After being ejected out to the surface, the lava begins to coolsolidify. During cooling, many shrinkage centers are generated on the top of the lava according to the temperature of the environment at the time. When the temperature is lowcold, the distance between the shrinkage centers are denser, otherwise the distance between the shrinkage centers become larger. The joints of basalt extend downward from the two shrinkage centers to produce cracks, like mud cracks, which are columnar joints of basalt. During the crystallization process, the lava shrinkssplits into polygonal columns. Cylinders vary in shapes ranging from quadrilateral to octagonal forms, with pentagonshexagons being the most common. The joint direction is perpendicular to the distribution direction of lava flow temperature. The joints of the columnar body can help us determine howwhere the lava has erupted. The columnar body can be thickthin,the direction of the structure can be vertical, horizontal, inclinedfan-shaped. Among them, the vertical direction is mostly formed by the lava extruding out of the earth surface the horizontal direction may be formed by the intrusive rock mass,the inclinedfan-shaped directions can be formed by both intrusiveextrusive rock masses. The columnar joints of Qimei Northwest Bay are the most spectacular columnar landscapes in Penghu basalt. The specimens collected by this center are from Paisha Township’s Tongliang, Paishayu,Siyu’s Daguoye.