pāhoehoe flow on the coastal plain with pali in background. As the ...

A closer look at the pāhoehoe flow on the coastal plain with pali in background. As the flow spread across the ground, its surface cooled and developed a hardened crust. Continued addition of new lava into the interior of the flow eventually raised and broke through the rigid crust, allowing molten lava from the interior to escape through the new openings and spread forward. Note the rigid crust on top of the red, molten lava.