The big rock, the “Rock of Ages” in Coupeville behind Smile Cafe, was once part of a glacier.

It’s what geologists call an “erratic,” or a boulder left behind as a deposit from glacial flow.

That’s what geologist Grant Heiken taught his audience of more than a dozen people on Wednesday at the weekly half-hour or so “PorchStories” held on the porch of the Island County Museum. Heiken talked about the ways Island County was once shaped by glaciers long ago and why our land looks the way it does.

All of Coupeville was once under ice thousands of feet thick, he said, putting pressure on the land and depositing silt, sand and depositing erratics throughout local areas. Using a map, Heiken pointed out the curves in the land carved out by glacier movements.

Over thousands of years, the glaciers melted and the land rose up once the pressure was removed, and the sea rose up too.

Did I forget anything? Heiken asked his audience at the end of his talk.

“When will our next earthquake be,” came the answer.

Heiken checked his watch and jokingly answered, “a week from Thursday.”

Next Wednesday, at PorchStories there will be a “Musical History Tour,” which will be a mix of pioneer-era songs along with Central Whidbey history.