Snowdon (Yr Wyddfa), Gwynedd (National Trust): photo © Mick Sharp

This is the view south-eastwards from our garden, if you are over seven feet tall and have telescopic vision. The Great Tomb (or Throne) rises above the other mountain tops of the Snowdonia National Park whose ancient name is Eryri or ‘The Highland’. Snowdon is the highest mountain in England and Wales, its peak soaring 3,560 feet (1,085m) above sea level, which is where parts of it started out in the Cambrian period over 500 million years ago. Sediments from the seabed were subjected to great pressure, and metamorphosed by volcanic action into slates and grits. Earthquakes and eruptions lifted, folded and distorted the layers, and covered them in new rocks made from lava and ash. Some of the deposits at Snowdon’s summit still bear the marine fossils of their youth. To finish the effect, glaciers carved out and smoothed Nant Gwynant and other U-shaped valleys, leaving hanging tributary valleys or cwms, some with spectacular waterfalls. The glaciers also redistributed boulder clay and gravel debris, and cut the dizzying knife-edge ridges of ‘arêtes’ such as Crib Goch. Alpine flora and legends have lodged in the crevices and thin acid soils of this grand geology lesson: King Arthur fought the giant Rhita Gawr here, and on the adjacent peak of Y Lliwedd, his knights lie sleeping in a magically sealed cave, waiting to be awoken and set free.

Liathach, Glen Torridon, Ross and Cromarty, Highland (NTS): photo © Jean Williamson

Snow in May still clings to the red Torridonian sandstone ridge of Liathach, whose central, pyramidal summit, Spidean a’ Choire Léith, reaches to 3,456ft (1,053m). In the Precambrian era before plants existed, Glen Torridon was situated in the southern hemisphere: some of its rocks are amongst the oldest in the world. One thousand million years ago it was part of the wandering continent of Laurentia which now forms much of Greenland, Canada and the USA. Pebbles, sand and mud were carried away from its mountains by huge river systems to be deposited on a vast barren plain of already old Lewisian gneiss. The plain’s valleys and low hills were eventually covered by a mass of sediments over four miles (7km) thick, which became the red and chocolate sandstones of the Torridon group in north-west Scotland. Erosion by wind, water and the glaciers of several Ice Ages removed most of this soft coating back down to the Lewisian gneiss, but in places the banded sandstone was protected by harder caps of pale grey Cambrian-period quartzite. These preserved, isolated eminences such as Liathach are known as ‘Inselbergs’ or island mountains. In the presence of these ancient forms, we can begin to be conscious of the immensity of time over which the earth has been recycling itself.

The Cheesewring, Bodmin Moor, Cornwall: photo © Jean Williamson

When magma - molten rock from the earth’s mantle - reaches the surface, it becomes lava whose cooling flows form basalt and other volcanic rocks. If the magma forms rock masses within the earth’s crust these are called igneous intrusions, granite being the most common. Water penetrated the chinks and joints of the granite, expanded on freezing and began to break up the stone. During a tropical period, water was able to penetrate metres into the rock bed to attack micas and feldspars by chemical weathering and bring about ‘deep-rotting’ of the granite. Eventually the softened stone disintegrated to reveal ‘core-stones’ of harder granite, which were then further stripped and shaped during another cold period. The results of all this determined work can be seen in the weather-sculpted granite rock-stacks of Dartmoor and Bodmin Moor. The defended settlement of Stowes Pound occupies much of the Cheesewring’s hill, and a smaller, pear-shaped enclosure takes in several of the rock stacks on the summit. This may have been a Neolithic ritual space to the natural forces: it is not unusual to still encounter someone welcoming the dawn, or bidding the sun goodnight, from these natural platforms. Daniel Gumb, the 18th-century stonecutter and memorial mason, made a home for himself and his family by excavating a rock shelter here. His cave has been quarried away, but its porch of large stones survives. Gumb used to lie on its roof slab to look at the stars, and he carved a Euclidean geometry problem into its upper surface.

Bryn Alyn Limestone Pavement, Eryrys, Denbighshire: photo © Jean Williamson

During the Carboniferous period of the Upper Palaeozoic era, some 350 million years ago, corals, sea-lilies (crinoids), brachiopods and other primitive marine invertebrates luxuriated in the clear, warm waters of shallow seas. They lived and died in their billions and billions, their shells of calcium carbonate littering the sea beds, building up thick deposits which became limestones. Earth movements lifted some of them to form ‘mountain limestone’ in areas such as the Mendips, Yorkshire and the Clwydian Hills. In places, well-jointed limestone was exposed to rainwater made acid by atmospheric carbon-dioxide which began to dissolve the rock along its joints. This resulted in a criss-cross pattern of deep clefts or ‘grykes’ dividing a pavement of limestone blocks or ‘clints’. Small plants and grasses thrive in the shelter of the channels while thorn-trees on the surface are bent and stunted by the wind. Bryn Alyn is a precious and protected Site of Special Scientific Interest (SSSI), an ‘international treasure’ within the Clwydian Range Area of Outstanding Natural Beauty (AONB).

Yr Eifl, Lleyn Peninsula, Gwynedd: photo © Mick Sharp

Bell heather (erica cinerea) cloaks the lower slopes of Yr Eifl’s central summit, its purple flowers vibrant against the pale grey scree. The triple hills - the Forks or Strides, known in English as ‘the Rivals’ - are made up of granite and other volcanic rocks, their peaks shaped by glacial action which has left the slopes covered by vast skirts of debris. After taking this photograph, we walked to the summit at 1,850ft (546m) to find a grey squirrel sitting on top of the Ordnance Survey triangulation pillar and marking its territory.

Uig Sands, Isle of Lewis, Western Isles: photo © Jean Williamson

Traigh Uige is an achingly beautiful, wide sandy bay on the west coast of Lewis, cut through by the winding channel of the Lòn Erista river as it makes a final sprint for the sea. As the sharply defined patterns in the sand suggest, at high tide the salt water will sweep in and wash away those impertinent footprints.

Kilpheder Beach and Dunes, South Uist, Western Isles: photo © Mick Sharp

Further down the western seaboard of the Outer Hebrides or ‘Long Island’, a silver-white beach shows up the brooding sky, the wind whitens the surf and moves amongst the plants of shore and dune: silverweed, meadow buttercup, birdsfoot trefoil, pyramid orchid and sea rocket. Excavated remains of a Pictish wheelhouse rest in the dunes, and on the adjacent, shell-rich ‘machair’ pasture a good crop of potatoes was growing amongst the grasses and wild flowers.

Pendour Cove, Zennor, Cornwall (National Trust): photo © Jean Williamson

Pendour is typical of the rocky headlands and small sandy coves of the north coast of West Penwith. According to local legend, a beautiful young woman in a long dress used to sit at the back of Zennor church, entranced by the voice of chorister Matthew Trewhella. One evening, she persuaded him to enter the village stream and led him out into the sea at Pendour Cove where, on a warm summer’s night, the mermaid and her human lover may be heard singing together.

Llanrhidian Marsh, The Gower, Swansea (NT/CCW): photo © Jean Williamson

One of the best examples of a salt-marsh in Britain has built up on silts in the Burry Inlet, or Pill, on the north coast of the Gower peninsula. A ‘high salt-marsh’ extending far in front of the old fossil limestone cliff-line, but inundated by only the very highest tides. The marsh is common land, used for the grazing of sheep and ponies, and internationally important for its huge populations of over-wintering wildlife. It is a distinct landscape of outstanding beauty within a designated Area of Outstanding Natural Beauty.

Burgh Castle Reach and Marshes, Great Yarmouth, Norfolk: photo © Jean Williamson

The River Yare rises to the west between Swaffham and Norwich, passes through that fine medieval city and flows to the North Sea at Great Yarmouth. In the mud and sand of Burgh Castle Reach, the rivers Waveney and Yare merge to form Breydon Water where the salty tide comes inland to greet them. To our right are the remains of the Roman fort of ‘Gariannonum’, to the left Berney Arms where a windmill water-pump of the late 1800s is still in working order. This watery world of reeds, tidal marshes, channels and mud-flats is on the eastern boundary of The Broads National Park set up in 1989. The system of broad, shallow lakes linked by rivers and other navigable channels was once thought to have formed after glacial action, but are now considered to be the result of human removal of peat and turf. Reeds are still harvested in the area and used by thatchers to create traditionally-patterned roofs.

Devil’s Gorge, Pantymwyn, Flintshire: photo © Jean Williamson

The River Alyn (Alun) flows northwards from the Clwydian Hills before turning south-eastwards at Rhydymwyn to join the Dee between Chester and Wrexham. Travelling through a limestone landscape of steep gorges and swallow holes, downstream of Loggerheads Country Park the Alyn disappears underground during summer dry spells, leaving its rocky bed exposed. The waters of the Alyn proved a boon and a bane for the owners of the lead, zinc and calcite mines along its course: as the underground workings expanded, so did the problems of flooding. A system of leats and waterwheels was set up to use the river to power the pumps removing its own water from the mines. In 1824, to power his mine-workings and overcome the periodic disappearances of the stream, John Taylor dug a channel to carry a reliable flow of water northwards from Loggerheads to his mine at Pen-y-fron. His leat, running along the eastern bank of the river, has become the Leete Path riverside walk. Amongst others, Taylor was visited by Felix Mendelssohn and Charles Kingsley whose works, ‘The Rivulet’ and ‘The Water Babies’, were influenced by the limestone stream and its man-made shadow.

Pant y Llyn Turlough, Gwenlais Valley, Carmarthenshire (Tarmac Ltd/CCW): photo © Jean Williamson

Like the Alyn, the waters of this turlough or ephemeral lake come and go thanks to the surrounding geology. With no inlet, it is fed from below through the underlying limestone, typically filling during autumn and winter to dry out again in summer. The only known example in mainland Britain, seasonal lakes are more common in Ireland from where the name ‘turloch’ or dry lake comes. Pant y Llyn supports an unusual variety of specialist aquatic plants and animals, and is surrounded by a range of special habitats including ancient woodland, grassland, heath, bog and disused limestone quarries. The proposals by MacAlpine to resume quarrying in the early 1990s led to fears that the lake would be destroyed by the new workings affecting the subterranean water-table. The hard-fought Campaign for the Protection of the Gwenlais Valley was largely successful: Tarmac Ltd own the land, but the area is part of the Cernydd Carmel SSSI (Site of Special Scientific Interest) and SAC (Special Area of Conservation). Pant y Llyn is part of the Carmel Reserve, managed by the Countryside Council for Wales and the Grassland Trust.