Question

how do most rock layers form?
when lava cools in the ocean
from layers of sediment building up over time
when rocks melt underground
from earthquakes shaking the ground

Explanation:

Most rock layers, especially sedimentary rock layers, form through the accumulation of sediments over time. Sediments like sand, silt, and clay are deposited by processes such as water flow, wind, or ice. As these sediments build up layer by layer, they are compacted and cemented together to form rock layers. Lava cooling forms igneous rocks (not most rock layers), rocks melting forms magma (not rock layers), and earthquakes shaking the ground can displace rock layers but not form them primarily.

Answer:

From layers of sediment building up over time