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![Rare small scale volcanic rock structure expn5934.jpg Rare small scale volcanic rock structure](/sites/default/files/styles/max_1300x1300/https/s3.amazonaws.com/s3-east-testmedia-noaa.woc.noaa.gov/dam/Photos/legacy/pl23_expn5934.jpg?itok=RK5bSi7o)
Description
Rare small scale volcanic rock structure. Although field identified as spongematerial, a look at expn5933 reveals this small structure to be part of thesubstrate. Perhaps formed by some form of small scale venting as gas escapedfrom underlying lava flow. (Image credit: NOAA Office of Ocean Exploration and Research, 2015 Hohonu Moana)