THE LIZARD

Not only is the Lizard peninsula Cornwall's and Britain's most southerly point, but its geology, landscape and flora are really very special too. Nowhere else in Cornwall can boast such a density of nationally recognised Sites of Special Scientific Interest (SSSI's) or regionally important county geology sites (formery known as RIGS).

See the Lizard geological timeline >>

Why is this? The answer is that the rocks on the Lizard are totally different from the rest of Cornwall. The most extensive (20 square miles) is the serpentine which is largest outcrop of such rock in mainland Britain and is found nowhere else in England. When Queen Victoria and Prince Albert visited the area in 1846, they were so struck by serpentine's unusual characteristics, that their ensuing royal patronage spawned an industry of architectural and decorative stone working that continues, albeit somewhat diminished, to this very day.

Originally this altered peridotite was thought to be the root of a volcano, but it is now recognized to be part of the Earth's mantle, today normally 10's of kilometres below your feet, which was bulldozed onto the newly evolving Cornish mainland in front of an advancing continent. The actual junction between the Earth's mantle and the crust is today exposed (by a chance freak of nature) on the foreshore at Coverack. This is why you will often see visiting groups of university students on the beach investigating the relations between the serpentinised mantle peridodites and the overlying crustal gabbros. It was a Croatian meteorologist called MOHOROVICIC (having constructed his own seismograph to study earthquake shock waves) who discovered the distinct boundary that exists between the lighter crustal rocks and the denser mantle rooks - and his name is given to this junction. Today we have shortened it to the MOHO!

Between Coverack and Kennack Sands there is a marked narrow promontory known as Carrick Luz. This is the remains of a great fissure in the serpentine that acted as the feeder for the overlying gabbro. In a few places (around The Manacles, Leggan Cove and the West of England Quarry at Porthoustock) instead of gabbro we can see dolerite and basalt dyke swarms that poured lava up through the gabbro onto the ancient sea floor. The actual lavas have since been removed by erosion or metamorphosed almost out of recognition.

Some of the oldest known rocks in the whole of Cornwall (500+ million years), occur around The Most Southerly Point - the Man of War Gneiss and the Old Lizard Head mica schists. The gneiss, with its corrugated texture, can be seen only as boulders on the beaches around The Most Southerly Point. They have been brought in by the waves from the offshore reefs, such as Shag and Labham Rocks. Another rock unique to the Lizard is the Kennack Gneiss, no prizes for guessing where it is best exposed.

There is a huge time gap (350 million years) between the great events that emplaced the rocks of the Lizard on Cornwall and today. It is becoming clear that many of the faults that control the development of the current shape of the coast and the location of the inland valleys, had formed in the first 75 million years after the Lizard was thrust up. It is within these and associated cracks that you find spectacular minerals, very different in nature from those associated with the granites and known as zeolites. Particularly fine collections are to be seen in the Helston Folk Museum and the Rashleigh Gallery at The Royal Cornwall Museum in Truro.

It is probable that much of Cornwall and the Lizard were covered by the high sea levels that deposited the Chalk elsewhere in Britain 65 million years ago. Inland the evidence has been eroded away but flint (weathered out of chalk) is regularly washed up along the south coast, perhaps from the still existing bed of Cretaceous rocks under the sea off Black Head and The Lizard Point. Nearby Loe Bar (SW643243) is composed of 86% flint!

Just before the turn off for Coverack on the main Helston-St Keverne road there is a small exposure of quartz-rich pebbles and cobbles of Tertiary age, probably deposited 25 or more million years ago and derived from the killas and granites north of the peninsula. There is small picnic area here... treat it with respect, for this really is ancient ground. You can see the quartz Crousa Gravels on the banks of the little pool here. This area is a RIGS.

Since these gravels were laid down there has been a tremendous amount of erosion. Much of the Peninsula - being composed of hard, dense serpentine gabbro and schists - has remained relatively high and treeless, whereas the softer Kennack Gneiss, fault zones, and killas country (The Meneage) that arcs around the Peninsula have been eroded into deep wooded valleys.

Each district of the peninsula has been uniquely shaped by its underlying rocks and nowhere is it more evident than near Lizard town itself. Here you can see today a vast difference between the fields to the south of the village - and those a little further north and west. The very tip of the Lizard is composed mostly of schists and these are quite fertile and grow cauliflowers and potatoes. Whereas, close by (to the north and west) you will see heathland that is quite barren in appearance and this overlies the ultrabasic serpentine with its poor soils. Perhaps you'll even be lucky enough to get a glimpse of the emblem of Cornwall itself - the Chough - now breeding in this part of the Lizard again, after an absence of many years.

Serpentine and gabbro produce magnesium or calcium rich soils and it is the resulting alkalinity of the soils on these parts of the Lizard that has enabled a large number of quite rare plants to thrive here, such as dropwort, salad burnet, bloody cranesbill and the rare Cornish heath which is only found on The Lizard. On the flattest parts of the peninsula underlain by serpentine, we find a fine quartz-rich windblown dust (loess) that was derived from the area now occupied by the Celtic Sea during the last cold phase of the Ice Age. Here we find acid-loving plants instead. Very few people know that the quarry (RIGS) by the BT's Goonhilly Earth Station is the reference section for loess in Cornwall.

There is a tremendous amount of variety between the farms and villages of individual Lizard parishes. Every village and farm is unique because men have always used the local rocks to construct their material worlds. For example, on the areas underlain by gabbro, the land had to be cleared of large boulders (core stones) to make fields. These ended up in the stone-faced Cornish hedges or in the walls of farmhouses. In places like Main Dale and Crousa Downs you can still see what the landscape would have looked like in the distant past. There are probably very few churches outside of the Lizard that can boast beautifully shaped and polished serpentine fonts, lecterns and bible stands.

Click here for a list of photograph credits

Granites | The Lizard | Killas | Coastline