Correction to: Nature Geoscience https://doi.org/10.1038/s41561-019-0326-6, published online 19 March 2019.

In the version of this Article originally published, in the sentence “There are three identified boulders with long axes exceeding 40 m and more than 200 boulders larger than 10 m2”, the term “10 m2” should have been “10 m (ref. 2)”. This has now been corrected.