Flooding in Juneau: What is a glacial outburst?

This past week, a glacial outburst brought severe flooding to Juneau, Alaska. Here's how glacier outbursts work.

On Tuesday, a glacier outburst caused severe flooding in Juneau, Alaska, damaging more than 100 homes and businesses. The video above shows the dramatic rise and fall of water levels in Suicide Basin during the glacial outburst that caused this extreme flooding.

So what is a glacial outburst? A glacial outburst is a sudden release of water from a glacier or ice dam, often resulting from the failure of a natural barrier or rapid melting.

This week's flooding in Juneau occurred after a smaller glacier that retreated more than a decade ago left a smaller basin (Suicide Basin) that fills with rainwater and snowmelt each summer. When the water creates enough pressure, which happened this week, it forces its way under or around the ice dam created by the Mendenhall Glacier, enters Mendenhall Lake and eventually makes its way to the Mendenhall River.