Project information

CAREY, Dr Rebecca
University of Tasmania
Australia (or home country)

Project aim

Heard Island is an active sub-Antarctic volcanic island located in the southern Indian Ocean and is the surface exposure of the second largest submarine plateau on Earth, the Kerguelen Plateau (Fig. 1). It is an Australian territory and together with McDonald Island is UNESCO World Heritage listed. The volcanic history of Heard Island is poorly understood. This project will determine the absolute ages of key geological formations, which together with historical and recent remote mapping via satellite images will constrain the geological evolution of Heard Island.

The technique used to determine the ages will be 40Ar-39Ar incremental heating dating, a method that has been used successfully to date young lava flows in volcanic systems world-wide. The age determinations will enhance our understanding of relative timing, frequency and volume of past volcanic events on Heard Island, which is highly relevant to the geological evolution of the greater volcanic Kerguelen Plateau.

Project milestones

Summary of the project achievements 2017/18

We have investigated the ages of rocks collected from Heard Island, Australian Antarctic Territoty to construct a temporal sequence of lava producing events on Heard Island.
The new ages for Heard Island lavas have revealed that lava-forming effusive volcanic activity over the last 80 thousand years and at least 11 effusive +/- explosive eruptions over the last 26 thousand years. Our results also demonstrate that the chemical compositions of lavas erupted varied across relatively short time frames from single volcanoes.

Summary of the season 2016/17

Heard Island is Australia's currently active hot spot volcano and is situated in Australian Antarctic Territory. Volcanism on Heard Island is observed today through satellite imagery, however we know very little about the volcanism that has built up the island. This project used rocks collected in historic expeditions to the island, as well as those in 2015/2016, to understand the geological history of the island. Our achievements include: collecting geochemical data that provides a window into the mama plumbing system from the deep earth to eruption at the volcano's summit, collecting age dates through isotopic methods of lavas on the island, and finally collecting the metadata and storage locations of Heard Island samples across the globe. We have learned that hot rising magma melts the underlying crust beneath Heard Island, causing the eruption of highly variable magma compositions. We have learned that volcanism on the island seems relatively continuous back to 60,000 years ago.

Summary of the season 2015/16

The project team have conducted sample preparation and analysis for age determinations on six rocks from Heard Island in Australia's Antarctic Territory. These age dates have enabled us to understand the growth of Heard Island through volcanic eruptions over the last 100,000 years. The project team also participated in the 2016 voyage to Heard and McDonald Islands on board the CSIRO's RV Investigator. We collected multiple submarine rocks and pumice clasts that will be analysed in the year to come. These are the first ever rocks collected from the submarine edifice of Heard and McDonald islands and will provide data to determine the genesis and timing of volcanism on the islands. The project team also observed and characterised a lava eruption from the peak of Heard Island in February during the voyage, which will be written up for publication in the Australian Geographic magazine later this year.

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