A lava fragment that is ejected while viscous (partially
molten) and larger than 64 mm (2.6 in) in diameter. Many volcanic bombs
acquire rounded aerodynamic shapes during their travel through the air.
Volcanic bombs include breadcrust bombs, ribbon bombs, spindle bombs (with
twisted ends), spheroidal bombs, and "cow-dung" bombs.
| Basaltic lava bombs erupted
by Mauna Kea Volcano, Hawai'i.
Credit: J. P. Lockwood / U.S. Geological Survey
AND PLANETARY SCIENCE
Source: U.S. Geological Survey