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Types of Lava

There are three types of basaltic lava flows: aa, pillow, and pahoehoe

The fluid basalt lava flows form flat sheet-like bodies (explained below) versus the rather blocky masses or rock formed by more viscous rhyolite lava flows.

Aa lava

  • from Hawaiian meaning "stony rough lava"
  • very rough, sharp, and jagged surface of broken lava blocks called clinkers created as lava cools and solidifies
  • emitted from vents at high rates/speed in fountaining effect
  • typically erupts at 1000 to 1100 °C
  • typically thick flows up to 10 meters
  • makes hiking difficult and slow
  • ex: Sunset Crater - Lava Flow Trail

Pahoehoe lava

  • from Hawaiian meaning "smooth, unbroken lava"
  • smooth, undulating and ropy surface
  • smaller volumes/flows or lobes that break out from cooled crust with strange shapes
  • typically flows at 1100 to 1200 °C
  • typically under a meter thick

Pillow lava

  • most abundant type erupting at mid-ocean ridges
  • typically forming pillow like flows emerging from underwater volcanic vents