Why do some falls produce thousands of stones?
When a large meteoroid breaks apart in the atmosphere, it can shower thousands of fragments over a strewn field, as at Pultusk in 1868 and Holbrook in 1912.
Some meteorite falls deliver just one stone, while others scatter thousands. The difference comes from the meteoroid's size, strength and how it breaks up.
Fragmentation. As a meteoroid descends, pressure from the air builds on its front. When the pressure exceeds its strength, it breaks apart. Stony meteoroids are often riddled with cracks from earlier collisions in space, so they can break repeatedly, cascading into many fragments. Each fragment continues falling on its own path.
Famous showers of stones. - Pultusk, Poland, 30 January 1868: an estimated tens of thousands of stones, many of them small, often called Pultusk peas. It is one of the largest showers of stones known. - Holbrook, Arizona, 19 July 1912: an estimated 14,000 or more stones, mostly small, fell near the town of Holbrook. - L'Aigle, France, 1803: two to three thousand stones, which helped convince scientists that meteorites come from space. - Sikhote-Alin, Russia, 1947: an iron meteoroid that broke up and scattered many tonnes of fragments. - Chelyabinsk, Russia, 2013: thousands of fragments recovered, mostly small.
Strewn fields. The fragments land in an elongated area, usually with smaller pieces at one end and larger ones at the other, because air resistance slows small pieces more.
Value for science. Large showers provide abundant material for research and for collectors. They also help scientists understand how meteoroids break up, which matters for estimating the effects of larger impacts.