Michelle Shocked | quartz | Quartz | Short Sharp Shocked | Quartz (publication) | Quartz (graphics layer) | Fused quartz | fused quartz | City of Quartz |
The main evidence for the Alvarez hypothesis that a single impact resulted in the Cretaceous–Paleogene extinction event that killed the dinosaurs has come from the presence around the world of shocked quartz granules, glass spherules and tektites embedded in a layer of clay with extremely high levels of iridium, all signs of an asteroid impact.