Lord Howe Rise

Geology

The Lord Howe Rise is associated with seafloor spreading which also resulted in the creation of the Tasman Sea. The geology has not yet been characterised as well as other parts of Zealandia but when previous samples are analysed with current geological techniques they fit with the Zealandia hypothesis. The seafloor is known to be dominated by soft sediments and the highest quality recent survey only mapped approximately 25,500 km² (9,800 sq mi) of the western flank of the rise which is less than 1% of the total area of the rise. In this area about 0.1% of the rise's seafloor was classed as hard substrata based on a combined area of 31 km² (12 sq mi) for 16 volcanic peaks. Sandstone rocks dredged from the central Lord Howe Rise contained granite pebbles that were in the range 216–183 million years old. It was rifted away from Eastern Australia in association with a mid-ocean ridge that was active from 80 to 60 million years ago, and now lies 800 kilometres offshore from mainland Australia.

The Lord Howe Rise contains a line of seamounts called the Lord Howe Seamount Chain which formed during the Miocene period when this part of Zealandia existed over the Lord Howe hotspot. One rhyolite sample has been dated at 97 million years drilled on the southern Lord Howe Rise. Lord Howe Island was the last volcano to erupt on the rise 6.5 million years ago.