Pyroclastic Breccia Patterns 5 – Angular rock fragments embedded in a volcanic ash matrix from a pyroclastic flow in Cape Breton Island near Louisbourg Lighthouse, Nova Scotia, Canada. I’m not certain but the largest piece of rock shown in this image looks a bit like a volcanic bomb – these form when globs of molten lava are expelled from the vent of the volcano and solidify as they fly through the air before landing in the ash.