Geology - Copper Coast UNESCO Global Geopark

The oldest rocks of the Copper Coast were formed 460 million years ago during the Ordovician period. At this time, the Copper Coast was part of a Continental margin, located under the sea near the South Pole.

As one continental plate slipped under another due to plate tectonics, magma rose from the depths of the earths mantle until it erupted in two separate volcanoes through the ocean floor where the Copper Coast was located. The first volcano erupted into and through the ocean floor. This created the dark coloured mafic volcanic rocks found along the coast – predominantly Andesite and Basalt. These rocks are part of the Bunmahon formation.

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The Sea Became Quiet

When the first volcano switched off, the sea became quiet again allowing shellfish to develop. During this period the calcareous (calcium rich) mudstones and siltstones were laid down. A unique species of Trilobite is found in these rocks which are part of the Tramore Limestone formation.

A second volcano, more explosive than the first one erupted around 455 million years ago. The magma from this eruption was more felsic and created the range of rhyolitic and breccia rocks found around the coast. It then switched off and the Copper Coast moved northwards, with its continent, towards the Equator.

The Copper Coast was now on land and during this time (the Devonian period) around 390 million years ago, the Copper Coast was home to a dry desert landscape with occasional flooding. This environment created red sandstones and conglomerates. As tectonic movement continued, these rocks were uplifted during mountain forming processes about 360 million years ago.

About 2 Million Years Ago

The Copper Coast kept on moving as the continental plate of which it is a part moved due to continuing plate tectonics to reach its present day position. About 2 million years ago, ice sheets and glaciers covered the land and while moving slowly, eroded the rocks underneath and shaped the landscape. When they melted at the end of the Ice Age, about 12,000 years ago, the glaciers dumped their load of boulder rich clays, topping the underneath bedrock. This formed the glaical till seen along the tops of the coastlines cliffs.

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