These horizontal layers could be sedimentary rock (rock formed by the accumulation of mineral matter deposited by the action of water, wind, or glacial 
(These horizontal layers; could be; sedimentary rock) (rock; formed; by the accumulation of mineral matter) (the accumulation of mineral matter; deposited; by the action of water, wind, or glacial)
These horizontal layers rock the accumulation of mineral matter
could be formed deposited
sedimentary rock
by the accumulation of mineral matter
by the action of water, wind, or glacial