Steamboat geyser erupts

For the first time in nine years the world's tallest active geyser, the Steamboat geyser, has erupted in Yellowstone National Park, home to the famous Old Faithful, known for going off regularly.

Steamboat's eruption sent up a huge vapour plume 150m and was the geyser's first since 1991.

Yellowstone has around 250 active geysers constantly gurgling and spraying.

The schedule for the most famous "Old Faithful" can be calculated to within 10 minutes, but not so with the Steamboat geyser. Its eruptions can vary from three to 50 years.