<p>According to the USGS, "A breadcrust bomb is a volcanic bomb with a cracked and checkered surface, sometimes resembling the surface of a loaf of bread. The cracks develop when the outer surface of a partially molten lava fragment cools to form a brittle surface and then subsequently cracks as the hot interior expands due to the continued growth of gas bubbles."
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This bomb has been broken by frost wedging. NPS photo by M. Fitz.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/99350217@N03">Katmai National Park and Preserve</a>
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/katmainps/13542972664/">Breadcrust bomb near Novarupta, Valley of Ten Thousand Smokes, Memorial Day Weekend 2010 079</a>