Photo 1c. Pillow lavas in the Canada Falls Member of the Frontenac Formation near Canada Falls and Seboomook Lakes in northwestern Maine. They are slightly more than 400 million years old. This view shows the internal structure common in some pillows. The outer crust is generally fine-grained and evenly textured. The center here shows former gas bubbles that are now filled with calcite. Geologists call open gas bubbles that are preserved in the rock vesicles. When they are filled with a mineral they are called amygdules. (Photo: R. Marvinney)

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Last updated on October 6, 2005

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