They're generally circular and have steep walls . . One of the bulges being studied measures 100 feet wide by as many feet tall. The hot water can no longer vent. There has to be some place for that pressure to express itself. We're seeing the lake floor sediments getting pushed up, bulged up by pockets of gas that we're interpreting to be probably full of steam.
Deposits can have rock fragments that measure one to two meters in diameter.
These things get blown out and they have to fall back down. If the Matterhorn doesn't eventually blow up, it could collapse, says the USGS geologist. Morgan says a team of geologists are trying to determine whether these bulges are active, as well as whether they emit gases. In addition, the team is trying to determine whether the gases change over time. Most recently, long rows of spires have been discovered at the bottom of Yellowstone Lake in the Bridge Bay area.