Geology pt. 2
Terms
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- anticline
- an upward bend or fold in a rock layer
- gradient
- slope of stream channel along selected length of course
- runoff
- water flows over surface; rainfall exceeds soils ability to absorb rain
- hydrograph
- graph of a water body's discharge
- Law of Superposition
- The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.
- cutbank
- erosion on outer edge of meander
- streams that flow discontinuously
- intermittent
- head
- stream's origin (starts at highest elevation)
- strike slip fault
- Break in rock caused by shear forces where rocks slide past each other without much vertical movement
- normal fault
- an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall
- geologic map
- representation of a region showing earth information such as mineral deposits, fossil localities, age relations of rock units
- Cape Fear drainage basin
- the only drainage basin completely contained in North Carolina
- mouth
- end of a stream where it enters a lake, sea, etc.
- graphic bar scale
- "ruler" for measuring distances on a map
- dome
- a raised area shaped rouphly like the top half of a sphere often formed by magma pushing upward on the rock layers above it; rock is oldest at the center
- base line
- east and west line
- thrust fault
- a reverse fault where the hanging wall slides over the top of the foot wall
- basin
- an area of land largely enclosed by higher land; youngest rock is in the center
- principal meridian
- A north-south line
- point bar
- deposits accumulate along the inner edge of meander
- bankful stage
- water level is even with the top of the river bank
- base level
- lowest level that a stream can theoretically erode
- bearing
- the direction or path along which something moves or along which it lies
- radial
- develop around circular hills; volcanoes
- geologic cross section
- A diagram showing the geologic features that would be visible if vertical slices were made through part of the crust.
- infiltration
- water works into ground and percolates downward
- Law of Lateral Continuity
- An original layer extends laterally in all directions until it tapers or thins at the edges. Know that rocks were originally continuous.
- fractional scale
- A way of representing scale on a map with a fraction or ratio. Eg: 1/24,000 or 1:24,000 The left handed side represents distance on the map. The right handed side represents distance on the Earth.
- footwall
- The block of rock that forms the lower half of a fault.
- dendritic
- tree-like; develops in areas underlain by homogenous underlying rock
- strike
- the compass bearing of a line formed by the intersection of a horizontal plane and an inclined layer of rock, fault, fracture, or other surface
- relief
- the difference in elevation between the highest and lowest points in an area
- angular unconformity
- an unconformity in which younger sediment or sedimentary rocks rest on the eroded surface of tilted or folded older rocks
- monocline
- a geological formation in which all strata are inclined in the same direction
- syncline
- a downward bend or fold in a rock layer
- Law of Original Horizontality
- in a sequence of sedimentary rocks, layers of rock were originally formed lying horizontally
- attitude
- orientation of a rock unit or surface
- annular
- concentric rings in basins and domes
- load
- amount of sediment transported
- deltas
- river-, wave-, tidal-dominated
- contour lines
- lines that show elevation, relief and slope on a topographic map
- flood frequency
- stream discharge (Q=VxA) readings over time are collected to determine the frequency of discharge or stage; this determines the recurrence interval of different magnitude floods
- index contours
- labeled with the elevation in round units; thick, dark contour line
- verbal scale
- description of scale using words "one inch equal four miles"
- disconformity
- two parallel adjacent sedimentary layers that are of substantially different age
- trellis
- main stream intersected at nearly right angles to tributaries; form in ridges and valleys
- declination
- difference between true north and magnetic north
- recurrence interval
- (# of years + 1)/rank of event
- streams that flow permanently
- perennial
- contour interval
- This is the vertical distance between adjacent contour lines.
- structural mitigation
- dams, retention basins, channelization, artificial levees, raising structure
- relative dating
- Dating technique, for example, stratigraphy, that establishes a time frame in relation to other strata or materials, rather than absolute dates in numbers. (and rule of superposition)
- distributary
- opposite of dendritic, occur when stream approaches mouth; delta areas
- normal stage
- water level is below the river bank; established over time
- absolute dating
- determines actual age. fossil's near by rock contains radioactive elements that break down (decay) into different elements over time. half life of these elements means the time it takes for half of the atoms to decay they compare how much of the radioactive element is in the sample and the amount of the new element, then calculate the age.
- flood stage
- water level tops the bank
- floodplain
- the flat land that surrounds a stream and becomes submerged when the stream overflows its banks
- Law of Unconformities
- a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
- meandering stream
- usually occur in downstream areas where gradient is low, discharge and load are moderate to high, large floodplains develop, and a sinuous channel forms
- Law of Cross-Cutting
- any feature that cuts across a rock or body of sediment must be younger than t he rock or sediment that it cuts across
- reverse fault
- A fault in which the hanging wall moves up relative to the foot wall
- topographic map
- A representation of a region on a sufficient scale to show detail, selected man-made and natural features of a portion of the land surface including its relief and certain physical and cultural features; the portrayal of the position, relation, size, shape and elevation of the area
- straight stream
- rare except for short stretches or when rock dictates
- gradient
- a graded change in the magnitude of some physical quantity or dimension
- nonconformity
- a type of unconformity in which layered sedimentary rocks lie on an erosion surface cut into igneous or metamorphic rocks
- hanging wall
- The block of rock above a fault.
- non-structural mitigation
- buffer zones, wetlands, buyouts
- oxbow lake
- cut off a meander bend leaving the meander scar
- braided stream
- high discharge, sediment-loaded stream in in low to moderate gradient
- rectangular
- network of interconnected rectangles and squares; develops over fractured/faulted rock
- dip
- angle between the out crop and a horizontal plane
- Law of Inclusions
- a piece of one rock unit contained within another; inclusions are used in relative dating; the rock mass adjacent to the one containing the inclusion must have been there first in order to provide the fragment