Two Alaskan volcanoes had lava flowing down their sides yesterday causing authorities to put in place the second highest alert levels for both of them.

The pair of volcanoes, named Pavlof and Cleveland, are found in the southwestern region of the state, in the Aleutian Island range.

According to CNN, authorities put the volcanoes on alert because “sudden explosions…are possible with little or no warning.”

Heightened seismic and “eruptive” activity have led the Alaska Volcano Observatory to issue a watch of the two volcanoes. They also issued an orange code for air travel.

Lava was spotted 0.3 miles away from the top of Pavlof, which sits at 8,261 feet high. Ash and steam from the volcano can be seen 37 miles away in the community of Cold Bay. It is the second volcano to erupt in Alaska this month, after Cleveland.

Lava flowed down Cleveland yesterday but no ash clouds have been detected. It is 5,676 feet tall and had a 100-meter wide lava flow going down about a mile. The volcano also had a minor eruption earlier this month.

Pavlof, unlike Cleveland, is connected to the Alaskan mainland. Cleveland is on a separate island.

Cleveland is capable of sending ash clouds 20,000 feet above sea level.

"We think of the Aleutian Islands as being remote and desolate, but when you come up to 30,000 feet we are talking about 20 to 30,000 people there every single day,” U.S. Geological Survey scientist John Power said.

According to University of Alaska Fairbanks scientist Steve McNutt, 90 percent of aircraft flying to Asia, Europe, and North America fly over Alaskan airspace.

Since Cleveland is in a more remote location, it takes longer for the scientists to realize when there is an eruption.

Power said that it took them 40 minutes to find out about the “sizeable” May 4 eruption.