Volcanoes That Erupted Here in the the in Here Erupted That Volcanoes the by Formed Rocks

past. mineral grain. mineral and so has larger crystals than the basalt. the than crystals larger has so and rocks, formed by the volcanoes that erupted here in the the in here erupted that volcanoes the by formed rocks, of grains. Each individual patch of colour is a single single a is colour of patch individual Each grains. of Above: Bass Rock phonolite, which cooled relatively slowly slowly relatively cooled which phonolite, Rock Bass Above: coast is shaped this way because of the local igneous igneous local the of because way this shaped is coast are all taken at the same scale to show different sizes sizes different show to scale same the at taken all are of East Lothian, which juts out into the Firth of Forth. The The Forth. of Firth the into out juts which Lothian, East of These photos of thin sections from North Berwick Berwick North from sections thin of photos These On a larger scale, North Berwick lies at the northern edge edge northern the at lies Berwick North scale, larger a On easily. rock’s minerals and their shapes can be seen more more seen be can shapes their and minerals rock’s microscope and with light shone through them, the the them, through shone light with and microscope cut them into slices, called thin sections. Under the the Under sections. thin called slices, into them cut Geologists often take rocks back to the lab and and lab the to back rocks take often Geologists Rocks under the microscope the under Rocks Above: recent lava flow at Krafla in Iceland. in Krafla at flow lava recent Above: crystals that formed later. formed that crystals formed first and cooled more slowly than the many smaller smaller many the than slowly more cooled and first formed Above: Basalt from Lamb Island. The few larger crystals crystals larger few The Island. Lamb from Basalt Above: Seabird Centre, and also for a sheltered harbour. sheltered a for also and Centre, Seabird make a headland jutting out to sea. A great site for the the for site great A sea. to out jutting headland a make erupted around 345 million years ago. These lava flows flows lava These ago. years million 345 around erupted The Scottish Seabird Centre sits on top of lava flows that that flows lava of top on sits Centre Seabird Scottish The the islands offshore formed like this. like formed offshore islands the slowly, resulting in larger crystals and a tougher rock – – rock tougher a and crystals larger in resulting slowly, If magma gets trapped underground it will cool more more cool will it underground trapped gets magma If cools quickly and erupts from a volcano as lava or ash. ash. or lava as volcano a from erupts and quickly cools inside the Earth. If the magma reaches the surface it it surface the reaches magma the If Earth. the inside rocks start out as magma, hot molten liquid rising from from rising liquid molten hot magma, as out start rocks together and are difficult to break apart. All igneous igneous All apart. break to difficult are and together rock, called igneous rock, made of tiny crystals that lock lock that crystals tiny of made rock, igneous called rock, giving small crystals. small giving a key to understanding the distant past. distant the understanding to key a hard create Volcanoes volcano. extinct an of remains the of the three rocks shown here, this one cooled the fastest, fastest, the cooled one this here, shown rocks three the of Centre formed in the same way - the present provides provides present the - way same the in formed Centre is and town, the above steeply rises Law Berwick land. Above: Basalt from lava flow at North Berwick pier. Out Out pier. Berwick North at flow lava from Basalt Above: rock called basalt. The basalt layers under the Seabird Seabird the under layers basalt The basalt. called rock the of shape the in volcanoes for evidence of plenty Hawaii, the lava often cools to create a smooth, dark dark smooth, a create to cools often lava the Hawaii, see you’ll around, look a take and Centre Seabird the When a volcano erupts in places such as Iceland and and Iceland as such places in erupts volcano a When outside stand you If volcanoes? these are where So work out what happened in the past in Scotland. Scotland. in past the in happened what out work seabirds. for homes safe and anchorage world now to understand North Berwick’s rocks, and and rocks, Berwick’s North understand to now world safe a giving scenery, local the create to helping – today By using knowledge of what’s happening around the the around happening what’s of knowledge using By important is past the in happened what why out finding and texture. How can we work out how they formed? formed? they how out work we can How texture. and and volcanoes ancient these of parts different exploring made of different chemicals and with varying minerals minerals varying with and chemicals different of made shore, the along walk a on you takes leaflet This activity. information. There are many different kinds of rock, rock, of kinds different many are There information. volcanic intense of area an once was this that is know stories of the past – detectives working with limited limited with working detectives – past the of stories not may you What Law. Berwick hill, prominent its and In studying rocks, geologists are trying to unravel the the unravel to trying are geologists rocks, studying In islands offshore seabirds, its for known is Berwick North Rocks as clues to the past the to clues as Rocks Introduction Islands visible from the shore How to get there North Berwick North Berwick, 25 miles east of Edinburgh, is easily accessible by train, bus or car. For details of public transport contact Traveline on 0800 608 2 608 or Volcanoes visit www.traveline.org.uk. This leaflet describes a walk eastwards along the shore from the Scottish Seabird Centre at North Berwick harbour, close to the town centre. The Seabird Centre is well sign- posted. There’s plenty of free parking nearby, both along the beach and at car parks in the town. There The offshore islands are all composed of igneous are public toilets at the Seabird Centre (inside and Geological Walk rocks formed as molten rock (magma) cools and out) and at the Melbourne Place car park. hardens underground. They are called intrusions, Safety and conservation unlike most of the rocks seen on the shore which The beach is accessible at all states of the tide but were formed at the surface as volcanic extrusions. some of the features are covered at high tide. You There’s been lots of erosion to allow us to see these should be aware that the shore is slippery and has rocks that formed beneath the surface. Intrusive loose materials, with the risk of tripping, slipping rocks forming under volcanoes today might not be and falling. North Berwick shore is part of a Site of seen for millions of Special Scientific Interest because of its geology years. and hammering of the rocks is not encouraged. Bass Rock and Acknowledgements Berwick Law Text & images: Neil van Beinum, University of are made of an Edinburgh, Angus Miller, Scottish Earth Science unusual rock Education Forum, Colin Souness, Our Dynamic called phonolite, a Earth. Designed by Derek Munn. “sounding stone”, so called because Produced by the Lothian and Borders RIGS Group it makes a metallic of the Edinburgh Geological Society, a charity noise if hit with a hammer. If you get up close to registered in Scotland Charity No: SC008011 the rock, it appears lighter in colour and has larger © 2010 Lothian & Borders RIGS Group crystals which cooled more slowly than the basalt. These big masses of rock are ancient plugs, bodies [email protected] www.edinburghgeolsoc.org of magma that solidified in the neck of a volcano. Local Geodiversity Site Craigleith is lower with sloping sides, and is an example of a laccolith, a mushroom-shaped body of magma that has intruded into surrounding layers of rock and cooled. Lothian and Fidra and Lamb can be seen farther to the west. They are part of another intrusion forming a sheet Borders of basalt rock called a sill. RIGS Group Mapwork based on Ordnance Survey Licence number 100033582 The red rocks formed in a very different way than the basalt, when volcanic ash was erupted and settled into layers that were slowly turned to rock. It is known as tuff. Partan Craig (volcanic vent) Limestone The red layers lie underneath the lava, and they tell us The Yellow Craig Rock that before the lava flows erupted, the volcano was very Red Volcanic Ash (dyke intrusion) active. Green Volcanic Ash Time after time, showers of ash and rock fragments were Volcanic Vent Agglomerate blasted into the sky. This probably happened because Basalt Lava there was lots of water around: magma and water make an explosive mix. Stop 3: The Yellow Craig Rock The walk along the shore takes you through the crystals are tiny and best seen using a microscope (see A short walk along the beach to the east will take you to different parts of ancient volcanoes. We’ll walk back pictures overleaf). the Yellow Craig Rock, a lone cliff that protrudes out of through time, down through the layers that used to be This rock is called basalt, and it formed as part of a lava the sand like a ship’s keel.

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