Betty looked suspicious. She hadn’t read that anywhere, and she doubted any information she had not seen laid out in columns in a textbook.

Grant Glacier was a wide ribbon of ice winding out of the Quilak Mountains, white higher up and black lower down with a blue layer sandwiched between the two. “Why’s it black lower down?” Peter Mike said.

“Who remembers what happened on March twenty-seventh, 1964?” Ms. Doogan said.

There was a blank silence.

“Come on,” she said, and sang, “ ‘Rock and roll is here to stay, it will never die’-come on, you guys, you know this. Unless you’ve been propping your eyes open with toothpicks in class.”

Johnny Morgan finally opened his mouth. “Earthquake.” Anything to keep Ms. Doogan from singing again. Sheryl Crow she wasn’t.

“That’s right, Johnny,” Ms. Doogan said, beaming, “the Good Friday Earthquake of 1964. Nine-point-two on the Rich-ter scale. One hundred and twenty-five people were killed, some by the resulting tsunami as far away as Oregon and even Hawaii. The biggest earthquake ever felt in the United States in recorded history. And, by the way, eight of the top ten biggest quakes in U.S. history have had their epicenters in Alaska. Little bit of trivia there for you.”

They knew better. Ms. Doogan’s trivia had a way of showing up on tests. Once more Johnny threw himself into the breach. “How’s that make the glacier black on the bottom?”

“That same quake caused the mountain right next to it to shake into pieces.”

“There is no mountain next to it,” Alan Totemoff said.

“Exactly,” Ms. Doogan said. “The resulting debris fell onto Grant Glacier, in a layer that was three feet thick.” She demonstrated with a hand at midthigh.

Even Betty Freedman was impressed.

Like any good performer, Ms. Doogan had them from that moment and she was quick to press her advantage. “The edge of a glacier is a case study in giving birth.”