Clay in the hole

I found this marl pit in a field while on a walk. Red marl is a layer of clayey soil beneath the surface clay, and it’s easy to get at in north Staffordshire, which is full of the stuff. It’s traditionally good for fertiliser, and for red-clay pots.
Someone here decided it was too accessible to waste.

Across the rest of the area, there are 'marl holes' big enough to play a football game in, but they soon fill with rainwater. In the old days, kids used to swim in such marlpits, but most are filled in now.