Anthropocene geology: old and new rocks at Henley Beach
Thursday October 7th 2021
Mawson Lecture Theatre
Department of Earth Sciences
North Terrace Campus
University of Adelaide
Dr Laurence Campbell
In April-May 2020 travel and human contact in Adelaide were limited by the COVID-19 pandemic. In place of activities with the Field Geology Club I was constrained to “isolation geology” in my local area. As a result I found that the rocks in the sand at Henley Beach show a surprisingly large variety of types, while boulders in the most recent sea wall (all washed clean) show many geological features. Thus, for a 50th-anniversary event of the FGC, I suggested that Henley Beach could serve as a base for a treasure hunt for children of all ages and for teaching some aspects of geology.
I will show pictures of various phenomena that can be seen in the boulders in the sea wall, including cross-bedding, mineral veins, folding, fossils and dendrites, to show the potential for demonstrating basic geology. I will then show examples of the wide variety of the rocks and pebbles in the sand.
There are “rocks” on the beach that are obviously of human origin, such as glass, concrete, bitumen, pottery and artificial stone. Initially I assumed that the other, natural, rocks on the beach came through erosion of parent rock bodies south of Adelaide and arrived at Henley beach via the prevailing currents that move material northwards. However, as many of them are not associated with the eroding strata on the coast, I considered other options, including direct transport across the Adelaide plain, debris from buildings and sea walls damaged by the sea, formation within sand dunes (modern and ancient), formation on the beach, formation on submerged objects and inclusion in sand brought in from elsewhere.
To investigate these sources I will show historical pictures, look at buildings in the area, and make comparisons with other beaches. The latter will include the beach at Tennyson Dunes, which are the last true remnant of the Adelaide metropolitan coastal plains. I will also look at the sand dunes at Henley, where recent storms have exposed cross sections that show artificial and natural components. This is to give background for our upcoming excursion, in which we will consider the question: “Are the rocks in the sand at Henley Beach there naturally, or are they the result of human activity?” That is, are we looking at an example of the Anthropocene – the proposed geological epoch dating from the commencement of significant human impact on Earth's geology and ecosystems?
Dr Campbell is a physicist specializing in computer simulation of electron-driven processes in planetary atmospheres. He has been a member of the Field Geology Club for about 15 years.
PLEASE NOTE that current restrictions require masks to be worn, and everyone must sign in using the QR code or by providing contact details on the attendance sheet. FGC has a limited number of masks available if you forget to bring one. Please arrive early in order to complete formalities.
ZOOM. The meeting will be zoomed, technology willing! The link will be posted nearer the time and members will be notified of it by email.