Craven Fault System

File:Map-Aire Gap England.png]]

The Craven Faults are major crustal fractures across the Pennines. These faults constitute a zone crossing the backbone of England from west to east commencing near Leck, Lancashire at {{coord|54.190507|-2.527339|display=inline|region:GB_scale:20000}} then branching three ways:

• The North Craven Fault extends about {{convert|50|km|mi|-1}} to {{coord|54.074|-1.800|display=inline|region:GB_scale:20000}}.
• The Mid Craven Fault extends about {{convert|36|km|mi|-1}} to {{coord|54.070|-2.075|display=inline|region:GB_scale:20000}}.
• The South Craven Fault extends about {{convert|39|km|mi|-1}} to {{coord|54.066|-2.042|display=inline|region:GB_scale:20000}}.[http://www.bgs.ac.uk/products/digitalmaps/home.html] British Geological Survey, Geology of England and IOM, DiGMapGB625, data NERC 2008{{cite book |title=Geology of the Yorkshire Dales National Park |last= Wilson |first=Alfred |year=1992 |publisher=Yorkshire Dales National Park Committee |location=Grassington |isbn=0-905455-34-7|page=2}}

The Craven Gap is sometimes called the Aire Gap, but to do so necessitates including the Aire Fault; that runs from the south end of the South Craven Fault: from Gargrave towards Leeds. Although of less amplitude than the three Craven faults the course of the Aire Fault is made more apparent by the River Aire. The broad Aire Gap separates the Yorkshire Dales from the Bowland Fells and the Millstone Grit plateaux of the South Pennines.

File:Ingleton WTL.svg, Ingleton, below Quaternary terminal moraine at Raven Ray{{sfn|CPGS|2003|p=8}}]]

The fault system comprises the North Craven Fault, Middle Craven Fault, South Craven Fault and Feizor Fault along with various other unnamed faults. The Middle Craven Fault moved mainly during Carboniferous times and marks the southern limit of the Askrigg Block. However the North and South Craven faults continued to be active into post-Triassic times.{{rp|16}} The Great Scar Limestone is exposed north of the Middle Craven Fault at Malham Cove and at Gordale Scar{{cite book |title= Circular Walks Along the Pennine Way|last=Donkin |first= Kevin|year=2006 |publisher=Frances Lincoln Ltd |location= London|isbn=978-0-7112-2665-4}} and along the South Craven Fault at Giggleswick Scar.

[[File:Thrown fault blocks.jpg|thumb|left|A. Upthrown fault block;

B. Downthrown fault block;

1. Fault zone;

2. Steep face;

3. Gentle slope;

4. Valley filled with eroded surface runoff;

5. Sedimentary rock layers;

6. Bedrock;

7. Sedimentary rock layers worn away; these matched layers 5.]]

File:On the fault line^ - geograph.org.uk - 1175269.jpg

The Great Scar Limestone is over 200 metres thick and the overlying Yoredale Series was over 300 metres thick before weathering.{{cite book |title=The Yorkshire Dales: South and West|last=Kelsall|first= Dennis |first2=Jan |last2=Kelsall |year=2008 |publisher=Cicerone |location= Milnthorpe |isbn=978-1-85284-485-1}}{{rp|12}} The vertical throw of the fault zone is up to {{convert|1,800|m|ft|abbr=on|0}}.

Near Ingleton, North Yorkshire the North Craven Fault has a downthrow of about {{convert|200|m|ft}}, and a few hundred yards away the South Craven Fault has a downthrow of about {{convert|1200|m|ft}}.{{sfn|Waltham|2007|pages=54–57}} The fault plane of the North Craven Fault is exposed in Swilla Glen.{{sfn|Waltham|2007|page=91}}

Charles Darwin used the Craven Fault to illustrate how nature can so well conceal dramatic events: "The Craven Fault, for instance, extends for upwards of 30 miles, and along this line the vertical displacement of strata has varied from 600 to 3000 feet."{{cite book |title=On the Origin of Species |url=https://archive.org/details/in.ernet.dli.2015.93440 |last=Darwin |first=Charles |trans-chapter=XIV |chapter=On the Imperfection of the Geological Record}}

File:Giggleswick Scar - geograph.org.uk - 42107.jpg|Giggleswick Scar

File: Hillside above Settle and the Langcliffe mills - geograph.org.uk - 782271.jpg|View NW across Ribble to Giggleswick Scar

File:Warrendale Knotts - geograph.org.uk - 114740.jpg|Warrendale Knotts

File:Cross Field Knotts - geograph.org.uk - 1034650.jpg|Cross Field Knotts

{{Reflist}}

• {{cite web|url=http://www.ingletonwaterfallstrail.co.uk/assets/resources/files/geology.pdf|title=Ingleton Waterfalls trail|last=CPGS|year=2003|publisher=Craven and Pendle Geological Society|format=PDF|accessdate=5 March 2014|archive-date=12 May 2013|archive-url=https://web.archive.org/web/20130512210654/http://www.ingletonwaterfallstrail.co.uk/assets/resources/files/geology.pdf|url-status=dead}}

• {{cite book|last=Waltham|first=Tony|title=The Yorkshire Dales Landscape and Geology|date=2007|publisher=Crowood Press Ltd.|location=Marlborough|isbn=978-1-86126-972-0}}

• {{cite web |url=http://www.yorkshire-dales.com/craven-fault.html |title=The Craven Fault |publisher=www.yorkshire-dales.com |accessdate=2009-09-14 }}

Category:Geology of North Yorkshire

Category:Geology of the Pennines

Category:Geology of Lancashire