what are the 6 types of mechanical weathering?
['Frost Wedging or Freeze-Thaw. ••• Water expands by 9 percent when it freezes into ice. ... ', 'Crystal Formation or Salt Wedging. ••• Crystal formation cracks rock in a similar way. ... ', 'Unloading and Exfoliation. ••• ... ', 'Thermal Expansion and Contraction. ••• ... ', 'Rock Abrasion. ••• ... ', 'Gravitational Impact. •••']