Chapter 22
Sand dunes can form
In an area where wind-blown sand grains are blocked by an obstacle
What is part of a bed load
Gravel and sand
sandy soils tend to have
High porosity and high permeability
What are cross beds?
Inclined layers in sediment or sedimentary rocks that reveal the direction of wave or wind transport
How does the water get from the oceans onto land?
Ocean water evaporates to form gaseous water and moves into the atmosphere, where it condenses into liquid water and falls out of the atmosphere to land as rain.
How are oxbow lakes formed?
Oxbow lakes form when one meander erodes into another, cutting off water to part of the stream channel.
The amount of water the ground can hold and the ability of the ground material to allow water movement are called
Porosity and hydraulic conductivity
Although glaciers are a frozen ice mass, they flow due to
Pressure and plastic flow, and basal sliding
Water that does not infiltrate into the ground or evaporate becomes
Runoff
Karst topography is characterized by
Sinkholes caves and caverns
Scientists can determine the direction of ancient ice movement by looking for
Striations, roches moutonnaces, and drumlins
What would happen to atmospheric water if Earth were mostly covered with land?
The atmosphere would contain less water.
What does the hydrologic cycle describe
The hydrologic cycle describes how liquid and gaseous water move between the ocean, atmosphere, and land.
What do cross beds represent?
The moving front of a ripple or dune
What would happen to the oceans if surface runoff and groundwater flow did not occur?
The oceans would become smaller.
How does the water table change around a pumping water well?
The water table elevation decreases.
Where do valleys tend to form in a landscape?
Valleys form where rock layers are easily erodible (soft).
Below the ground, water moves from
Where the water table is high to where the water table is low
As a stream moves downslope, the gradient gradually decreases and the channel
Widens and discharge increases
Why do dunes migrate?
Wind eroded material on the back side of the dune and deposits it on the front side of the dune
The water table is found at the top of the
Zone of saturation
What is a floodplain?
a flat surface next to a river channel
What is a meander scar
a landscape feature formed after an oxbow lake dries up
What is an oxbow lake?
a meander that has been cut off from the original stream channel
What is a natural levee?
a ridge of flood deposits next to a river channel
What are three types of loads carried by streams?
bed load, suspended load, dissolved load
Bouncing is to sand as suspension is to
clay
What is the dominant fluvial process in a clear, sediment-poor stream moving down a steep slope
downcutting
The greater the hydraulic gradient the
faster flow
Sliding is to gravel as dissolution is to
ions
A rock that is readily attacked by chemical weathering is
limestone
Land subsidence is caused by
over-pumping of groundwater and the compaction of clay layers.
How can pieces of rock in contact with a stream bed move?
rolling, sliding, bouncing
How do pieces of rock move under the influence of wind?
rolling, sliding, bouncing, suspension
What property of a piece of material will most directly determine how it is carried by the wind?
size
What is suspended load?
the fine-grained particles that travel in the water column above the stream bed
What is dust?
the particles carried in suspension by wind
What is a cone of depression?
the shape that the water table takes on near a pumping well
Which processes result in the widening of the floodplain of a meandering stream
undercutting and lateral erosion
When will a cone of depression stop enlarging?
when the amount of water flowing toward the well equals the amount of water being pumped out of the well
When might a well, Well A, go dry?
when the cone of depression of a second well intersects the deepest part of Well A
The order of distribution of earths freshwater (a) ground water (b) polar ice caps and glaciers (c) streams, rivers, and lakes (d) soil moisture
(B) polar ice caps and glaciers (A) groundwater (C) streams, rivers, and lakes (D) soil moisture
A streams erosive power is greatest
Where discharge and velocity are greatest
From most to least rank these in their susceptibility to chemical erosion: (a) marble (b) limestone (c) sandstone (d) quartzite
(B) limestone (A) marble (C) sandstone (D) quartzite
rank the stages of glacial flow: (a) basal sliding (b) crevasses (c) accumulation and thickening of glacial ice (d) calving
(C) (A) (B) (D)
How much of Earths surface water exists in the oceans?
Almost all of Earth's surface water exists in the oceans.
Where is most of Earth's freshwater found?
As ice at Earth's surface
What is the relationship between water currents and cross beds?
Cross beds sit at an angle to current direction.
Where do deposition and erosion of material occur along a meander?
Deposition occurs on the inside of the meander, whereas erosion occurs on the outside.
The dominant processes in the hydronic cycle are
Evaporation and precipitation
Which type of stream is associated with the formation of an oxbow lake?
Meandering stream
The overpumping of groundwater can result in
Land subsidence and sinkholes
How does the formation of a natural levee impact flooding?
Natural levees raise the height of the stream channel, reducing the amount of flooding that will occur on the floodplain.