The coastline of the southern Tasman Peninsula is composed of giant dolerite sea columns that protrude up to 300 metres from the sea. The distinct elongated shape are the property of the dolerite; a mafic (oceanic) rock that intruded beneath the surface of the earth as sills (parallel to the bed) or as dykes (across the bedding planes).
The hexagonal, prismatic column shape is termed columnar jointing. Dolerite forms this way because the magma cooled from the outside toward the centre surrounded by more or less consistent temperatures. These joints radiate outward from the centre of each column, which themselves form perpendicular to the flow base of the source magma (or lava if the rock was extruded at the surface, such as basalt).
As you walk to the very end of the track (GZ) at the top of The Blade you will be surrounded on three sides by rock, with one rather unique block directly in front of you at head height, that blocks your direct view of Tasman Island. You need to answer the following questions about this rock.
1) Is this rock an example of columnar jointing?
2) What feature(s) of the rock gave you your answer to question 1?
3) Why do you think the edge of rock facing you is different to other rocks around you?
3) OPTIONAL - take a photo of yourself somewhere at the top of the Blade (that doesn't give away the rock in question!)
Please take care as you walk around this amazing place. Take extra care in high winds. There are no fences or guard rails to protect you from falling, and extreme caution should be exercised. Remember you are in National Park so respect your surroundings.