What is the Difference Between AA and Pahoehoe?

The main difference between AA and Pahoehoe lava lies in their appearance, formation, and cooling process. Both AA and Pahoehoe lavas are basaltic in nature and originate from Hawaiian volcanoes. Here are the key differences between the two:

• Appearance: Pahoehoe lava has a smooth, billowy, or ropy surface, while AA lava has a rough, jagged, spiny, and generally clinkery surface. Pahoehoe lavas are characterized by smooth surfaces, while AA lavas are characterized by sharp, rough, and clinkery surfaces.
• Formation: AA lava forms when lava flows rapidly, while Pahoehoe lava forms when lava moves slowly. Pahoehoe lava flows are produced from a small amount of lava that moves slowly, while AA flows usually are associated with a large volume of lava that moves rapidly.
• Cooling Process: Pahoehoe lava cools slowly, while AA lava cools quickly. The difference in cooling rates is due to the varying flow rates and the release of gases. In the case of Pahoehoe lava, gases have not been able to escape the outer surface, creating a ropy and smooth surface. In contrast, AA lava moves fast, and gases escape from the upper surface, creating clinkers and a jagged outer structure.
• Viscosity and Fluidity: Pahoehoe lava is more fluid than AA lava. AA lava flows have higher viscosity and slightly higher temperatures.
• Flow Rate and Velocity: AA lavas have a high volume flow rate and high flow rate velocity, while Pahoehoe lavas have a low volume flow rate and low flow rate velocity.

In summary, the primary differences between AA and Pahoehoe lavas are their appearance, formation, cooling process, viscosity, and flow rate. AA lavas are characterized by their rough and clinkery surfaces, high flow rates, and faster cooling, while Pahoehoe lavas are characterized by their smooth and ropy surfaces, slow flow rates, and slower cooling.

Comparative Table: AA vs Pahoehoe

The main differences between pahoehoe and aa lava are their appearance, texture, and the conditions under which they form. Here is a summary of their differences:

Pahoehoe lava flows are smooth and undulating, forming close to the source of the eruption and on steep inclines where gravity aids flow. Aa lava, on the other hand, is rough, rubbly, and often sharp, forming further from the eruption or on flatter surfaces. Pahoehoe lavas have a lower viscosity and form at slightly higher temperatures, while aa lavas have a higher viscosity and form at slightly cooler temperatures. The two types of lavas can be produced by the same volcano and magma.