Sapropels are dark, organic-rich sedimentary rocks found at the bottom of some bodies of water.
Sapropels are important for scientists who study the history of the Earth and the environment.
Examples:
The scientists found sapropels at the bottom of the lake.
The sapropels are very old and full of plants.
We can learn a lot from the sapropels about the past.
The fish don't like to swim near the sapropels.
The sapropels are like a time machine, showing us what the Earth was like long ago.
The sapropels are like a secret book that tells us stories about the Earth.