“shale rock”造句，怎麼用shale rock造句

Soil in hilly regions in the middle of Sichuan Province is mainly a type of purple soil which has been developed from the purple shale rock.

Like America, Europe has vast beds of shale rock, in which innumerable bubbles of natural gas are trapped.

Then came a technological breakthrough in the United State, where firms found a way to free gas previously trapped in shale rocks.