geosyncline
/ˌdʒioʊˈsɪnˌklaɪn/
noun
- A large, long, deep depression in the Earth's crust where thick layers of sediment accumulate, often leading to mountain formation.
- A geosyncline can take millions of years to fill with sediment.
- Geologists mapped the geosyncline to understand the region's geological history.
- The Appalachian Mountains were formed from an ancient geosyncline.