Subsurface Mapping ( contour Maps and Cross Sections) Flashcards
Topographic maps
- Show highs and lows on the surface of the earth
- geomorphic feature and urban dev features (roads, transmission lines, buildings)
Slope
Slope= rise/run
= Elev/ Distance
Exploration Techs
Contour Mapping
Cross section Construction
Contour Mapping
Involves joining points of equal value together
- Isopach
- Elev Maps (topo maps and structural maps)
Isopach Maps
thickness of a subsurface foundation of a rx unit
range >= 0m
Elev maps
reference = sea level = 0m = 0ft
+ value - higher than sea level
-value - lower than sea level
Topo maps
Elev on the Earth surface
Structural maps
Elev on top of a subsurface foundation of a rx unit
Cross section construction
side view = vertical prohte x -s
included structural and stratigraphic cross section
rules of contouring
- choose a contour interval suitable
- Join points of equal value together
- contour lines must fall proportionally btw points of higher and lower values
- do not intersect or cross
- never split or merge in a Y-shape
- adjust the contours so that the gradient is gradual
- when contour lines cut across streams, they bend upstream
- when a slope reverses direction, such as across a ridge or a valey, the last contour most be repeated
rules of contouring 2
- on topo or structural maps, close contours indicate a hill or a ridge. closed contours with hasher indicate a closed depression, such as a pit or a lake
10 must not end on a map - beware of “edges effects”
- it is best to contour in bands of several contours
- numbered and labeled several places on the map
- key contours - heavy lines
- Value (0) of every map correctly, depending upon whether the map is topo or isopach map
Structural maps
- show highs and lows on the top of a formation in the subsurface
- Elev - sea level
- structure map on top of a gravel sandbar in the subsurface
upslope
upgradient = updip= anticline
downslope
downgradient = downdip=syncline
anticline
syncline
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