and others. The area is also referred to as Western Ranchi Plateau. It is believed to be composed of Deccan basalt lava. Ranchi Plateau The Ranchi Plateau is the largest part of the Chota Nagpur Plateau. The elevation of the plateau surface in this part is about and gradually slopes down towards south-east into the hilly and undulating region of Singhbhum (earlier the Singhbhum district or what is now the Kolhan division). The plateau is highly dissected. The Damodar River originates here and flows through a rift valley. To the north it is separated from the Hazaribagh plateau by the Damodar trough. To the west is a group of plateaus called pat. There are many waterfalls at the edges of the Ranchi plateau where rivers coming from over the plateau surface form waterfalls when they descend through the precipitous escarpments of the plateau and enter the area of significantly lower elevation. The North Karo River has formed the high Pheruaghaugh Falls at the southern margin of the Ranchi plateau. Such falls are called scarp falls. Hundru Falls (75 m) on the Subarnarekha River near Ranchi, Dassam Falls (39.62 m) on the Kanchi River, east of Ranchi, Sadni Falls (60 m) on the Sankh River (Ranchi plateau) are examples of scarp falls. Sometimes waterfalls of various dimensions are formed when tributary streams join the master stream from great heights forming hanging valleys. At Rajrappa (10 m), the Bhera River coming over from the Ranchi Plateau hangs above the Damodar River at its point of confluence with the latter. The Jonha Falls (25.9 m) is another example of this category of falls. The Ganga River hangs over its master stream, the Raru River (to the east of Ranchi city) and forms the said falls. Hazaribagh Plateau The Hazaribagh plateau is often subdivided into two parts – the higher plateau and the lower plateau. Here the higher plateau is referred to as Hazaribagh plateau and the lower plateau as Koderma plateau. The Hazaribagh plateau on which Hazaribagh town is built is about east by west and north by south with an average elevation of . The north-eastern and southern faces are mostly abrupt; but to the west it narrows and descends slowly in the neighbourhood of Simaria and Jabra where it curves to the south and connects with the Ranchi Plateau through Tori pargana. It is generally separated from the Ranchi plateau by