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Discovering the Channel Islands and Explore the Geodiversity of Jersey

As this years Summer Solstice passes by our thoughts now almost certainly turn to the prospect of enjoying a relaxing holiday in a beautiful location where warm evenings are rewarded with a Kimmeridge Rum Spirit sundowner shared with friends and family. Maybe that next holiday hangout is nearer than you thought - maybe you are about to discover Jersey the largest of the Channel Islands only a short flight or ferry journey from the mainland.

Green Island Beach on Jersey - Image by Bam Perspectives
Green Island Beach on the south coast of Jersey - Image by Bam Perspectives

Sip back and enjoy this blog that explores over a billion years of geodiversity of this British Crown Dependency.

The Bailiwick of Jersey is the largest and most southerly of the Channel Island archipelago, including Guernsey, Alderney, Sark and Herm, just off the coast of Normandy in north-west France.

Jersey’s capital is St Helier. At only 8 kilometres long and 14.5 kilometres wide the island of Jersey has a unique geodiversity reflected in the island's landscape ranging from the rugged high cliffs of Les Platons, Le Pulec, Le Grand Becquet and St Ouen in the north to the low-lying coastal plain of sandy beaches between Gorey and St. Aubins.

Since 2009 the Government of Jersey has established 22 Sites of Special Geological Interest (GSSIs), with more expected to come, that have been determined to have unique geological qualities.

Jersey’s geology has been described in the press as “very rare” and "perfectly suited for Geotourism" all of which supports the Island’s bid by the Aspiring Jersey Island Geopark (AJIG) project established in 2021 to become a future UNESCO Geopark.

A German Observation Bunker on the North Coast of Jersey - Image by Jersey Tourism
A German Observation Bunker on the North Coast of Jersey - Image by Jersey Tourism

More information about this exciting geopark bid and the Island’s geological heritage can be explored by a network of walking paths, cycle routes, green lanes and by sea or simply visit the Jersey Museum & Art Gallery in St Helier for more information.

Cliffs overlooking Beauport Bay on Jersey - Image by Jersey Tourism
Cliffs overlooking Beauport Bay on Jersey - Image by Jersey Tourism

Located in the south-western English Channel in the sheltered Bay of St Malo between the coastlines of the Cotentin Peninsula and Brittany.

The Channel Islands enjoy a temperate sunny climate for much of the year that in combination with favourable soil conditions has helped to grow a trade in Lavender, Jersey Royal potatoes and dairy products from the grass fed Jersey cow whose milk contains: 18% more protein, 20% more calcium, and 25% more butterfat than ‘average’ milk compared to many other dairy breeds.

Interestingly, unlike traditional wine growing regions around the world that benefit from a bed rock of chalk as the preferred growing medium to deliver a wine's aroma and flavour. The combination of Jersey's rich soils laying above a bed rock of granite plus the climate has led to the Island developing its own unique terroir in terms of appearance, aroma and flavour. Most notable of Jersey's small vineyards is the IWSC award winning La Mare Wine Estate in St. Mary.

La Mare Wine Estate in St. Mary on Jersey - Image by Matt Porteous
La Mare Wine Estate in St. Mary on Jersey - Image by Matt Porteous

Their Le Mourier Sparkling Wine is an aged blend of Seyval Blanc, Phoenix grape varieties with an added drop of distilled grape brandy that gives it a crisp scent of lime, marmalade and citrus with a subtle spice aroma of vanilla. This has all the hallmarks and promise to be a perfect pairing on the palate with locally harvested Jersey oysters.

As you travel the Island of Jersey you will be struck by the number and size of the concrete military fortifications, bunkers, tunnels and repurposing of historic forts. These are the relics of an abhorrent time of Nazi occupation during World War II.

According to the House of Lords archive the British Government under Sir Winston Churchill declared Jersey as a demilitarised zone with no defences or having any strategic significance for Britain. The Island was viewed as an economic liability rather than a strategic advantage. On the 15th June 1940, the British Government decided that the islands would be left undefended. They were demilitarised and residents were given the option to evacuate.

Germany launched Grüne Pfeil or Operation “Green Arrow” and after a short period of bombing General Richthofen the Commander of the German Air Forces in Normandy demanded on the 1st July 1940 that Jersey surrendered. Subsequently German troops under the command of Hauptmann Gussek quickly occupied the Island. It was not until the 9th May 1945 that Jersey was liberated.

German Observation Bunkers on the north-west coast of Jersey - Image by Gareth O Sullivan
German Observation Bunkers on the north-west coast of Jersey - Image by Gareth O Sullivan

The building of the fortifications seen today were overseen by a German civil military engineering group called Organisation Todt named after the senior Nazi engineer Fritz Todt.

Monument to Liberation - Image by Max Burnett
Monument to Liberation - Image by Max Burnett

Headquartered in St Helier their building was known as "Bauleitung Julius" translating into "Construction Section Jersey". Organisation Todt made effective use of military geologists to assist in their fortification projects around the Island.

The goal was to make the Island into an impregnable fortress with the delusion that once they had won the war Jersey would remain a permanent outpost of the German Reich.

Organisation Todt forcibly recruited a workforce of over 6,000 men and women from across Western Europe, Eastern Europe and North Africa. Many of whom were forced to work to their death. More information is available from the Imperial War Museum and Liberation Route Europe Memorial.

Liberation Day is a Bank Holiday on Jersey and commemorated at Liberation Square in St Helier each year. Developed in 1995, the square marked the 50th Anniversary of the Liberation with a large bronze sculpture by Philip Jackson’s depicting a group holding the Union Flag at the centre of a fountain with 12 water jets symbolising Jersey's 12 parishes.

Jersey is an exposed outcrop of the Armorican Massif a geological region named after an ancient Gaul description of the French coastline known as “Armor” and covers a large area of northwest of France from Brittany through to the Channel Islands extending into the south west of England.

The area of the Armorican Massif or “North Breton Cadomian” has a complex geological history involving multiple tectonic events, periods of sedimentation, and episodes of granite intrusions and intense folding and faulting.

The Channel Islands were also located in the ice marginal region of North West Europe and south of the succession of glacial ice sheets of the Pleistocene Epoch where loess was deposited by the wind during the warmer interglacial periods.

St. Ouen's Beach with La Rocco Tower and Corbière Lighthouse in the background - Image by Gareth O Sullivan
St. Ouen's Beach with La Rocco Tower and Corbière Lighthouse in the background - Image by Gareth O Sullivan

The oldest rocks on Jersey, but not the oldest of the Channel Islands, are the late Precambrian silts and sandstone of the Jersey Shale Formation found in the centre of the Island that have been eroded over time to form the bays and inter-tidal reefs of St Ouen’s Bay on the west coast, St Aubin’s Bay on the south coast and the valleys of St. Peter and St. Lawrence.

Freshly shucked Jersey oyster - Image Max Burnett
Freshly shucked Jersey oysters - Image Max Burnett

It is these shores on the eastern coast of Jersey where the shallow waters between Jersey and Normandy have a tidal range that can reach up to 12 meters.

The inter-tidal conditions especially within the Royal Bay of Grouville is where the aquaculture business of growing and harvesting between 50 and 60 million Pacific Oysters (Crassostrea gigas) of various sizes and also “Bouchot” mussels happens.

Bouchot Mussels are grown by placing larval mussels on naturally made ropes wound tightly around wooden stakes called "bouchots" derived from the word for “wooden fence”. This is a traditional technique believed to date back to 1235 when a survivor of a shipwreck in the bay d’Aiguillon called Patrick Walton from Ireland noticed that the wooden stakes holding local fishing nets in place were covered in mussels.

Along with oysters and mussels the seas and rugged coastline around Jersey are rich in Brown Crab, Lobster, Scallops and Whelks.

The oyster beds in the Royal Bay of Grouville - Image by Gareth O Sullivan
The oyster beds in the Royal Bay of Grouville - Image by Gareth O Sullivan

Jerseys sediments date back to the Neoproterozoic Era dating between 700 - 400 million years ago and were laid down in a former deep marine environment before being influenced by metamorphism from a number of tectonic events.

First was a volcanic period when the area around Jersey was compressed and plutons of igneous andesite and rhyolite extruded between Fremont Point to Gifford Bay and St. Catherine's Bay to Anne Port where Lava flows can be discovered before becoming deformed during the later Cadomian orogeny.

Anne Port and Archirondel - Image by BAM Perspectives
Anne Port and Archirondel - Image by BAM Perspectives

Dating between 650 – 500 million years ago the Cadomian orogeny occurred. Named after the Latin for Caen (Cadomus) the capital of the French department of Calvados in the region of Normandy.

This was a time when the ancient supercontinent of Rodinia began to breakup and both sedimentary and volcanic rock formations were melted, folded and deformed plutons of diorite, gabbro and granite were formed.

Known as the Jersey Volcanic Group this trio of igneous extrusions make up three of the four corners of the Island of Jersey In the north west (St. Ouen’s), south east (La Rocque Point) and the south west (La Corbière Point).

La Corbiere Lighthouse - Image by Gareth O Sullivan
The La Corbière lighthouse on a tidal island south west of Jersey - Image by Gareth O Sullivan

The granite from Jersey was historically quarried from local quarries on the Island and used as a building stone as seen in many buildings along Commercial Street, and the exterior of the shopping district of Liberty Wharf in St Helier and the island fortifications including the original building of Fort Henry in Grouville.

Fort Henry found by the sand dunes of Royal Bay of Grouville known as "Long Beach" and dates back to 1772

Approximately 150 million years later after a period of sedimentation of limestones, sandstones, and shales in to a shallow marine environment this region was influenced by the Variscan orogeny. The area of Jersey would experience isostatic change as the level of the land rose up relative to the sea because of the influence of the mountain building event that formed the Alps and Pyrenees between 370 – 290 million years ago.

Over the millions of years that passed erosion by wind and rain of this raised land led to the formation of the coarse-grained Rozel Conglomerate locally known as "pudding stone" a feature of the north east of Jersey.

The youngest rocks and soils on Jersey are derived from both the Pleistocene and Holocene and highlight the glacial and interglacial periods of advances of ice into the temperate latitudes of the Northern Hemisphere during the Quaternary Period.

Jersey was not covered by glacial ice but a combination drift deposits of frost shattered rocks called Head and much finer silt washed and blown away from glaciers are found on the Island.

The Miniquiers sandbanks and nearby reefs - Image by Gareth O Sullivan
The Miniquiers sandbanks and nearby reefs - Image by Gareth O Sullivan

Sea level change over the last 10,000 years of the Holocene created the vast sandy submerged coastal landscapes such as the Les Minquiers also known as "the Minkies 15 Km off the south of Jersey as well as vast sandy beaches and sand dune systems including Les Blanches Banques in St. Brelade which is among the ten largest single dune systems in the British Isles.

Sea level change also created a number of wave cut platforms and raised beaches that can be discovered in the Islands own Ice Age Walking Guide.

The Island of Jersey packs a punch in terms of geodiversity from the influence of mountain building, sea level change, erosion, the ice age and occupation. The role of geodiversity has played its part in creating a provenance for some exceptional food and drink to be enjoyed during your holiday on the Island of Jersey.


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