Earth’s seafloor is born in fiery eruptions along volcanic mid-ocean ridges. According to a new study published this week in Geophysical Research Letters, those volcanoes are surprisingly sensitive to the tides—and they just might have something to do with ice ages as well.

What’s more, all ten eruptions occurred during the first six months of the year, when Earth is moving farther away from the sun on its very slightly elliptical orbit. That’s when the sun’s tidal pull on Earth’s solid crust is diminishing in a way that also favors eruptions.

Those observations led Tolstoy to wonder whether seafloor volcanoes might also respond to the much slower but larger changes associated with ice ages.

During ice ages, massive glaciers overrun