Geologically, the islets are a coral atoll, built on the Kyushu-Palau Ridge, the westernmost part of the Izu-Bonin-Mariana Arc system. The name Parece Vela has been given to the extinct back-arc basin that lies immediately to the east (the northern half of this back-arc basin is known as the Shikoku Basin). This back-arc basin was formed by seafloor spreading between the late Oligocene and Miocene. The Parece Vela Basin contains the longest megamullion in the world. The original Spanish name of the islets is normally used for the geological formations, hence, Parece Vela megamullion, Parece Vela ridge, Parece Vela rift or Parece Vela basin.