earthberg

A mass suspended or floating in water, similar to an iceberg, but consisting of earth (dirt, soil, etc.).

The landscape of the Elemental Chaos is broken up by rivers of lightning, seas of fire, floating earthbergs, ice mountains, and other fantastic terrain features.

Marrec mentally labeled the floating islands 'earthbergs.' He saw a few perfect cubes, each face a mirror, tumbling through the darkness.

A mountain or large mound of earth.

Unsurprising, given that he'd spent most of his life in the Well, sheltered by the very earth-berg he now rose beside, hoisted on creaking cables.