Ullapool bolide impact
Encyclopedia
Evidence for a bolide impact centered on Ullapool was published by a combined team of scientists from the University of Oxford
and the University of Aberdeen
, in March 2008. The evidence is centred on Ullapool
, a harbour town on Loch Broom
in the Ross and Cromarty
district of the Highland
council area of northwest Scotland
. This suggests it was the largest bolide impact ever to strike what are now the British Isles
. The impact, which has been dated to 1177±5 million years ago, melted rock at the site and left parallel shock fractures in quartz
and biotite
and a tell-tale trace of iridium
. Centered on the impact crater
, a wide ejecta field
has been traced, some 50 km across, forming the Stac Fada member within the Stoer Group of the Torridonian
. The affected layer of rock, which on land stretches from Gairloch
in the south to Stoer
in the north is six to 22 metres thick. Until recently, these anomalous formations were unsatisfactorily credited to an isolated instance of volcanism
.
The crater, preserved under sedimentary layers of sandstone
, is currently presumed to lie under the Minch, the waterway that separates the Isle of Lewis in the Outer Hebrides
from the north-west Highlands of Scotland. It has been estimated that the impact would have created a blast with the force of 145,000 megatons
and that the shock wave would have created winds of 420 km/h as far away as the site of modern Aberdeen
.
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...
and the University of Aberdeen
University of Aberdeen
The University of Aberdeen, an ancient university founded in 1495, in Aberdeen, Scotland, is a British university. It is the third oldest university in Scotland, and the fifth oldest in the United Kingdom and wider English-speaking world...
, in March 2008. The evidence is centred on Ullapool
Ullapool
Ullapool is a small town of around 1,300 inhabitants in Ross and Cromarty, Highland, Scotland. Despite its small size, it is the largest settlement for many miles around, and is a major tourist destination of Scotland. The North Atlantic Drift passes by Ullapool, bringing moderate temperatures...
, a harbour town on Loch Broom
Loch Broom
Loch Broom is a sea loch located in northwestern Ross and Cromarty, in the former parish of Lochbroom, in the west coast of Scotland. The small town of Ullapool lies on the eastern shore of the loch...
in the Ross and Cromarty
Ross and Cromarty
Ross and Cromarty is a variously defined area in the Highlands and Islands of Scotland. There is a registration county and a lieutenancy area in current use...
district of the Highland
Highland (council area)
Highland is a council area in the Scottish Highlands and is the largest local government area in both Scotland and the United Kingdom as a whole. It shares borders with the council areas of Moray, Aberdeenshire, Perth and Kinross, and Argyll and Bute. Their councils, and those of Angus and...
council area of northwest Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
. This suggests it was the largest bolide impact ever to strike what are now the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
. The impact, which has been dated to 1177±5 million years ago, melted rock at the site and left parallel shock fractures in quartz
Shocked quartz
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure , the crystalline structure of quartz will be deformed along planes inside the crystal...
and biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
and a tell-tale trace of iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
. Centered on the impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
, a wide ejecta field
Ejecta
Ejecta can mean:*In volcanology, particles that came out of a volcanic vent, traveled through the air or under water, and fell back on the ground surface or on the ocean floor...
has been traced, some 50 km across, forming the Stac Fada member within the Stoer Group of the Torridonian
Torridonian
In geology, Torridonian describes a series of Neoproterozoic arenaceous sedimentary rocks, extensively developed in the Northwest Highlands of Scotland, and particularly in the district of upper Loch Torridon, a circumstance which suggested the name Torridon Sandstone, first applied to these rocks...
. The affected layer of rock, which on land stretches from Gairloch
Gairloch
Gairloch is a village, civil parish and community on the shores of Loch Gairloch on the northwest coast of Scotland. A popular tourist destination in the summer months, Gairloch has a golf course, a small museum, several hotels, a community centre, a leisure centre with sports facilities, a local...
in the south to Stoer
Stoer
Stoer is a crofting township in the parish of Assynt, Sutherland, in the Highlands of Scotland and in the council area of Highland. It is located about five miles north of the village of Lochinver....
in the north is six to 22 metres thick. Until recently, these anomalous formations were unsatisfactorily credited to an isolated instance of volcanism
Volcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....
.
The crater, preserved under sedimentary layers of sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
, is currently presumed to lie under the Minch, the waterway that separates the Isle of Lewis in the Outer Hebrides
Outer Hebrides
The Outer Hebrides also known as the Western Isles and the Long Island, is an island chain off the west coast of Scotland. The islands are geographically contiguous with Comhairle nan Eilean Siar, one of the 32 unitary council areas of Scotland...
from the north-west Highlands of Scotland. It has been estimated that the impact would have created a blast with the force of 145,000 megatons
TNT equivalent
TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...
and that the shock wave would have created winds of 420 km/h as far away as the site of modern Aberdeen
Aberdeen
Aberdeen is Scotland's third most populous city, one of Scotland's 32 local government council areas and the United Kingdom's 25th most populous city, with an official population estimate of ....
.
See also
- Silverpit craterSilverpit craterSilverpit crater is a buried sub-sea structure under the North Sea off the coast of the United Kingdom. The crater-like form, named after the Silver Pit — a nearby sea-floor valley recognized by generations of fishermen — was discovered during the routine analysis of seismic data collected during...
, the only other proposed impact crater in or near the British Isles. - Impact eventImpact eventAn impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant...
- List of impact craters on Earth
- North West Highlands GeoparkNorth West Highlands GeoparkThe North West Highlands Geopark is a geopark in the Scottish Highlands. Awarded UNESCO geopark status in 2004, it features some of the oldest rocks in Europe, around 3,000 million years old...
- Geology of ScotlandGeology of ScotlandThe geology of Scotland is unusually varied for a country of its size, with a large number of differing geological features. There are three main geographical sub-divisions: the Highlands and Islands is a diverse area which lies to the north and west of the Highland Boundary Fault; the Central...