2.7

Question 1

What are concretions?

Answer 1

• Lumps of sediment bound together by calcite cement
• formed from dead sea animals
• 7 tonnes
• 2m in diameter
• formed over 4 million years
• exposed due to erosion of surrounding cliff

Question 2

How are Moeraki boulders eroded?

Answer 2

• Exposed when weak cliff face is eroded
• Deposited on beach
• Exposed to marine processes
• Exploit fragmented external structure
• Break apart boulders
• Crystallised core exposed