VANCOUVER, Wash. -- The eruption of Mount St. Helens that began two years ago is slowing down, a U.S. Geological Survey scientist said on Friday, but experts have no estimate of when the current eruption will end.

Video: Time-Lapse Of Dome’s Growth
Video: Time-Lapse Of Fin Growth
Video: Thermal Imaging Of Rock Avalanche

Cynthia Gardner said if the eruption continues at the current rate the mountain would rebuild itself in 80 to 120 years.

Scientists reviewed the activity Friday at a briefing at the Cascades Volcano Observatory in Vancouver.

The mountain began quaking in September of 2004 and steam and ash signaled the beginning of the latest eruption on Oct. 1, 2004. Hot lava was seen in the crater 10 days later.

With a lot of little quakes and a few steam bursts along the way, a lava dome has been growing in the crater. Gardner said there have been seven spines that arose and crumbled.

Measurements in August show the lava dome was 3,313 feet long, 1,673 feet wide and just 4 feet below the rim of the crater, which is 7,776.

There have been no explosive events in the past year.

Beginning Saturday, the current alert level will be called a "watch."

"It's unlikely that in the near future we'll see any change in the eruptive style," Gardner said.

In July, the U.S. Forest Service reopened a hiking trail to the summit and started allowing hikers back to the rim of Mount St. Helens.

The volcano's big blast in 1980 blew the top off the mountain killed 57 people.