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A2 Geology Maps (Geological Maps (Shows outcrop pattern of rocks across…
A2 Geology Maps
Geological Maps
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Different rocks and superficial deposits are distinguished by different colours, while range of symbols are used to represent various structures
Maps used are produced by British Geological Survey= standard OS maps as base and geological information superimposed on top, 3 variants=
- solid: only show outcrop of pre-Quaternary sedimentary, igneous, metamorphic rock
- Drift: distribution of unconsolidated Quaternary deposits such as alluvium, till, head and peat
- Solid and Drift: both materials shown
Scale: published at different scales, 1:25000 or 1:50000
Grid Lines: Use same system as OS maps, 4 or 6 grid references, Vertical= Eastings, Horizontal= Northings, 1km between grid lines, 1:50000= 2cm apart, 1:25000= 4cm apart
Geological column: gives information about type, age, thickness of rocks exposed on map, arranged so oldest at base on right side, vertical scale usually given at top and is normally 1cm to 100cm, information presented can be used to reconstruct changing environmental conditions and geological history of the area
Describing outcrops
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(b) Location, grid references, directions, grid squares containing outcrop
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Faults
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Seen as line, difficult to see if revers or normal
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Igneous intrusions
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Dip angle, pluton position and presence of water can affect size of metamorphic aurole
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Rock structure, outcrop patterns, surface topography
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Basin and Domes
Dome: Elliptical or circular anticline, pips away from centre
Basin: Elliptical or circular syncline, dips towards centre
Unconformity
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Identified by=
- Irregular erosional boundary
- Change in rock age identified by fossils
- Structure of rock doesn't match above and below
- Included fragments or rocks below in rocks above
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