河北省张家口市以北的坝上地带广泛分布着玄武岩,面积约1700平方公里.根据地名,命名为汉诺坝玄武岩. 汉诺坝玄武岩最奇特之处在于节理面上有板痕条纹,以东西方向最明显,厚度几乎相等,为10厘米左右.石柱上的板痕条纹面稍有凹凸,与另一相邻柱面互为对应,好似浇铸模压的部件,形状奇特.板痕与柱体相互垂直,随柱体微向东斜(此乃新构造作用所致),如照片. Basalt is widely distributed in the Bashang area north of Zhangjiakou City, Hebei Province, covering an area of ​​1,700 km2. According to the place name, it is named as Hannuoba Basalt. The most peculiar thing about Hannuoba basalts is that there are slat stripes on the joint surfaces, The direction of the most obvious, the thickness is almost equal to about 10 centimeters.Plate marks on the stone column stripe slightly convex surface, and the other adjacent cylinder corresponding to each other, like casting molded parts, strange shape. Vertical, with the micro-Dongzhuan column (this is the result of neotectonics), such as photos.