Pacific Ocean pillow basalt
The glassy crust has broken off the rounded surface of this pillow, exposing the dark, fine-grained basalt beneath. The radial pattern of fractures on the side is typical of pillows that cool quickly from their outer surface ot their center, quenched by cold seawater.
Loaned by the Geological Survey of Japan
Topic: Earth Science
Keywords: Japan, Lava, Magmas, Mid-ocean ridges, Ocean bottom, Volcanoes