In late 2013, scientists began to notice something strange happening in the Gulf of Alaska: The temperature of the sea surface was much warmer than usual.

Then in early 2014, warmer waters also started appearing about 125 miles off the West Coast of the United States. By the fall of that year, the warm area extended all the way to the coast. The warming persisted along the California coast and other parts of the Pacific during most of 2015 and into 2016. In some places temperatures were more than 10°F above average.

As scientists struggled to figure out what was going on, they began calling the mass of warm water “the Blob.”

Now a team of scientists has mapped the life story of