AA Lava Landscape

This is a type of blocky lava landform. Blocky lava is different from ropy lava because its surface is blocky in shape. In the local Hawaiian language, it is called ‘Ah’; hence, aa has been used in the literature to represent this blocky lava. The surfaces of aa lava flows often contain porous or dense fragments, and small fragments of the same composition fill the gaps between the large fragments. This lava sometimes transforms into ‘secondary lava’ due to its heat. The central portion of the lava is often a monolithic lump. The bottom of the lava can either be composed of fragments accumulated from the broken shell of the lower part of the lava flow or debris accumulated from the peeled off or disintegrated surface of the lava flow as a result of movement in a rolling wave pattern. The lava blocks in Wudalianchi are a typical example (Fig. 1).

Fig. 1

Aa lava landscape in Longmen Shizhai, Wudalianchi