91 terms

Science Ch. 6- Running Water and Groundwater

*Chapter Overview* -Running Water -The Work of Streams -Water Beneath the Surface
the movement of surface water into rock or soil through cracks and pore spaces
provides the most important link b/t the oceans & the land
the atmosphere
the avg. annual precip. over Earth = the amount of H2O that evaporates
Balance in the water cycle
the ability of a stream to erode & transport materials depends largely on its
the distance that H2O travels in a period of time
along straight stretches, the highest velocities are near the ______ of the channel just below the surface
the center of the channel is where friction is _______ (lowest or highest)
a stream's zone of max. speed shifts toward ___ ______ ____ when a stream curves
its outer bank
a stream's gradient, shape, size, & roughness of its channel are all factors that determine the ________ of a stream
the slope or steepness of a stream channel
usually expressed as the vertical drop of a stream over a certain distance
portions of the Mississippi River have very low gradients of __cm per km or less
the _______ the gradient, the more energy the stream has as it flows downhill
the course that the water in a stream follows
stream channel
shape, size, & roughness of the channel affect the amount of ______
the volume of H2O flowing past a certain point in a given unit of time
the discharge of most rivers change with
rainfall & snowmelt
when the discharge changes, so do the ____ & ________ of the stream
size & velocity
as the size of the channel __________, (increases or decreases) there is less friction & the H2O flows more swiftly
while gradient decreases b/t a stream's headwaters & mouth, _________ increases
a stream that empties into another stream
the lowest point to which a stream can erode its channel; the level at which the mouth of a stream enters the ocean, lake, or another stream
base level
the ultimate base level
sea level
a bend in the course of a stream; a stream in a broad, flat-bottomed valley that is near its base level often develops a course w/ many bends called
if base level dropped or the land was uplifted, the river would _______ its channel
the ability of streamsto carry a load is determind by: (2 factors)
competence & capacity
measures the largest particles a stream can transport
streams generally erode their channels by lifting loose particles by: (3- a,g, & dsm)
abrasion, grinding, & dissolving soluble material
streams can transport sediment in 3 ways. 1) in solution (_________ ____)
dissolved load
streams can transport sediment in 3 ways. 2) in suspension (__________ ____)
suspension load
streams can transport sediment in 3 ways. 3)scooting or rolling along the bottom (___ ____)
bed load
this 'Load' enters streama through groundwater
dissolved load
this 'Load' is usually expressed by ppm
Dissolved load
ppm stands for
parts per million
the 'Load' in suspension
Suspended load
streams usually carry only ____, ____, & ____ this way
sand, silt, & clay
streams also transport larger particles during a flood b/c H2O ________ increases
part of a stream's 'load' of solid material that is made up of sediment too large to be carried in suspension
bed load
the larger, coarser particles of this load move along the bottom of disneychannel
bed load
occurs as streamflow drops below the critical setting velocity of a certain particle size
the process when a stream seperates solid particles of various sizes, large to small
the sorted material deposited by s tram is called
accumulation of sediment formed where a stream enters a lake or ocean
a landform that parallels some streams; form when a stream overflows its banks
natural levee
a flat valley floor; produced by the side-to-side cutting of a stream
the most prominent features of a narrow valley
rapids & waterfalls
most of the erosion occurs on the outside of the meander--often called the ___ ____--where velocity & turbulence are greatest
cut bank
form in zones of decreased velocity on the insides of meanders
point bars
occurs when the discharge of a stream b/c so great that it exceeds the capacity of its channel and overflows its banks
most floods are caused by (2)
rapid spring snowmealt or storms
new, shorter channel segment is called a cutoff &, b/c of its shape, the abandoned bend is called an
oxbow lake
measures to control flooding include (3: al, fcd, & plofd))
artificial levees, flood control dams, & placing limits on floodplain development
levees that increase the volume of H2O a channel can hold
Artificial levees
store H2O then let it out slowly
flood control dams
allows floodplains to absorb floodwaters w/ little harm to homes & businesses
limiting development
the land area that contributes H2O to a stream
drainage basin
an imaginary line that seperates the drainage basins of one stream from another
much of the H2O in soil seeps downward until it reaches the (zone of)
zone of saturation
the area where water fills all of the open spaces in sediment & rock (zone)
zone of saturation
the H2O within the zone of saturation
the upper level of the saturation zone
the water table
the area above the water table where the soil, sediment, & rock are not saturated
zone of aeration
impermeable layers that get in the way or prevent H2O movement are
the amount of groundwater that can be stored depends on
the % of the total volume of rock or sediment that consists of pore spaces
permeable rock layers or sediments that transmit groundwater freely
aquifers are important b/c they are the source of
forms whenever the water table intersects the ground surface
form when an aquitard blocks downward movement of groundwater & forces it to move laterally
6 degrees C to 9 degrees C warmer than the mean annual air temp. where it occurs
hot spring
an intermittent hot sprong or fountain in which a column of water shoots up with great force at various intervals
occur where extensive underground chambers exist within hot igneous rocks
a hole bored into the zone of saturation
greatest use of well water in the US
irrigation for agriculture
any formation in which groundwater rises on its own under pressure
artesian well
naturally formed underground chamber; when groundwater comes in contact w/ llimestone, the carbonic acid
erosion forms most caverns at or below the water table in the
zone of saturation
calcium carbonate left behind produces the limestone we call
the deposition of dripstone features is not possible until the caverns are above the water table in the
zone of aeration
icicle-like stone pendants that hang from the ceiling of a cavern
form when water seeps through cracks in the cavern ceiling
calcite creates a hollow limestone tube called
soda straw
formations that develop on the floor of a cavernn& reach toward the ceiling
many areas of the world have landscapes that have been shaped laregly by dissolving power of groundwater
karst topography
karst areas typically have irregular terrain, w/ many depressions called
form when bedrock dissolves &caverns collapse
1st thing to remember about narrow & wide valleys
the single most important erosional agent on Earth
running water
if you were to examine the profile of a typical stream, you would probably find that the gradient is
steepest near the head
occasionally, deposition causes the main channel of a stream to divide into several smaller channels called
a cavern is an underground chamber formed by