Because spreading ridges are so deep and so remote, humans rarely witness volcanic eruptions along them. But the Juan de Fuca Ridge's proximity to oceanographic laboratories has enabled scientists to study its undersea volcanism in great detail. Since 1986, they have detected several eruptions.

	Cut Pillow Lava
	Pillow Lava

Magma that erupts on the sea floor is instantly enveloped by frigid ocean bottom water. The magma immediately adjacent the sea water freezes rapidly to glass, while interior portions cool more slowly to form glass studded with tiny crystals. Sea-floor eruptions commonly generate stacks of bulbous and tubular lava lobes that accumulate to look like a stack of pillows.