Northwestern thorn scrub forests are found. Himalayan subtropical pine forests dominate the lower elevation Himalayan foothills. The Western Himalayan broadleaf forests are found at elevations of . At higher altitudes, Western Himalayan subalpine conifer forests are found. Above these, Western and Northwestern Himalayan alpine shrub and meadows are the only vegetation found at elevations between . Beyond lie permanent ice and snow. The state has five national parks: the Great Himalayan National Park (a world heritage site), Pin Valley National Park, Inderkilla National Park, Khirganga National Park and Simbalbara National Park. Geographical characteristics Elevation ranges from to over above sea level. The region extends from the Shivalik range of mountains. There is a noticeable increase in elevation from west to east and from south (Shiwalik]) to the north (outer Himalayas). At 6816 m Reo Purgyil is the highest mountain peak in the state of Himachal Pradesh. The four general physiographic divisions from south to north are: The outer Himalayas (Shivaliks): Shivaliks range consists of lower hills (600 m above sea level). The hills of the region are composed of highly unconsolidated deposits which results in high rates of erosion and deforestation. The lesser Himalayas (central zone): The lesser Himalayas have a gradual elevation towards the Dhauladhar and the Pir Panjal ranges. The rise is more rapid in the Shimla hills, to the south of which is the high peak of Churdhar (3647 m). North of the river Sutlej, the rise is steady. The Kangra valley is a longitudinal trough which is at the foot of the Dhauladhar range. Dhauladhar (which means the 'White Peak') has a mean elevation of nearly 4,550 m. It has a rapid rise of 3,600 m above the Kangra valley. The largest of the lesser Himalayan ranges, the Pir Panjal, branches off from the Greater Himalayan range near the bank of the Sutlej. A number of glaciers exist and several passes lie across the Pir Panjal. The Rohtang Pass (3,978 m) is one of these. The Great Himalayas (northern zone): The Great Himalayan range (5,000 to 6,000 metres) runs along the eastern boundary and is slashed across by the Sutlej. Some of the famous passes in this range are Kangla (5,248 m), Bara Lacha (4,512 m), Parang (5,548 m), Cheni Pass Churah Pangi (4,400m), and Pin Parvati (4,802 m). Zanskar range (Shilla Peak (6,132 m) in kinnaur, Pangi in Chamba): The Zanskar Range, the easternmost range,