What is this

What is this

Observation - What is this - UK and Ireland. Description: We found this on the shore, where it had been washed from the cliff. It was quite hard. It had started forming in the ground, before being washed out. Can anyone explain what is happening here?

We found this on the shore, where it had been washed from the cliff. It was quite hard. It had started forming in the ground, before being washed out. Can anyone explain what is happening here?