1. Plural of eugeosyncline; elongated, subsiding troughs in the Earth's crust that accumulate thick sequences of sedimentary and volcanic rocks, typically located along continental margins.
Usage: geology; technical; largely historical term; replaced by modern plate tectonics terminology

Examples

• Eugeosynclines were thought to be the primary sites of mountain building in early geological theory.
• The concept of eugeosynclines helped geologists understand sediment accumulation patterns before plate tectonics.
• Ancient eugeosynclines along the Pacific coast deposited thousands of meters of rock material.
• Geologists mapped eugeosynclines to predict where mineral deposits might be found.
• The theory of eugeosynclines has been largely superseded by modern understanding of plate boundaries.