NEW : National Weather Service issues an advisory for areas around the volcanoes . An observatory reports ash plumes 20,000 feet above sea level over the Pavlof Volcano . The volcano is located in a remote area about 100 miles southeast of Reykjavik. An expert notes volcanic eruptions over Alaska can seriously affect air travel .
NEW : National Weather Service issues an advisory for areas around the volcanoes . An observatory reports ash plumes 20,000 feet above sea level over the Pavlof Volcano . That and another Alaska volcano remain on second highest alert status . An expert notes volcanic eruptions over Alaska can seriously affect air travel .