The soils of the Altiplano, mainly clays, sands, and gravels—are dry and loosely consolidated; slopes that are exposed to strong winds or storm water are severely eroded. Soils to the south of the plateau are highly saline, but in the north rich topsoils border Lake Titicaca. In the Yungas the soils on the steep valley sides erode rapidly wherever forest is cleared and the slopes are not carefully terraced. The wider basins in the Valles region, particularly around Cochabamba, contain deeper, more fertile soils that respond well to irrigation. In the Oriente, topsoil quality varies, but there are large fertile expanses in Santa Cruz, where soybeans, cotton, and corn (maize) are grown.