The surface of lava flow will be cooled down and solidified during the process. The part of lava surface will undergo pushing, twisting and rotating to different degrees, thus forming ropy or twisting surface after cooling. Generally, the arcuate protruding direction of ropy surface points to the flowing direction of lava. The pahoehoe has low viscosity and is easy to flow. Its flow velocity ranges between 0-30 km/h. The surface of pahoehoe lava have various forms, but the ropy, wavy and smooth pahoehoe lava are very common in Jingpohu area.
The ropy and the wavy lava enjoy the following features:
1. The lava surface has the wavy rise or bend, and the lava with small waves of surface are usually called ropy lava.
2. The lava flow is with usually small thickness of only 1-5 m.
3. The upper and lower parts of lava flow lack fragments and occasionally thin “fragment layer” can be observed in the lower area. Usually vesicles develop in the upper and lower parts.
4. Large degassing pipes or fumaroles can be formed.
5. The lava transitions to aa lava along the direction or edge.