Somewhere in the OR/WA/ID tri-state area, a spring surfaced in the Miocene. The liquid did as liquids will, and flowed downhill, rushing across the landscape. Gurgling, bubbling, and chortling across the territory later to become known as Oregon, it charged toward its confluence with the great basin of saltwater we now call the Pacific Ocean. When the torrent finally reached that shore, it playfully plunged in.
And froze solid.
Because this was no ordinary, aqueous, spring, but a vast cauldron of molten rock, likely in the range of 1200 degrees Celsius (~2200 F).
The two likely products of a basaltic lava entering water are breccia- shattered fragments- and pillows. Both are evident at Depoe Bay and in this photo. Below, I've highlighted a few of the pillows, balloon-like structures that form as lava enters the water, are quenched on the outer surface, then continue to fill for a bit.