WILLOW, Alaska - New tremors at Alaska's Mount Redoubt are prompting speculation that the volcano could be in a phase that will lead to more instability.

The 3,100-metre volcano erupted six times Sunday and Monday, spewing clouds of gritty ash high into the sky.

A volcanologist at the Alaska Volcano Observatory said Tuesday that Redoubt was exhibiting activity that could indicate it is creating a formation called a lava dome.

Volcanologist Peter Cervelli said such a formation can collapse, creating more ash plumes and mudflows.

The eruptions so far have sent clouds of the abrasive ash drifting across communities north of Anchorage. Cervelli says the eruptions also triggered 35-kilometre volcanic mudflows.

Redoubt is roughly 160 kilometres southwest of Anchorage.