syncline
nounUK /ˈsɪŋ.klaɪn/
US /ˈsɪn.klaɪn/
A syncline is a fold in the ground that dips down in the middle like a big smile.
The hikers walked along the bottom of the syncline where the rocks curved downward.
OTHER MEANINGS
2. A downward-arching fold in rock layers whose youngest beds lie in the center.
Geologists mapped the syncline by noting that the youngest rock layers were at its core.
3. Any trough-shaped structure or depression resembling a geological fold.
The valley formed a gentle syncline that collected rainwater.
4. In structural geology, the line connecting the lowest points of a folded surface.
The syncline axis ran east to west across the ridge.