Volcanic basalt rock columns.- The Organ Pipes

https://en.wikipedia.org/wiki/Organ_Pipes_National_Park
Within Organ Pipes National Park, the valley walls of Jacksons Creek expose Pleistocene volcanic rocks of the New Volcanic Group. These 2.5 to 2.8 million year-old basalt lavas, commonly known as trap rock, fractured during cooling into vertically standing, hexagonal basalt columns. These columns are locally known as the "organ pipes" for which this park is named.