Yesterday, I transported two fun groups to the Hamakua Coast. One young lady asked me some questions about the distinction between the two lava types and why do they form so differently… She gave me the idea for this weeks blog 😀
When exiting the Ellison Onizuka Kona International Airport At Keahole, heading North, you’ll see amazing fields of black and brown lava rock. These rocks are the result of the two main types of lava flows; Pāhoehoe (pronounced ‘paw-hoey-hoey”) and A’a (pronounced “ah-ah”).
Both names are from the Hawai’ian language (they have no meaning other than the lava types) and adopted by the scientific community as the “official” names of these lava flows and their molten rock.
To me, Pāhoehoe looks like a pan of brownies that have stayed in the oven a little too long. With cracks and crevices atop of a smooth or “ropy” surface. A’a (pronounced “ah-ah”) looks like taco meat crumbles. Typically brown or reddish-brown in color, A’a is much rougher in comparison to Pāhoehoe.
Pahoehoe forms when lava flows more slowly. Under these circumstances, a well-developed skin can form which inhibits heat loss. When a tear in the skin does form, it is readily healed.
A’a forms when lava flows rapidly. When this happens, the heat escapes quickly resulting in an increase in viscosity. When the surface crust breaks by differential flow, the lava that is below is unable to move fast enough to seal the break. The crust then forms chunks.
It’s all about the flow dynamics that will determine the type of lava that will form. Think: slow-flowing lava= Pāhoehoe, and for quick-lava= A’a.
There is a third type of flow that takes place on the ocean floor. It’s called Pillow Lava due to the pillow like shape that forms from cooling off so quickly underwater.
If you catch a ride with me from the airport, ask me to point out the different lava rocks. Unfortunately, without scuba gear, I’ll be unable to show you the Pillow Lava:)