Question: what is the difference between aa lava?
Answer: The surface of aʻā lava is sharp, rough, and 'clinkery', while Pāhoehoe lava surfaces have more smooth, billowy, or ropy crust, Pāhoehoe flows typically can change into ʻaʻā flows depending on the speed of the flow and the amount of gas present in the flowing lava, while the opposite (aʻā to pāhoehoe) is much rarer.