Sugarloaf Reserve: A Dissected Scoria Cone

Scoria Cone – Scoria cones are the most common type of volcano. They are also the smallest type, with heights generally less than 300 meters. Scoria cones of the Lyttelton Volcanic Complex are parasitic cones generated by eruptions on teh flank of the main volcano.
Volcanic Bombs are molten rock projectiles that are thrown out of a volcano and then cool in mid-air becoming “bombs”. They can range in size from being small as 10mm to 64cm. Based on where they land compared to the crater it can tell us how powerful the eruption was and the kinetic energy it was exerting.
A volcanic block is a fragment of rock that measures more than 64 mm in diameter and is erupted in a solid condition. Blocks are formed from material from previous eruptions or from country rock and are therefore mostly accessory or accidental in origin.
A volcanic dyke is usually a more or less vertical sheet-like magma body that cuts through (intrudes) older rocks. Most dykes can be described as fractures into which magma intrudes or from which they might erupt.
Ccool features we can observe in this outcrop are dykes, both clastic and non-clastic types. Unlike volcanic dykes, clastic dykes form when sedimentary material fills an open fracture resulting in a crosscutting feature.

This outcrop is a road cutting along the southern side of the Summit Road at the base of the Sugarloaf Reserve. Take a walk along the outcrop and see if you can point out the contacts between different eruptive deposits.
As you walk from the car park along the grass verge you are walking away the vent of the scoria cone.
Can you see the change from large to smaller volcanic ejecta, blocks and bombs away from the carpark reflecting increasing distance from the vent?
Look for the dip of the layers within the deposits, these should be dipping away from the vent. Volcanologist use these to define the size and shape of the volcano.
Can you spot a volcanic dyke? (Look for solid lava). Did this come before or after the scoria cone erupted?
Can you find the clastic dyke? (Look for a subvertical crack, infilled with a jumble of ash and rock fragments)