Giant's Causeway cases the horizontal fracture has resulted in a bottom face that is convex while the upper face of the lower segment is concave, producing what are called "ball and socket" joints. The size of the columns is primarily determined by the speed at which lava from a volcanic eruption cools. The extensive fracture network produced the distinctive columns seen today. The basalts were originally part of a great volcanic plateau called the Thulean Plateau which formed during the Paleocene. According to legend, the columns are the remains of a causeway built by a giant. The story goes that the Irish
François Leguat Giant Tortoise and Cave Reserve François Leguat Giant Tortoise and Cave Reserve François Leguat Giant Tortoise and Cave Reserve ("Francois Leguat Reserve") is a park and nature reserve on the island of Rodrigues, dedicated to protecting the fauna and flora of the island. The reserve first opened in August 2007, part of the same project as La Vanille Reserve in Mauritius. It is named after the 18th century Huguenot settler François Leguat, who recorded much of the island's natural flora and fauna before it went extinct. The reserve includes a museum, several enducation centres and information areas, and a restaurant. Rodrigues was once home to