What is the cause?

[guohua]

Ok My Friends, here is another Volcano.

Activity from Alaska volcano triggers aviation warnings after spewing ash, lava
The Shishaldin Volcano is currently listed at a Code Orange alert level.

I think the last time this one was active was in the 1700's

Activity from one of Alaska's 80 volcanoes triggered aviation warnings after it began to spew ash and lava over the weekend.

At some points, the ash reached about 28,000 feet, officials said. Trace amounts of the ash landed on False Pass, about 23 miles east of the volcano, the Anchorage Daily News reported.

Shishaldin is among the most active volcanoes in the area, with about 24 confirmed eruptions have occurred since 1775, according to the local newspaper.
Source