Ice-marginal lava flow

The barrier is left behind as the ice retreats, leaving a thick lava front, which is in the form of a large, steep and unstable cliff face.

The vertical slabs of lava that make up The Barrier occasionally collapse to form massive rock avalanches that travel down the valley toward local residences.

The biggest threat posed by The Barrier is a complete collapse of the lava dam due to volcanic activity or erosion.

[3] A second example of ice-marginal lava flows can be found at Hoodoo Mountain, a flat-topped stratovolcano in British Columbia, Canada.

Mount Ruapehu, the tallest mountain on the North Island of New Zealand, is a massive stratovolcano that has also produced ice-marginal lava flows.