A Tertiary normal faulting system gave rise to the coastal ranges of Rio de Janeiro where Precambrian gneiss and granite rocks prevail. Geological structures favor the in situ origin of rounded boulders and blocs. Conspicuous morphological features are given by round-shaped rocky peaks, called "sugar loaf", and long-steep rock escarpments (>50°) operate as water recharge zones. Block-rich slope deposits (talus and colluvium) are relatively thicker at the foot of rock-escarpments or along gentle inclined valley bottoms.

In the Tijuca massif a late secondary Atlantic rainforest yet prevail despite the strong urban pressure in the surrounding area; however forest degradation is accelerated onto steep slopes due to urban interferences. Two extreme rainfall events were recorded in the last 30 years in the Upper Tijuca massif (Tijuca National Park): one in February 1988 reached 260mm in the critical day; another in February 1996 when rainfall intensity attained 380 mm in less than 24 hours.

The 1988 event (Guidicini-Iwasa coeff. of type B) led to sparse landslides in the steep slopes of the National Park and surrounds, being more concentrated along the road cuts. In the 1996 event (Guidicini-Iwasa coeff. of type A, or extreme landslide hazard), several landslides spread simultaneously onto the steeper western slopes of Papagaio peak, being relatively sparser in the eastern slopes which drain toward the National Park. Initiation was probably related to mass impact or suddenly increase of pore-pressure; debris flows predominated and few shallow failures occurred. The downward propagation was strongly influenced by topography and forest degradation. The eastern-landslides occurred within the National Park and did not propagated far away apart from their initial places: coarse debris load (blocs, soil and trees) remained stored in minor hanging plateaus. The longer and steeper western slopes were largely affected by landslides and extensive rock debris avalanches (>4 km length) reached the adjacent baixada of Jacarepaguá. Avalanches led to bedrock incision, leaving behind deeper and wider channels.