What type of lava is slow-moving and hardens to form rough chunks?

The type of lava that is slow-moving and hardens to form rough chunks is known as Aa. Aa lava is characterized by its jagged, blocky surface and tends to be thicker and more viscous than other types of lava. When it flows, its movement is quite sluggish, allowing it to cool and solidify into these rough, angular blocks. This is a result of the higher viscosity, which means it does not flow as easily and breaks apart during movement, creating the fragmented appearance typical of Aa flows.

In contrast, basalt is a general category of volcanic rock and does not specifically describe the texture or flow characteristics. Pahoehoe lava, on the other hand, is known for its smooth, rope-like surface and tends to flow more easily than Aa lava. Andesite is another type of volcanic rock, typically associated with intermediate compositions and can have varied flow characteristics. However, it generally does not refer to the specific rough texture that Aa lava exhibits.