The world’s largest active geyser has erupted for the third time in less than six weeks.
Steamboat Geyser, in Yellowstone National Park, erupted at around 6.30am local time on Friday morning, geologists said.
The eruption is the latest event in a rare period of activity at the geyser this year, following similar water discharges on March 15 and April 19 this year.
Before this year, Steamboat had not erupted since September 2014.
The US Geological Survey said all events so far in 2018 had been smaller than recent major activity observed in 2013 and 2014.
Three @YellowstoneNPS #SteamboatGeyser water eruptions in 6 weeks!
Mar 15, Apr 19 & Apr 27. @UUSS_Quake_Info seismic data indicate eruption starting at 6:30 a.m. local time. All 2018 events have smaller signal than major water eruptions in 2013 and 2014. pic.twitter.com/rynJG4eppd
— USGS Volcanoes🌋 (@USGSVolcanoes) 27 April 2018
"Like most geysers, eruptions of Steamboat can't be predicted, they may be days or decades apart," Yellowstone said in a tweet.
Steamboat, located in the Norris Geyser Basin, can shoot a column of water up to 115 metres (380 feet) into the air, making it the world’s tallest active geyser.
Scientists have only ever recorded more powerful eruptions at the Waimangu Geyser in New Zealand, which has now been extinct for more than a century.
The geyser is around three times taller than Old Faithful, Yellowstone’s most famous geyser known for erupting at intervals of between 45 and 125 minutes.
The extensive geothermal activity at the park is caused by a magma chamber more than 50 miles (80km) long and 12 miles (20km) wide beneath the earth’s surface.
The event is thought to have been 2,500 times larger than the Mount St Helens eruption in 1980, the most recent major volcanic activity in the mainland US.