Flexi Says: In general, plate tectonic processes build up mountains while weathering and erosion wear them down. However, some mechanics of tectonic plates can result in lowering the height of mountains. In divergent areas where plates are pulling apart, the tension on surrounding land can cause thinning which lowers the height of the land overall, and fracturing which can create basin and range topography. Also, in convergent areas where mountains form, the heat caused by the collision forces results in rock decreasing in density and increasing in volume. As the tectonic environment changes and the rock cools it contracts and sinks slightly, lowering the height of the mountains.