Freeze corer:
To extract [Lake Crawford’s] layered sediments, the team used a tool called a “freeze corer,” but more affectionately known as “the frozen finger.” The long aluminum wedge was filled with a mixture of alcohol and dry ice, making it much colder than the surrounding water, soil and air.
They suspended the freeze corer from a tripod and lowered it through a hole in the raft. Down, down it went, through 75 feet of water, until finally it sank into the squishy mud on the lake bottom.
Then they waited. It would take about 40 minutes for the lake sediments to freeze onto the corer’s chilly surface. [“HIDDEN BENEATH THE SURFACE,” Sarah Kaplan, WaPo]
