Pillow basalt and palagonite, part of Columbia River Basalt Group, formed by lava flowing into a lake during the Miocene.
Marli Miller / Alamy Stock Photo
Image ID: W006HB
Note the jointed basalt above the pillows --and the transitional nature of their contact. The lava first poured into a lake to form the pillows, but then filled the lake and the later part of the lava flow simply flowed over land!
Location: Oregon, USA