part 1
paleontologist
______________ speciallize in the study of fossils
saltation
a series of short leaps or bounces off the bottom
gradient
the downhil slope of the streams bed
headwater
usually a stream's gradient is greatest at its ___________
streams
what are one of the most effective sculptors of the land
valleys
what are the most common land form on the earth's surface
tectonic forces
what can cause the overturning or disruption of beds so much that the principle of superposition cannot be used
turbulance
what counteract gravity in saltation
uplift
what is a key factor in the formation of many incised meanders
urbanization
what is one cause of severe flooding
velocity
what is the key factor in a stream's ability to erode, transport and deposit
relative
_____________ time is the sequence in which events took place , rather than the number of years involved (geologist are more concerned with this number)
correlation
__________________usually means determining time equivalency of rock units (within a region, continent)
noncomformity
a _____________ is a contact in which an erosion surface on plutonic or metamorphic rock has been covered by younger sedimenary or volcanic rock (generally indicates deep or long erosion before subsequent burial)
stream
a body of running water that is confined in a channel and moves downhill under the influence of gravity
flood plain
a broad strip of land built up by sedimentation on either side of a stream channel
v-shaped
a cross section of a stream in steep mountains is usually what shape
alluvial fan
a large fan or cone shaped pile of sediment that usually forms where a stream's velocity decreases as it emerges from a narrow mountain canyon onto a flat plain
actualism
a principle that the same processes and natural laws operated in the past are those we can actually observe or infer from observations as operating in the present
divide
a ridge or strip of hight ground dividing one drainage basin from another
transporting overcoming
a river's energy is used for 2 thing ___________sediment and ___________ resistance to flow
tributary
a small stream flowing into a larger one
delta
a stream flowing through quiet waters usually builds a _________- a body of sediment deposited at the mouth of a river when the river's velocity decreases
key bed
a very distinctive layer can be used to correlate rocks over great distances (volcanic ash)
angular uncomformity
an __________________ is a contact in which younger strata overlie an erosion surface on tilted or folded layered rock (implies- deposition, lithofication, uplift, erosion)
formation
bodies of rock of considerable thickness with recognizable bodies characteristics that make each distiguishable from adjacent rock units (named after geographic features)
unconformities
contacts representing buried erosion surfaces-a surface or contact that represents a gap in the geoligic record with the rock layer above the contact being considerably younger than the rock beneath
unusual
correlation by rock type is more reliable if a very ____________sequece of rock or involved
numerical
dating based on radioactivity allows us to determine a rocks ___________ age (age given in units of time)
potholes
depressions that are eroded into the hard rock of a streambed by the abrasive action fo the sedimet load
dendritic
drainage pattern- acute angles- looks like branches of tree or nerves (formed on uniformly erodible rock)
discharge velocity
during floods a streams ___________ and ___________ increase
silt clay
flood deposits are usually ____________ and __________
reoccurance intervals
floods are described by_________________- the average time between floods of a given size
disconformity
in a ________________ the contact representing missing rock strata seperates beds that are parallell to one another (probably the older rock eroded away
uiformitarianism
james huttons concept that geologic operating at preset are the same processes that operated in the past eventually became known as teh principle of ______________ (the present is the key to the past)
natural levees
low ridges of flood-deposited sediment that form on either sid of a stream channel and thin away from the channel
lower
meandering is common in the ________________reaches of a river
traction
movement by rolling, sliding or dragging
absolute
numerical age is also known as _________age
runoff
only 15% TO 20 % of rainfall normall ends up as surface __________ in rivers
riprap
protective walls of stone or concrete constructed along river banks- particularly along curves
meanders
rivers that carry fine-granined silt and clay in suspension tend to be narrow and deep and to develop pronounced sinuous curves called _________
intrusive contact
rock which intruded after orginal rock layer was formed
dissolved load
soluble products of chemical weathering processes -ions
stream terraces
steplike landforms found above a stream and its flood plain
bar
stream deposits may take the form of a ___________- a ridge of sediment, usually sand and gravel, deposited in the middle or along banks of a stream- (formed when velocity or discharge decreases0
shape roughness
the ____________ and _________of a channel controls a streams velocity
hydraulic action
the ability of flowing water to pick up and move rock and sediment
drainage pattern
the arraingements, in a map view of a river and its tributaries
faunal succession
the discovery of william smith who realized that fossil species succeed one another through the layers in a predictable order
abrasion
the erosive process that is usually most effective on a rocky streambed is _______________
bed load
the large or heavy sediment particles tht travel on the stream bed - moved by traction or saltation
base level
the limit of downcutting: theoretical limite for erosion of the earth's surface
deposition
the low velocity on the inside of a river's curve promotes sedimnent ___________
sinking
the mississippi delta is ____________as upstream dams catch sediment, reducing the delta's supply
hydodrologic cycle
the movement and interchange of water between the sea, air and land
mouth
the place where a stream enters the sea, a lake, or a larger stream
inclusion
the principle of _______________ states that fragments included in a host rock are OLDER than the host rock
superposition
the principle of _______________ states that within a sequence of undistrubed sedimentary or volcanic rock, the layers get younger going from bottom to top
original horizantally
the principle of ____________________ states that beds of sediment deposited in water formed as horizantal or nearly horizantal layers
lateral continuity
the principle of _______________________ states that an original sedimentary layer extends laterally until it taper or thins at its edges
cross cutting relationships
the principle of ___________________________ states that a disrupted pattern is older than the cause of the dispruption
downcutting
the process of deepening a valley by erosion of the streambed
coarsest
the sediment near the river is _______________
point bar
the sediment on the inside of a curve the consists of a series of arcuate ridges of sand or gravel
suspended load
the sediment that is light enough to remain lifted indefinitely above the bottom by water turbulence
velocity
the streams ___________ is the distance water travels in the stream per unit of time (up to 15miles/hr)
stratigraphy
the subdiscipline in geography that uses interrelationships between layered rock or sediment to interpret the history of an area
contacts
the surfaces seperating 2 different rock types or rocks of different ages (used to decipher geological history)
contact metamorphosed
the tilted layers immediately adjacent to granite bodies are ____________________ a result of intrusion of hot granite magma
drainage basin
the total area drained by a stream and its tributaries
headwaters
the upper part of the stream near its source in the mountain
discharge
the volume of water that flows past a fiven point in a unit of time
fossils
these are common in sedimentary rock and their presence is important for correlation
placer
these types of deposits happen where running water has mechanically concentrated heavy sediment
sheetwash
thin layers of unchanneled water flowing downhill
trellis
this drainage pattern consists of parallel mainstreams with short tributaries meeting at right angles (forms in an area of titled layers of resistant rock)
rectangular
this drainage pattern has 90 degree angles- develops on regularly fractured rock
radial
this drainage pattern is where streams diverge outward like spoke of a wheel (forms on high conical mountains)
continental divide
this extends from the yukon to mexico and seperates drainage basin east and west
stream channel
this is where a stream normally stays- it is a long narrow depression eroded by the stream into rock or sediment
distributaries
this marks the surface of most deltas, - small shifting channels that carry water away from the main river channel and distribute it over the surface of the delta
foreset
this type of bed from the main body of the delta- they are depositied at an angle to the horizontal
topset
this type of bed is above a foreset and is nearly horizontal
bottomset
this type of bed is in from of a foreset bed - it is deposits of t he finest silts and clay
physical continuity
this type of correlation traces physically the course a rock unit
headward
this type of erosion allows a stream to lengthen its valley - it is the slow uphill growth of a valley above its orginal source through gullying - mass wasting and sheet erosion
lateral
this type of erosion is the erosion and undercutting of a streams banks and valley walals as the stream swings from side to side across its valley floor
flash
this type of flood is local, sudden with large volumes over a short duration-often triggered by heavy thunderstorms
incised
this type of meander retain their sinuous pattern as they are cut vertically downward below the level at which they orginally formed- result is no flood plain
graded
this type of stream is one that exhibits a delicate balance between its transporting capacity and the sediment load available to it
braided
this type of stream is typically shallow flows in a network of interconnecting streams
rills
tiny streams made from overland sheetwash
sediment
what might be deposited as velocity decreases
continental drift
what theory uses correlation of rock type as its proof
slot
what type of canyons are formed by downcutting
outside
when a stream goes around a curve- the region of maximum velocity is displace by inertia toward the ___________ of the curve
james hutton
who is regarded as the father of geology
charles lyell
who wrote the book Principles of Geology