Complex sentence: 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 known as the "Organ Pipes" for which this park is named.
Split into simpler sentences: 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.