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Geology 
at Hobbs Nature Reserve  

Hobbs Nature Reserve contains rock formation dating back to the Siluraian Period

The Ancient Geology at Hobbs 

The Silurian period

During the Silurian period (443.7 to 416.0 million years ago), Earth experienced significant changes, including the melting of large glaciers leading to rising sea levels and a more stable climate. This period saw the emergence of coral reefs and marked a crucial stage in fish evolution, with the rapid spread of jawless fish and the appearance of the first freshwater fish and jawed fish. Additionally, the Silurian provides the earliest evidence of life on land, including relatives of spiders, centipedes, and the earliest vascular plants.

Exposed Silurain rock at Hobbs

The section at Hobbs is only one part of an abandoned linear quarry that extends north-south for one kilometre along the ridge east of Longhope village. It provides a wonderfully exposed section through a series of reef-like bioherms and fossiliferous carbonate rocks that are Gloucestershire’s approximate equivalent of the Wenlock Limestone seen at Wenlock Edge in Shropshire. The accessibility at Hobbs allows it to provide source material for examination by groups of all ages and all academic levels. You can visit the Wikipedia page on Hobbs Quarry for more information. 

Geology Study

Investigations of the geology, especially the palaeontology, commenced 200 years ago when the quarries were active, but there remains much to research to extend our knowledge of these rocks and their setting in Silurian times. The Silurian, the briefest period of the Paleozoic Era, is characterised by distinct rock layers marking its beginning and end, though precise dates remain uncertain by a few million years. Its onset is marked by significant Ordovician-Silurian extinction events, during which up to 60% of marine genera perished.

For geologists and enthusiasts alike, Hobbs offers a glimpse into the deep past, a chance to witness the enduring legacy of ancient reefs and the geological processes that have shaped our world. It stands as a reminder of the Earth's rich history and the importance of preserving these natural wonders for future generations to explore and appreciate.

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Ballstone Reef

Ballstone Reefs

The fossilised reef-like mounds are called bioherms (known to the quarrymen as ‘ballstones’) with their associated sinuous drapes of overlying limestones. These are unbedded, very fine-grained limestones deposited by calcareous algae. 

Contact Us

If you have any questions or comments please contact us through our email: contact@hobbsnaturereserve.org.uk