Why do lightning scars create fulgurites in sand?

A lightning strike can carry tens of thousands of amperes and heat the air to around 30,000 °C, far hotter than the surface of the Sun. When the discharge hits sandy ground, the intense heat melts silica-rich grains almost instantly. The melted material can fuse into branching, glassy tubes called fulgurites that preserve the path of the strike. They are found in deserts, beaches, and other sandy places after storms. Because each one forms from a single energetic event, fulgurites are natural records of lightning.