What are the differences between basaltic and andesitic lava?

The key word that should be used when describing different lava types is viscous, which essentially means how thick the lava is, with a high viscosity describing a very thick, slow-moving lava. Andesitic lava is an example of a high viscosity lava whereas balastic lava has a low viscosity, so is more runny. High silica content in the andesitic lava contributes to causing this high viscosity and low silica content in the basaltic lava means it is of a lower viscosity. Both lavas are formed at different plate boundaries which is why they have different silica contents: the basaltic lava forms from the hot mantle material at constructive plate boundaries and hotspots whereas the andesitic lava forms at destructive plate boundaries from melting crust.