A GEOLOGICAL phenomenon which causes the ground to suddenlyopen up was the most likely inspiration for the subterreanean world ofAlice in Wonderland.

Lewis Carroll grew up in an area of Yorkshire famous forits dramatic subsidence and would have drawn on his own experience in describingthe rabbit -hole down which Alice made her famous journey.

Tony Cooper, principal geologist at the British GeologicalSurvey, has established convincing links between the gypsum-rich area aroundRipon, north Yorkshire, where holes in the ground frequently and suddenlyappear, and the children's fairytale. Gypsum is a highly soluble rock andis dissolved under the Ripon area at a rate of up to a foot a year.

Dr Cooper said a house near Ripon, called Ure Lodge, suffereddramatic subsidence in 1834 which left a hole 20 metres (64 feet) deepand 11 metres (35 feet) wide, and the young Dodgson would have almost certainlyvisited the scene. He also knew of a system of holes called "Hell's kettles",which were described by locals as bottomless pits.

"Lewis Carroll's father was Canon Dodgson of Ripon. Acontemporary of his, Canon Badcock lived in Ure Lodge, and was the fatherof Mary on whose photograph Alice in Wonderland's illustration was based,"Dr Cooper told the science festival.