Ch 8 Geology Exam

Cone of depression

How far the well dips below the water table

Movement of groundwater is exceedingly

Slow from pore to pore

How are slumps and slides related?

Slumps are a type of slide in the special case where the rupture surface is curved.

What happens to rills

They merge to form gullies which eventually join to create streams

why does groundwater discharge to earths surface

earth's surface is irregular, and permeability decreases with depth within Earth

How can pieces of rock in contact with a stream bed move?

rolling, sliding, bouncing

Ultimate base level is

sea level

What is karst topography identified by

sinking streams, solution valleys and depression called sinkholes

What is runoff measured by

stream discharge

Lakes, resistant rocks, and main rivers often act as

temporary or local, base levels that control the erosional and depositional activities of a stream for a period of time

Where does meandering often become very pronounced

Near the mouth of a river where the channel is very near base level

Does subsequent rise in the water table restore porosity and permeability

No the table will not restore porosity and permeability to pre subsidence values

Percentage from oceans =

Ocean evaporation/ total evaporation

how does 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.

Cutback

On the outside of a meander where velocity increases and the stream erodes

Hydrographs

Plots of streamflow, or runoff, over time

Peak flow

Potential flood

Rills

Run off that initially flows in broad sheets form these tiny channels

If the sea level is not dropping, what is a source of water for the oceans in addition to precipitation

Runoff

Does total runoff occur over a longer or shorter time span after an area has been urbanized

Runoff occurs over a shorter time after urbanization

Base level

The lowest point to which a stream can erod

Transpiration

The release of water vapor by vegetation

Lag time

The span between when rainfall occurred and when peak stream discharge occurred

How is the precipitation that falls on the land calculated

The sum total of evaporation, transpiration, runoff and infiltration

What would likely happen to a fence on a hill over time if the fence were built perpendicular to the hill's slope?

The top of the fence would likely bend uphill as creeping rocks moved under the fence and pushed the fence bottom downslope.

stream discharge

The volume of water flowing past a given point per unit of time usually measured in cubic feet per second

What happens when compaction occurs

porosity and permeability are permanently reduced

original source for groundwater

precipitation

What is the water table?

the top of the saturated zone beneath Earth's surface

Worldwide, about how much of the precipitation that falls on the land becomes runoff

35%

Apprx, what percentage of the total water evaporated into the atmosphere comes from the ocean

84.2%

Infiltration

A portion of precipitation that falls on land that soaks into the ground

Widespread lateral erosion by the meandering river produces

A wide floodplain

Whats part of the bed load

Gravel and sand

Serious problem with ground subsidence

As demand for freshwater increases, surface subsidence caused by the withdrawal of groundwater aquifers present a serious problem in many areas

Why do urban areas ofter experience more flash flooding than do rural areas during intense rainfalls

Because of the building covering the surface there is a longer time for the water to be infiltrated so it builds up and causes excess of surface water aka flooding

Hydrolic cycle

Continuous movement of water from the oceans to the atmosphere and then from the atmosphere to the land and then from the land back to sea

How are debris avalanches and flows related?

Debris avalanches are large, rapid flows of rock.

What is the effect of urbanization on lag time

Decreases

What is the general relationship between ground subsidence and the level of water in the well

Directly coorelated

Groundwater moving beneath the surface below the water table flows is which direction?

Downhill perpendicular to the topographic contour lines

What cause meandering paths in down streams from headwaters

Downward erosion becomes less dominant. Instead the rivers energy is directed from side to side

Water table during a drought

Drops

What is the balance between infiltration and runoff influenced by

Factors such as the permeability of the surface material, slope of the land, intensity of the rainfall and type and amount of vegetation.

How is a fall different from creep?

Falls occur rapidly and in areas with high slope, whereas creep occurs slowly in areas with low slope.

Method of measuring the rate of groundwater movement

Involves introducing dye into a well. Time is measured until the coloring agent appears in another well at a known distance from the first

What happens to much of water that falls on land

It doesn't immediately return to the ocean via runoff. Instead it is temporarily stores in reservoirs such as lakes

What happens to most of the water that reaches the land surface

It will infiltrate or run off

What happens when water infiltrates to the depth of the clay lens above a water table

It will store on top of the clay and create an area of saturated zone on top of it

Movement between land surface water and groundwater

Land surface is relatively easy to visualize and the movement of groundwater is less obvious

What is said to resemble karst topography

Landscapes dominated by features that result from groundwater dissolving and removing the underlying soluble rock, usually limestone

In human regions

Mass movements and other slope erosion processes tend to produce V shape valleys

Suspended Load

The fine grained particles that travel in the water column above the stream bed

Downstream from the headwaters

The gradient of a river decreases while its discharge increases because of the additional water that is added by tributaries

How does the use of water by humans affect the water table?

Use of water by humans increases discharge, resulting in lowered water tables.

In arid areas where rivers are eroding what are bedrock valleys

Usually narrow with nearly vertical walls

Where is the head located

Usually well above base level as the source of the rivers or streams

On the inside of a meander

Velocity slows and deposition of a point bar often occurs

Erosion in hydrologic cycle

Wears down the land and shapes earths surface

Water Table

What separates saturated and unsaturated zone

How are rapids and waterfalls formed

When headwater streams run into rocks that are especially resistant to erosion

When does runoff occur on the surface

When the ground becomes saturated, that is when it contains all the water it can hold

Runoff

When the rate of rainfalls exceeds the ability of the surface to absorb it (infiltration)

how much of earths surface water exists in the oceans

almost all of earths surface water exists in the oceans

Which of the following would produce a LOWER water table?

an increase in the amount of discharge to surface water a decrease in the amount of recharge to groundwater

where is most of earths freshwater found

as ice at earths surface

Why is running water the most important that shape earths surface

because rivers and streams are responsible for producing a vast array of erosional and depositional landforms in both humid and arid regions

What are the 3 types of loads carried by streams

bed load, suspended load, dissolved load

Beneath the surface, removal of soluble rock may result in

caves and caverns

Bouncing is to sand as suspension is to

clay

Which of the following are classifications describing how rock and other material move downslope?

fall, slide, slump, creep, flow

Which type of mass movement event requires the addition of water?

flow

When pumping removed groundwater from an aquifer in the Santa Clara Valley

ground subsidence can occur as grains pack more closely together.

Common misconception about groundwater

groundwater occurs in underground rivers that resemble surface streams

Where do running water features begin

headwaters of a river while others are found near the mouth

what does the hydrologic cycle describle

how liquid and gaseous water moves between the ocean, atmosphere and land

Where does groundwater exist

in the pore spaces and fractures in rock and sediment

Does urbanization increase or decrease the peak streamflow

increASE

Sliding is to gravel as dissolution is to

ions

What do factors such as climate, steepness of slope, surrounding material, vegetation and degree of urbanization produce

local variation in the globally uniform exchange of water balance

where do meanders originally occur

midway through their course

what is mass movement

movement of material under the influence of gravity alone

Globally, from which source does more water evaporate into the atmosphere, ocean or land?

ocean

what would happen to atmospheric water if earth were mostly covered with land

the atmosphere would contain less water

What would happen to the oceans if surface runoff and groundwater flow did NOT occur?

the oceans would become smaller

which ocean is earths largest

the pacific ocean

what is the cone of depression

the shape that the water table takes on near a pumping well

Initial power source for the water cycle

the sun

how does the water table change around a pumping water well

the water table elevation decreases

How would the water table be affected if Earth were made up of uniform, permeable material?

the water table would not exist

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 go dry

when the cone of depression of a second well intersects the deepest part of the well

Lateral erosion by a meandering river

widens the valley floor and a floodplain begins to form