The reef is named after Horomātangi (Horo-matangi),[1] the tāniwha or water monster of the lake, who is said to reside in a cave adjacent to the nearby Motutaiko Island to the south.

The reefs are at a high heat-output geothermal hot spot area within the Taupō Volcano.

[7] Recent periods of volcanic unrest of the Taupō Volcano have been associated with earthquake swarms centred in the area of the Horomatangi Reef.

From February to October 2022 during a period of volcanic unrest the reef had inflated upwards by a mean of 24 mm (0.94 in) relative to other reference points around Lake Taupō.

[8] A shallow magnitude 5.7 earthquake occurred on 30 November 2022 causing a further sudden upwards inflation of 180 mm (7.1 in), being the largest amount of uplift ever recorded to date for the reef.