Diatoms and Diatomaceous Earth, Part 1

Diatoms—microscopic, photosynthetic algae with intricate, glass-like silica shells called frustules—are not just biological curiosities; they are planetary powerhouses, responsible for 20–30% of Earth's oxygen and 45% of oceanic primary production. When they die, their fossilized shells accumulate into diatomite, a porous sedimentary rock that, when ground into powder, becomes diatomaceous earth. This material, often dismissed as a mundane garden additive or insecticide, is in reality a vast archive of ancient life—literally the 'necro dust' of billions of prehistoric organisms. The episode reveals how this fossilized silica acts as a mechanical pesticide: its razor-sharp, microscopic shards slice through insect exoskeletons while simultaneously absorbing lipids and causing lethal dehydration. The hosts explore the eerie, almost sci-fi horror of this process, likening it to a valley of thorns for insects. They also trace the ancient use of diatomaceous earth back to Neolithic China, possibly inspired by birds’ dust baths, which mechanically dislodge mites. The episode underscores how scale transforms danger: what is harmless to humans is a lethal trap to insects, revealing a hidden, violent world beneath the surface of everyday materials.