The unique black and pink landforms of the ahaggar were formed by

volcanoes

Explanation:

The ahaggard mountains are a highland region of the central Sahara and are found along the tropics of the cancer are approx  550,000 km square. Having an elevation of about 2,908 meters.  Consists of an area of a large rocky desert the Mount Tahat is the highest peak. These mountains range typically experiences hot summer and cold winter being composed of the metamorphic rocks they have volcanic activity. Many of the volcanoes are extinct and erosional activity takes on a daily basis and this leaves more resistant rocks. The Ahaggar massif, Algeria is one of the major attractions due to the scenic landscape created by these relic mountains.