Mashan is located about 7 kilometers west of Jimo City in Qingdao. It consists of four connected hillocks and is shaped like a saddle, so it is also called "Ma'an Mountain". The highest peak is about 211 meters above sea level. Andesite porphyrite is abundant on the mountain. Most of it is grayish-green or grayish-brown and was formed by magma gushing out of the earth's surface and condensing about 100 million years ago. In the southwest part of the mountain, there are square columnar joints.

The cross-sectional diameter of each column is about 1 meter, and the height is about 30 meters or more. They stand straight and tall and are closely arranged, just like a dense forest, presenting a magnificent sight. Therefore, it is named "Mashan Stone Forest". Columnar joint stone forests usually develop in basalt and generally take the shape of hexagonal or pentagonal columns. However, the Mashan Stone Forest develops in andesite and is square-shaped, which is relatively rare in geology.