Question

Which lava flows are more viscous, pahoehoe lavas, or a'a' lavas?

a) Pahoehoe are more viscous
b) a'a' are more viscous

Answer 1

A'a' lavas are more viscous than pahoehoe lavas, leading to slower flow, rough surfaces, and the ability to overtop and 'burrow under' barriers as experienced during the 1960 Kapoho Eruption in Hawaii.

Step-by-step explanation:

A'a' lavas are more viscous compared to pahoehoe lavas. Viscosity in lavas is determined by factors such as temperature, chemical composition, and crystal content. Pahoehoe lava flows are typically less viscous, characterized by smooth, rope-like surfaces and are usually faster flowing due to their lower viscosity.

On the other hand, a'a' lava flows are much more viscous, forming rough, jagged, and clinkery surfaces.

They flow more slowly and cool into hard, crumbly rock with sharp edges. The high viscosity of a'a' lavas can also lead to a thicker, more resistant flow which can overtop and even 'burrow under' barriers, as was the case during the 1960 Kapoho Eruption in Hawaii.