The oldest rocks on Lundy are the fine grained sandstone and slates that form Castle Hill, Lamentor and Rat Island. These rocks were formed as sediment settled in shallow seas towards the end of the Devonian Period around 370 million years ago. They are similar to rocks on tbe North Devon coast around Woolacombe and Saunton. If we found any fossils on Lundy we could make a better date for their formation. So far, no fossils have been found...

The oldest rocks on Lundy are the sandstones and slates around Castle Hill. These rocks were formed as sediment in shallow seas towards the end of the Devonian Period around 370 million years ago (mya). They are similar to rocks on the North Devon coast around Woolacombe and Saunton.

300-275 million years ago : Variscan Orogeny - the birth of the Variscan Mountains

Time passed and sands and silts in shallow seas were turned into rocks. Then these rocks were turned into mountains by a continental collision. The old rocks of Lundy were in a valley between mountains in South Wales and mountains in South West England. The Cornubian massif - the line of granite that stretches from Dartmoor to the Isles of Scilly were part of the backbone of these mountains.

Time passed and sands and silts in shallow seas turned into rocks. This rock turned into the Variscan mountains by the collision that created Pangaea 300-275mya. The old rocks of Lundy were in a valley between mountains in South Wales and mountains in South West England. The line of granite that stretches from Dartmoor to the Isles of Scilly were part of the backbone of these mountains.

More time passed. Mountains became deserts became shallow seas.

More time passed and these mountains became part of a vast hot desert of shifting red sands. These sands can now be seen in the red sandstone rocks and soils of Exeter and south east Devon.

British Cenozoic Igneous Province

65 million years ago Europe and North America were still joined. A hot upwelling from the Earth's mantle started to melt the rocks between them. This forced the continents apart, created Iceland and produced volcanic activity in Canada, Greenland, Ireland and the United Kingdom. The basalt flows of the Giant's Causeway and Staffa where formed at this time, as were volcanoes in Skye, Ailsa Craig, and Arran.

65 mya Europe and North America were still joined. A hot upwelling from the Earth's mantle started to melt the rocks between them. This forced the continents apart, created Iceland and produced volcanic activity in Greenland, Norway, Ireland and Scotland. The basalt flows of the Giant's Causeway and Staffa where formed at this time, as were volcanoes in Skye and Arran.

Lundy's granite is the the furthest south of this activity in Britain. The Variscan orogeny had weakened the crust allowing molten rock to rise towards the surface. The Lundy granite solidified 2-3km below the then surface of the Earth around 60 million years ago Thin lines of softer dolerite and harder trachyte cut through the granite and surrounding rocks forming dykes.

Lundy's granite marks the furthest south of this activity in Britain. The Variscan mountains had shattered the Earth's crust around Lundy leaving faults and thinner crust. This allowed molten rock to rise towards the surface. The molten rock solidified into the Lundy granite 2-3km below the surface of the Earth around 59mya. Thin lines of softer dolerite and harder trachyte cut through the granite and surrounding rocks forming dykes.

Was there a Lundy volcano? Arguments have shifted backwards and forwards. The Lundy granite was to small and too far underground to have created a volcano. Volcanoes shatter the rocks around them as they forced their way to the surface, creating dykes in the process. The dykes around and through Lundy could be evidence of this. Volcanoes also produce ash and lava. So far no geological record of this ash has been found.

The Earth never sleeps, but keeps moving, raising seas and submerging lands. Movement along surrounding faults has raised Lundy to the surface. Seas, rivers and ice have eroded the older, softer sandstones and slates, exposing the hard granite beneath. Lundy as we know it was born.


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