sentence2_structure: sediments<>settle<>out of water$$$they<>form<>horizontal layers<>When sediments settle out of water
sentence1: Water injected into unconfined sand forms a stationary dome, and if there are confining layers then water spreads out horizontally.
sentence2: When sediments settle out of water, they form horizontal layers.
question: When sediments settle out of water, what do they form?