In volcanology, ejecta consists of particles that came out of a volcanic vent, traveled though the air or under water, and fell back on the ground surface or on the ocean floor. Ejecta can consist of

1. juvenile particles - (fragmented magma and free crystals)
2. cognate or accessory particles - older volcanic rocks from the same volcano
3. accidental particles - derived from the volcanic basement.

In planetary geology, ejecta can also refer to the debris that is ejected during the formation of an impact crater.