WJEC A2 Geology BGS Mapwork I.G.Kenyon

BGS 1: scale maps 1mm on the map represents 50m on the ground Grid squares are 1 km² and have sides of 2cm on the map

BGS 1:25,000 scale maps 1mm on the map represents 25m on the ground Grid squares are 1 km² and have sides of 4cm on the map

BGS Maps are produced in solid and solid and drift editions Solid maps show only the fully lithified rocks Solid and drift maps show the lithified rocks plus any recent sediments deposited on top

Solid Geology – Cockermouth Sheet 23 1: Recent drift deposits such as alluvium and boulder clay not shown Carboniferous rocks Permo-Triassic Rocks

Solid and Drift Geology – Clitheroe Sheet 68 1:50,000 Alluvium River Terrace Deposits Solid Geology

Structures to Identify on BGS Maps 1 Beds – direction of dip/angle of dip Beds – strike direction/orientation Anticlines/synclines/monoclines Fold axes/axial plane of folds Domes/basins Symmetrical/asymmetrical folds Plunging folds Open/tight/recumbent/overturned folds

Structures to Identify on BGS Maps 2 Normal faults/reverse faults/thrust faults Tear faults – sinistral/dextral/step faults Graben/rift valley/Horst/block mountain Unconformities-angular/parallel/heterolithic Inliers/outliers Lava flow/sill/dyke/pluton/mineral veins Metamorphic aureole Inverted relief

Symbols on BGS Maps 1

Drift Symbols on BGS Maps

Generalized vertical sections are given on BGS Maps This is a vertical log of all the rock types present in chronological order with the oldest at the base and the youngest at the top On 1:50,000 maps the scale is often 1:10,000 On 1:25,000 maps the scale is often 1:4,000 However scales can vary-check carefully on each map that you are studying

Part of generalized vertical section from Cheddar Sheet ST45 1:25,000

Part of the generalized vertical section from Hawes Solid and Drift 1:50,000 Note that rock types and ages of beds are given Unconformities are clearly indicated in the section It is vital that the vertical section is studied carefully in conjunction with the map in order to interpret all of the geological structures

Cross sections are also included on BGS maps and should be studied carefully along with the vertical section and map From Hawes Solid and Drift 1:50,000 You do not have to construct cross sections from BGS maps at A2!

In addition to geological structures, you will be asked questions with a GL3 bias These could include evaluating the suitability of certain locations for the construction of roads, landfill sites, housing estates, reservoirs, power stations, dams or tunnels Questions relating to the causes of landslips are also a possibility

Sometimes additional maps are included on the BGS geology maps These may include magnetic, gravity, radon, isostatic or mineralogical data Questions related to this additional data may be asked in relation to the geological map

Okehampton/Dartmoor Map Geology and Gravity Anomalies Gravity anomalies (contoured in milligals). The negative gravity anomaly is due to the granite being of lower density than the surrounding rocks

Okehampton/Dartmoor Map Geology and Magnetic Anomalies Aeromagnetic anomalies (contoured in nanoteslas) Magnetic disturbances skirting the granite are due to mineralisation in the Lower Carboniferous rocks and basic intrusions at depth

The End Ash deposits of the Las Canadas Volcano, Tenerife, Canary Islands