A maar landscape is a low flat crater landscape with no volcanic cone but only a wide flat crater. It is a type of volcano that forms during an eruption caused by the interaction between cold water and hot rising magma. This type of volcano is characterised by a wide crater that extends underground or cuts into the surrounding rock mass. The crater edge curves upward with a gentle slope. There are numerous maars in the Eifel area in Germany; many are filled with water and hence are called ‘mare’, which literally means ‘sea’. In studies of volcanoes, this type of structure is called a maar. There are maars in the Haikou, Zhanjiang and Huinan areas of China (Figs. 1 and 2).

Fig. 1
figure 131figure 131

Maar landscape in Shuangchi Ridge, Haikou

Fig. 2
figure 132figure 132

Maar landscape in Luojingpan, Haikou (the crater has become farmland)