In a continental collision, a subducting tectonic plate pushes on the plate above it, making the rock fold, often to the point where thrust faults form, and a mountain chain rises. On the upper plate, the land between the mountains and the undeformed continent bends downward, forming a foreland basin. If the basin forms slowly, as in the northern Appalachians, it fills with shallow-water sediments. If it forms rapidly, as in the east side of the North American Cordillera, then sea water may rush in, and the first sedimentary deposits are deep water deposits. If the mountain slope is steep enough at the edge of the basin, it will shed material in rapidly moving sedimentary flows called turbidity currents, resulting in turbidite deposits. As the basin fills up, shallow-water sandstones and continental deposits form. Most of the resulting rocks have little deformation, but near the edge of the mountain chain they can be subject to folding and thrusting. After the basin fills up, continental sediments (molasse) are deposited on top of the flysch.