The Aireys Inlet Volcano EarthCache
Hidden : 4/25/2014
Difficulty:
2.5 out of 5
Terrain:
2 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:




Spit point is a geological wonder – born of fire and sea between 24 and 29 million years ago

20million years ago, liquid lava at over 1000 degrees Celsius erupted from a volcano only metres from GZ. The lava cooled and crystallized to form dark, hard layer of basalt rock you can see at the base of the cliffs.

Another, more explosive volcano only 200m NE blasted ash and super-heated rocks into the air. They fell to earth and solidified to form a clayey, light brown rock called tuff. The tuff layer gets thicker in the cliff east of here and is studded with erupted rocks.

The basalt shore was flooded by a rising sea 24 million years ago. Sand and shelly fragments settling on the bottom of the sea slowly built up and cemented together to form the yellow limestone that now forms the cliffs upper layer.

The limestone is full of fossilized shells and other marine creatures. The unique Janjucetus whale fossil, found in limestone cliffs near Torquay, provides clues into whale evolution.

The basalt reefs here are special habitats. As the lava cooled and cracked, it created jumbled rock piles and zigzagging crevices – perfect refuges for sea creatures. Dark coloured basalt shores heat up more in the sun. On hot days, look for marine snails crowding onto the shady side of rocks at low tide.


This detail of the limestone´s lower boundary shows how sand and shells settled into, what were at the time, hollows in a basalt sea bed.
26 million years later, exactly the same process is occurring in the Marine Sanctuary´s rock pools.

To log this earthcache, please send me the answers to the following questions:
1. Look a the seastack near to GZ. You can see the basalt layer and the yellow limestone layer. Estimate the thickness of the layers. Do you see any tuff?
2. Do you think it´s possible, that there is a new erruption of the volcano in the next 100years? Explain your ideas!
3. Photos are very welcome but optional

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