What are these volcanic rocks "recording" when they solidify?

Definition: Volcanic bombs are lava fragments that were ejected while viscous (partially molten), and blocks are solid rock fragments; both are larger than 64 mm in diameter and are ejected during an explosive eruption.

Hope this helps :D

i think it is a system for harvesting crops more easily

offline recommendation systems option b

because recommendation systems produce a list of two ways

1. through collaborative filtering

or

2. through content-based filtering