boulder clay

American  

noun

Geology.

1. a glacial deposit consisting chiefly of unstratified clay with embedded boulders.

---

boulder clay British  

noun

1. an unstratified glacial deposit consisting of fine clay, boulders, and pebbles See also till 4

---

Etymology

Origin of boulder clay

First recorded in 1855–60

Example Sentences

Happisburgh, home to about 1,100 people, is so susceptible to erosion because the cliffs are made from boulder clay which slumps when wet.

From BBC • Dec. 30, 2022

And this must have taken place before the glacial period, because the glacial boulder clay lies upon the Kimeridge clay, which normally underlies the chalk. 

From Records of Woodhall Spa and Neighbourhood Historical, Anecdotal, Physiographical, and Archaeological, with Other Matter by Walter, James Conway

It is not clear, but black with mud, called boulder clay, or till, made of ground rock, and mixed with fragments of all shapes and sizes.

From Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place by Rogers, Julia Ellen

This boulder clay covers almost all the low ground north of the Thames Basin, its southern margin fading away into washed sands and gravels.

From Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 4 "England" to "English Finance" by Various

Much boulder clay is of a bluish-grey colour where unexposed, but it becomes brown upon being weathered.

From Encyclopaedia Britannica, 11th Edition, Volume 4, Slice 3 "Borgia, Lucrezia" to "Bradford, John" by Various