The US Geological Survey's Tina Neal said the lone volcanic fissure that was still active last week had dwindled from a fountain of molten rock to a bubbling pond of lava, no longer spilling out of the cone surrounding it.
Levels of sulfur dioxide gas vented from the fissure, located on the lower east flank of Kilauea, had also dropped dramatically, she said.
The subdued activity there coincided with another major collapse in the outer wall of the summit crater last week.
Scientists would be surprised if the summit crater produced any new major eruptions in the near future, Dr Neal said.
At the height of Kilauea's current eruption, which began on 3 May, a total of two dozen fissures opened in the ground at the foot of the volcano in an area scientists call the lower east rift zone.
But only one vent, dubbed Fissure 8, was still active last week.