Institute
University of Auckland
Time & Place
Thu, 14 Sep 2023 13:00:00 NZST in ER 263
Abstract
A controversial, yet tantalizing recent theory suggests that global rising sea levels can cause an increase in the frequency of volcanic eruptions and earthquakes. Such connectivity between the atmosphere, hydrosphere, and geosphere at 1000-1,000,000-year time scales however is difficult to prove, due to a lack of well-dated, well-preserved, long sediment records. Co-located volcanic eruptions in the Taupō Volcanic Zone and earthquakes associated with the Hikurangi Subduction Margin, coupled with new long (>900 m) sediment marine records over multiple glacial-interglacial cycles, make Aotearoa-New Zealand’s, North Island, plate-boundary an ideal location to constrain these processes.
During this talk, Lorna will highlight some the work that she and her team of 20 international and national researchers are doing to answer this question, as part of a fully funded Royal Society, Marsden project. The project uses International Ocean Discovery Program (IODP), Expedition 375 sediment cores extracted from more than 3km water depth within the Hikurangi Trough to focus on understanding the connections between glacio-climatic change, volcanism, and earthquakes over the last ~2 million years. The team have unravelled details of past seafloor processes that are closely coupled to changes in climate and ocean conditions. During the last glacial maximum for example, about 20,000 year ago, there was a sixfold increase in the delivery of sediment to the deep ocean, with unprecedented values of 1 m of sediment accumulation every 100 years. Today these systems are choked with sediment, as they are shed off an uplifting and occasionally explosive landmass. It is almost incomprehensible to imagine the magnitude and ferocity of natural physical and biogenic processes in the past.
Biography
Dr Lorna Strachan is a leading Aotearoa-New Zealand researcher who uses sedimentological observations to disentangle physical processes in the deepest depths of the ocean. In the last decade Lorna has worked on both modern and ancient marine sedimentary systems around Aotearoa. As such, she is one of our rare specialists whose work simultaneously bridges terrestrial outcrops and deep ocean deposits. She seeks to understand far-reaching physics-based sedimentary processes that operate on continental slopes, basin plains, and ultimately deep ocean sinks. In the last 6 years she has focussed on the Hikurangi Subduction Margin working with Integrated Ocean Drilling Program (IODP), NIWA, GNS Science and a large team of post-graduate research students. Using a range of cores from across the margin to understand links between sediment deposits, dispersal pathways, and flow triggers, including earthquakes and large storms. The Kaikōura Earthquake in 2016 providing the ideal test case to understand this hypothesised link.
Lorna is passionate about teaching and communicating science. She is an experienced lecturer at the University of Auckland and has established a reputation for innovative, excellent, research-led teaching. She gives excellent research talks and in 2020 won the inaugural Geoscience Society of NZ People’s Choice Best Talk Award for her talk entitled: “How did the Kaikōura turbidity current flow?” where she gave an exciting presentation highlighting an exceptional shallow sediment core data set and its implications to our generic understanding of turbidity currents. A gifted orator, she is animated and engaging and can explain complex ideas in simple terms.