 and 300 tons.
Moldavite's chemical formula is primarily silicon dioxide (SiO2) with aluminum oxide (Al2O3) and smaller amounts of iron, potassium, and calcium oxides. Its distinctive green color is due to its iron content. Each piece is unique, with surfaces sculpted by its fiery passage through the atmosphere and, later, by millions of years of etching from acidic groundwater.
A definitive characteristic of genuine moldavite is the presence of lechatelierite, worm-like inclusions of pure fused quartz glass that formed under the extreme temperature and pressure of the impact. Many pieces also contain tiny, elongated bubbles of gas trapped at very low pressure, evidence of their formation high in Earth's atmosphere.