When icebergs break apart owing to increased temperatures, they often release part of their underwater structure and also provide some insight into their inner parts. These often are conspicious cavities the walls of which very often have a wafer-like structure.
<a href="//commons.wikimedia.org/wiki/User:AWeith" title="User:AWeith">Andreas Weith</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>