Geo Lab 7 (Geologic Maps)

formation

mappable body of rock

contacts

distinct boundaries

outcrops

exposures of bedrock

angular unconformity

nonparallel graphs in rocks above and below the unconformity

nonconformities

separate non bedded, crystalline rocks from younger sedimentary rocks

plutons

bodies of intrusive igneous rock

dikes

thin, tabular intrusions that cut across bedding (discordant)

sills

the other tabular intrusions, are concordant

crater

small depression at the top

calderas

large depression at the top

lava (or pyroclastic) flows

gas charged flows that produce tuff

geologic cross sections

like topographic profiles, but with the subsurface geology shown schematically

line of section

the line along which the cross section will be made

Rule of V’s

where a contact line crosses a valley, it forms a V that points in the direction of the dip of the contact between the two formations