The British Tertiary Volcanic Province was created 60-50 million years ago during the formation of the North Atlantic. As the Earth's crust stretched, volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

es and lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

 flows erupted along a line from Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 to the Hebrides

Hebrides

The Hebrides comprise a widespread and diverse archipelago off the west coast of Scotland. There are two main groups: the Inner and Outer Hebrides. These islands have a long history of occupation dating back to the Mesolithic and the culture of the residents has been affected by the successive...

. The Giant's Causeway

Giant's Causeway

The Giant's Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic eruption. It is located in County Antrim on the northeast coast of Northern Ireland, about three miles northeast of the town of Bushmills...

 and Staffa

Staffa

Staffa from the Old Norse for stave or pillar island, is an island of the Inner Hebrides in Argyll and Bute, Scotland. The Vikings gave it this name as its columnar basalt reminded them of their houses, which were built from vertically placed tree-logs....

 are the most famous natural monuments created by this event. Other sites include: Skye

Skye

Skye or the Isle of Skye is the largest and most northerly island in the Inner Hebrides of Scotland. The island's peninsulas radiate out from a mountainous centre dominated by the Cuillin hills...

, Mull

Isle of Mull

The Isle of Mull or simply Mull is the second largest island of the Inner Hebrides, off the west coast of Scotland in the council area of Argyll and Bute....

, Ardnamurchan

Ardnamurchan

Ardnamurchan is a peninsula in Lochaber, Highland, Scotland, noted for being very unspoilt and undisturbed. Its remoteness is accentuated by the main access route being a single track road for much of its length.-Geography:...

, Arran

Isle of Arran

Arran or the Isle of Arran is the largest island in the Firth of Clyde, Scotland, and with an area of is the seventh largest Scottish island. It is in the unitary council area of North Ayrshire and the 2001 census had a resident population of 5,058...

, Sanday

Sanday, Inner Hebrides

Sanday is one of the Small Isles, in the Scottish Inner Hebrides. It is a tidal island linked to its larger neighbor, Canna, via sandbanks at low tide, and also connected to the larger island by a bridge...

, Eigg

Eigg

Eigg is one of the Small Isles, in the Scottish Inner Hebrides. It lies to the south of the Skye and to the north of the Ardnamurchan peninsula. Eigg is long from north to south, and east to west. With an area of , it is the second largest of the Small Isles after Rùm.-Geography:The main...

, Canna

Canna, Scotland

Canna is the westernmost of the Small Isles archipelago, in the Scottish Inner Hebrides. It is linked to the neighbouring island of Sanday by a road and sandbanks at low tide. The island is long and wide...

, Rathlin Island

Rathlin Island

Rathlin Island is an island off the coast of County Antrim, and is the northernmost point of Northern Ireland. Rathlin is the only inhabited offshore island in Northern Ireland, with a rising population of now just over 100 people, and is the most northerly inhabited island off the Irish coast...

 and Lundy

Lundy

Lundy is the largest island in the Bristol Channel, lying off the coast of Devon, England, approximately one third of the distance across the channel between England and Wales. It measures about at its widest. Lundy gives its name to a British sea area and is one of the islands of England.As of...

. The dike

Dike (geology)

A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...

 complexes of the province contain many examples of dolerite

Diabase

Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. In North American usage, the term diabase refers to the fresh rock, whilst elsewhere the term dolerite is used for the fresh rock and diabase refers to altered material...

 dike swarm

Dike swarm

A dike swarm or dyke swarm is a large geological structure consisting of a major group of parallel, linear, or radially oriented dikes intruded within continental crust. They consist of several to hundreds of dikes emplaced more or less contemporaneously during a single intrusive event and are...

s.