BONDI Its geologic past; its 150 years of change; its future Bruce - - PowerPoint PPT Presentation

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BONDI Its geologic past; its 150 years of change; its future Bruce - - PowerPoint PPT Presentation

Sep 26, 2022 119 likes •729 views

BONDI Its geologic past; its 150 years of change; its future Bruce Thom www.wentworthgroup.org Why is Bondi so iconic? Proximity East Australian Current Sydney climate Topographic setting Geology- geomorphology Geological

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BONDI

Its geologic past; its 150 years of change; its future

Bruce Thom

www.wentworthgroup.org

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Why is Bondi so iconic?

  • Proximity
  • East Australian Current
  • Sydney climate
  • Topographic setting
  • Geology- geomorphology
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Geological Evolution

STEP 1 Fold-Belts 500-300 my

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Geological Evolution

STEP 2 Sydney Sedimentary Basin 300-200 my Volcanic intrusions 150 my

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Geological Evolution

STEP 3 Opening Tasman Sea 80 – 60 my

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Geological Evolution

STEP 4

  • Subsidence continental margin
  • River valley incision

60-10 my

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Geological Evolution

STEP 5

  • Continental sea-level rise
  • Planation inner continental shelf
  • Formation of cliffs
  • Sand migration to north

10 - <1 my

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Geological Evolution

STEP 6

  • Last Interglacial to Last Glacial

Maximum

  • High to low sea level (-120m)

140,000 – 15, 000 yr

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Geological Evolution

STEP 7

Postglacial Marine Transgression to “Stillstand”

15,000 – 6,500 yr 6,500yr – to present day beach-barrier-lagoon

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Inner Shelf Sand Bodies

3 stage development 12,000 yr 7,000 yr Present sea level

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Beach Dynamics

Closed compartment of quartz sand Rip cell dominated

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Pre-European Occupation

Shelf plain Beach to estuary Rock platform to cliff

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Early European Land Grants

Roberts “Bundye” 1811-1851 Hall/O’Brien 1851-1882 Public Resumption 1882 Council Trustee 1885

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Late 19th Century

Destabilize dunes Sewer Outfall 1889 Attempts to stabilize dunes Infill lagoons

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Early 20th century

Continued stabilization Baths Completion of Promenade 1923 Dune removal - subdivision

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Mermaid Rock Ben Buckler

Rock platforms Storm events July 1912 Origins of The Rock

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Mid 20th Century

Piers Real estate consolidation World War II

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Late 20th century events

May – June storms 1974 November Storm 1987 (2007) Sewer Outfall offshore Olympic Stadium 2000

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Bondi Today

Resilient dynamic closed system

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A Sustainable Future?

Can Bondi adapt to impacts of climate change? Need for nourishment: when? Collapse of cliffs: when?

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Thank you

www.wentworthgroup.org www.australiancoastalsociety.org