Lava coil

A lava coil is a spiral or scroll-shaped lava formation occurring when relatively low viscosity lava such as Pahoehoe solidifies along a slow-moving shear zone in the flow. The shear produces a Kelvin–Helmholtz instability that forms spiral-shaped patterns. Depending on the side of the flow the spiral is clockwise or anti-clockwise. They have been observed on flows near Kilauea on Hawai'i,^[1] in Kenya^[2] and possibly on Mars.^[3]

• Lava Coils on Earth and Mars
• 
  Surface of December 31, 1974 pahoehoe northeast of Pu‘u Koa ́e, Hawaii. Lava coil is 10 m diameter.
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  Spirals interpreted to be lava coils^[3] on the surface of a Martian lava lake in Cerberus Palus. Field of view is about 500 m.