The Voi Mep massif of the Truong Son range, having the highest peak in the Quang Tri area (1739m), is composed of granite and granodiorite intrusive rocks in Ben Giang-Que Son complex. This massif is fairly isometric with characteristic landforms comprising: remnants of old pediment surfaces, mountain slopes and valleys with steep profiles. The massif area has a regular altitudinal differentiation manifested in the formation of two climatic belts: tropical humid climatic belt, subtropical humid climatic belt; two altitudinal soil belts: red yellow soil belt and red yellow humus soil belt; four altitudinal vegetation cover types: evergreen broadleaf.
