Islands and sea loughs

Islands might have the appearance of tranquil havens, but in the beginning they were the explosive creations of turmoil on, and deep below, the Earth's crust.

Islands form for many reasons: sea levels dropping, volcanic activity under the sea bed pushing new rock to the surface, even tilting and folding of sedimentary rocks laid down many millions of years ago.

The Farne Islands, Northumberland

The Farnes, a series of 31 islands, are formed of particularly hard igneous or volcanic rock called Whin Sill. The Whin Sill has ‘out-cropped’ inland, and on other sections of the coast it has eroded back to low hard cliffs with large pebble beaches in more sheltered areas such as the cliffs at Dunstanburgh Castle.

Rathlin Island, Co Antrim

Rathlin Island, about 10 miles off the coast of North Antrim, is formed of another hard rock type, basalt.

Brownsea Island, Dorset

Brownsea Island is made up of softer sands, clays and pebbles washed out from the last ice sheet. It is in a sheltered location but is vulnerable to erosion and flooding when the wind is in an easterly direction. Large waves can reach the island through the entrance to Poole Harbour and easily wash away the soft cliffs.

Sea loughs

Where landscapes have been ‘drowned’, probably from rising sea levels, inland seas called sea loughs can form.

Strangford Lough, Co Down

Strangford Lough is the UK's largest sea inlet with over 120 islands dotted across it. It is a particularly rich area with clean shallow water that rushes in and out through a narrow entrance each tide.

The National Trust

Islands and sea loughs