What is a Pillow Lava?

Drill hole 2 contains some of the best preserved pillow lavas in the Archean rock record and we now have hundreds of meters of these unweathered, pillow lavas to study. Read more to find out how pillow lavas are formed.

Pillow lavas are formed when hot, flowing and still molten volcanic lava erupts onto the seafloor. Here it is rapidly chilled and forms a glassy skin with still molten lava inside. As the lava keeps er Photo (left) large pillow with a "crack out" fracture in the centre that was frozen in by rapid cooling upting this skin fills with lava forming large sub-spherical "blobs" known as pillows. These can be several meters across and accumulate on the seafloor as more and more lava erupts. Sometimes the new lava is fed through tubes onto the seafloor or can breakout through the outer skin of a pillow to feed another pillow. Just such a "crack out structure" is seen in this photograph, the sharp jagged crack down the middle of the rounded pillow was "frozen in" by rapid cooling and solidification of the lava before another pillow could form.

Photos show a large pillow with a "crack out" fracture in the centre that was frozen in by rapid cooling of the molten lava, and water worn pillow lavas from the river bed containing gas bubbles trapped by the solidifying lava and dark green glassy rims around their margins.

Photo credit: (left) Nicola McLoughlin (right) Hubert Staudigel