Instead , rain water percolates through the rock , and may spend 25 years underground before emerging 50 kilometres away at Mzima .
The Chyulu range is composed of volcanic lava rock and ash , which is too porous to allow rivers to flow .
Rain water percolates through the rock , and may spend 25 years underground before emerging 50 kilometres away at Mzima .
The Chyulu range is composed of volcanic lava rock and ash , which is too porous to allow rivers to flow .