(a)Mode of formation of stacks - formed near a coast-formed by wave erosion - presence of headland wave erosion attacks headland at both sides - cracks or lines of weakness develop on both sides of the 6 headland - cracks widen - hydraulic action wave abrasion - caves are formed from the cracks on both side of headland - further erosion causes adjacent caves to join - an arch is formed - roof of arch collapses - stack is formed - further erosion reduces stack to a stump examples include the Old Man of Hoy and the Needles of England, Axim Stack in Ghana, Nkontompo stack in Ghana.
(b) Mode of formation of fold mountain: - formed from large scale earth movement - horizontal movement or crustal blocks - formed by compression forces within the earths crust - the forces cause stress within the crust - presence of large depression called geosynclines - depression or geosynclines caused by down wraping of the crust - materials eroded from continental blocks are deposited in the depressions - sedimentary rocks are formed weight of sediments causes further subsidence of the geosynclines-of the sediments causes adjacent continental blocks/tectonic plates to move towards each other - compression of the sediments leads to the warping (up folding and down folding) of deposits upfolds are called anticlines -downfolds are called synclines - upfolds become crests of fold mountains - further narrow e aepression causes more intense folding ttat form fold mountain examples include Rocky, Andes, Mt. Alps, Atlas Mt., etc.