Technique: How to Cross a Moraine

Learn how to find a safe route through glacial rubble, crossing a moraine with nothing more than boots and trekking poles.

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Most glacier travel requires expert crevasse-rescue and self-arrest skills. Not so on moraines—piles of rock and dirt that get pushed ahead of the glacier or that fall onto its surface from the mountainsides—collapsing snow bridges and, thus, exposing crevasses. So any hiker equipped with sturdy shoes, a keen eye, and trekking poles for balance can access these moonscapes.

Numerous types of moraines exist, but four of the primary kinds are:

>> Terminal These form as the glacier deposits rock piles at its toe.

>> Lateral The glacier pushes debris along its sides, creating long ridges.

>> Medial When two glaciers merge, the lateral moraines get squeezed together in the middle, forming rocky ridges along the suture line.

>> Supraglacial These fields of tumbled-down debris on the glacier’s surface, often several feet thick, cover the ice and reveal crevasses.

Most of this terrain is rugged, with crumbling slopes hundreds of feet high and rocks that range from tiny pebbles to house-size boulders. But other areas are undulating and smooth (more dirt than Jenga blocks). During backcountry travel, you might need to cross a moraine to reach another valley, or you may simply want to explore it. Here’s how:

>> Get a good view. Gain a high point and search for a passable route through the rubble. Look for ridgelines or flat, wide corridors, which are more stable. Don’t plot routes below steep, rockfall-prone slopes.

>> Take a photo from that vantage, so you can consult it along the way. Once you’re inside a moraine maze, knowing your location is tough.

>> Keep crampons ready. Supraglacial moraines often have icy patches.

>> Never place your feet below rocks big enough to crush your foot. Since the ice continually melts and shifts, even huge boulders can be loose.

>> Avoid steep slopes where loose rocks (and you) might slide. Unavoidable? Then watch for rockfall: Spread out or zigzag, collecting each member at the end of each switchback, so no one is above anyone else.

>> Beware ultra-slick, mud-covered ice. Test dirt patches with a pole first.

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