Fingal Head boasts some of the most spectacular examples of columnar jointing to be found in the whole of NSW. The name "Fingal Head" is actually derived from a fabled Scottish hero who was involved in the folk story surrounding the creation of Fingal Cave in Scotland and the Giant's Causeway in Ireland. The local indigenous Goodjingburra clan's name for Fingal Head is Booninybah - Home of the Giant Echidna: "Booniny" means Giant Echidna. The spectacular columns of Fingal Head resemble the spines of an echidna, and so the Goodjingburra believe that the spirit of the echidna inhabits the headland.
Geology
The columnar basalt lava flow at Fingal Head extends underwater to Cook Island (named after Lieutenant James Cook who explored the east coast of Australia in 1770). The lava is thought to have come from the prehistoric Tweed Volcano and is known as "Lismore Basalt"; predominantly tholeiitic with occasional alkaline types. This headland is an outcrop of Tertiary basalt aged 22 - 24 m.y. - part of the widespread volcanic activity in northeastern NSW and southeastern Qld which produced many well known volcanic features. The fresh basalt appears dark in colour due to its mineral content (high in plagioclase feldspar and pyroxene, low in silica).
The jointing, clearly evident at Fingal Head is caused by contraction: as lava cools from the outside toward the centre, shrinkage cracks develop, usually forming hexagonal patterns (the shape of the columns is attributed to tensional stress).
Getting There
Fingal is located in the Tweed Region just south of the Tweed River. Access to the headland is available via two routes, the most impressive leading to the top of the headland. For this route follow Fingal Head Road into Lighthouse Parade and park in the area at the end of the road. A track leads off from the northern side of the road. This track leads to the lighthouse and headland. Alternately, the base of the formation can be accessed from the beach by following Fingal Head Road, turning into Main Road and then into the parking lot at the end, where there is beach access. It is about a 400m walk south along the beach to reach the headland.
Tasks
Please email us the answers to the following with the cache name. We will contact you if more information is required. Logs that have not had the the answers sent to us will be deleted. Please do not include your answers in the logs.
1. Look at an area of columns and indentify any 3,4,5 and 7 sided columns instead of the regular 6 sided features. Approximately what percentage are not 6 sided. Why do you thing they are not 6 sided/
2. Why do you think the columns are vertical and which axis did the lava flow. Did the lava cool fast or slowly and how does this impact on size.
3. Estimate the height of the larger pipes (above sea level).
Optional. Take a picture with your GPSr and enjoy!