1. Carbonation
   1. water falls through air
   2. absorbs carbon dioxide
   3. carbonic acid forms
   4. carbonic acid reacts with calcium carbonate
      1. forms calcium Bi carbonate
   5. calcium bicarbonate is dissolved
      1. removed in solution
   6. EG
      1. The Burren
      2. Dunmore Caves
2. What
   1. distinctive landforms
   2. limestone rock
3. Where
   1. in Ireland
      1. Burren
      2. Marble Arch in Fermanagh
   2. International
      1. Karst region
      2. Slovenia
4. how
   1. Rainwater absorbs carbon dioxide
   2. turns calcium carbonate in limestone
      1. bicarbonate
      2. soluble
   3. Dissolves limestone.
5. Main Topic 4