Sea Stacks and the 12 Apostles

Introduction to Sea Stacks

• Pillars of rock that emerge from the ocean, often found near coastlines.
• Serve as tourist attractions worldwide.

The 12 Apostles

• Located along the Great Ocean Road, Australia.
• Consist of 9 limestone-rich pillars (not 12).
• Each pillar is up to 50 meters (164 feet) tall.
• Known for their vertical stature above the Southern Ocean cliff walls.
• Part of Port Campbell National Park in southern Victoria, Australia.
• 10 kilometers east-southeast of Port Campbell.
• Formation expected to undergo future changes due to erosion.

Geological Composition

• Younger rock formation, aged between 14-8 million years.
• Composed of Port Campbell Limestone.
• Limestone is organic, made from ancient sea creatures.
• Formation underlain by Gellibrand Marl (silty and muddy rock).

Historical Ocean Changes

• 15 million years ago, the site was under a much larger ocean.
• Sea levels were 30 meters higher than today.
• Environment was ideal for coral reefs and shell-bearing creatures.
• Limestone built up over 6 million years to 50 meters thick.

Erosion and Sea Stack Formation

• Sea levels decreased, leaving a large cliff face.
• Acidic rainwater created crevices in limestone.
• Cracks expanded into vertical pillars.
• Formation of sea stacks through erosion.
• Future sea stacks expected to form as current ones erode.

Current and Future State

• One sea stack collapsed in 2005.
• Remaining stacks expected to erode over millions of years.
• Ongoing natural process of destruction and formation of new stacks.

Conclusion

• The 12 Apostles are a dynamic geological feature.
• Reflect ongoing natural processes shaped by ocean levels and erosion.

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