If a stalagmite and stalactite become long enough and meet, they will form a rocky column. Columns are also created when a stalactite grows down to touch the cave floor.
As compound cave formations, they include among their ranks the tallest free-standing speleothems in the world. (Certain flowstone falls–sheets of calcite lining vertical shafts–are undoubtedly taller, but rarely measured). The towering specimens of the upper left photo, from Ogle Cave in Carlsbad Cavern National Park, New Mexico, USA, are indeed impressive. These, however, are only about half as high as the 61-meter tall column in Tham Sao Hin, a cave in Thailand.
Picture Credit : Google