Final Flashcards
Soil make-up
- 25% air
- 25% water
- 45% mineral matter
- 5% organic matter
The hydrosphere make-up
- 97.2% ocean
- 2.15% glaciers
- .62% groundwater
The hydrologic cycle
evaporation, precipitation, run off, infiltration
What is a river/ stream?
Water flowing at Earth’s surface in a confined channel
What is a river/stream’s gradient?
The slope of the stream
what is a river/stream competence?
The largest grains the river can carry
With increasing gradient, the _________ increases
competence
What river has a high competence?
Colorado river
Fossils with a narrow age range and a wide distribution commonly used to determine the relative and/or absolute age of a rock unit are called:
Index fossils
The radioactive decay of a parent isotope gives rise to:
Daughter elements
In analyzing a sample of charcoal that contains 25% of the original Carbon-14 that has a half life of 5730 years, how old is the sample
~11,460 years old
Steno’s laws
rules for determining the order in which rocks were deposited in
Principle of superposition
The bottom layer is older than the layers on top
Principle of original horizontally
Particles and sediment is deposited horizontally
Principle of lateral continuity
Sediment deposition is laterally continuous until there is a change in in environment
Principle of cross cutting relationships
fractures in rock are younger than the rocks
Unconformity:
represents a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed.
Angular Conformity:
Consists of tilted or folded sedimentary rock that are overlain by younger, more flat-lying strata.
Fossils are used to correlate between _______
rock units
Conditions that favor preservation (fossils)
- rapid burial
- organisms with hard parts (skeletons, shells, etc.)
What do fossils tell us?
- Age of a rock
- Community dynamics
- Type of environment (wet/dry, marine/non-marine)
Absolute age dating
- primarily in igneous rock
- half life
- isotopes
- radioactive dating
Isotopes:
An atom of an element with different # of neutrons
Half-life:
Time needed fir 1/2 of parent to decay
Sources of error of radioactive dating
- No daughter atoms
- fresh, unweathered samples should be used
- wrong isotopes
The geologic time scale:
-formed using both absolute and relative dating
-separated mostly by observed evolutionary change
-(in order from greatest to least)
Eons, eras, periods, epochs, stages
Metamorphic rocks:
Rocks that have been changed texturally, mineralogically, and/or chemically
Temperatures in the crust rise with depth. This feature of the earth is called:
Geothermal gradient
Metamorphism occurring over large areas is known as:
Regional metamorphism
The proper order of Slate by increasing metamorphic grade:
Slate, phyllite, Schist, Gneiss
_____ in metamorphic rocks occurs due to differential stress
Foliation
Waterfalls migrate upstream through the process of:
Knickpoint migration
A geologic unit composed of highly porous, gravel-rich materials would likely make a good _____
aquifer
What are the key factors influencing the erosion and deposition of a stream:
- Velocity
- Channel dimensions
- Discharge
What are the three movements of sediments within the bedload of a stream/river?
- rolling
- sliding
- saltation (bouncing)
Aquitard:
A layer of geologic materials which impedes groundwater movement
Artesian wells generally result from:
well installations in a confined aquifer
Groundwater which is NOT overlain by an impermeable layer of geologic materials is said to be:
Unconfined
Metamorphic environments:
- Deep basins
- fault zones
- Impact zones
Foliation:
preferred mineral grain orientation due to differential stress
What sediments align in minerals due to direction of stress
-Micas, amphiboles, pyroxenes
Why do some rocks foliate and others do not?
The parent rock’s minerals are either are or are not micas, pyroxene, amphiboles
Capacity:
maximum solid load of a stream can carry
What is the mission of a river?
To get water and sediments to base level
What is base level?
An ocean, lake, or another basin
What keeps rivers and streams from forming a water world?
Plate tectonics
What is a water fall?
A local base level, the resistant rock ledge(which limits the waters ability to erode deeper.
Knickpoint migration:
movement of a waterfall
How do streams flow?
- streamflow
- velocity
streamflow:
controlled by velocity
Velocity:
speed of the river
Laminar flow:
smoother flow (streams)
Turbulent flow:
chaotic flow (rapids)
What are drainage basins?
Area where all water that falls in the area, will drain into that basin (stream order)
Stream order:
Measurement of the relative size of streams
Two types of streams:
- Braided
- Meandering
- Type depends on proximity to head waters, farthest from where stream meets discharge outlet
Braided stream:
- High energy
- typical mountain drainage
- over time turns to meandering stream
Meandering stream:
- lower energy
- associated with flood plains
Factors affecting erosion and deposition of a stream:
- velocity gradients
- shape, size, and roughness of channel
- discharge
- gradient: the different river flows within a channel
What point in a stream has the maximum velocity?
The center
How do streams transport sediment?
- rolling
- sliding
- saltation (bouncing)
Sediments contacting at the bottom of the river is the:
bed load
Sediments that are are floating in the water is the:
Suspended load
Point bar:
The inner curve of a bend, deposits sediment
Cut bank:
The outer curve of a bend, erosional
Where do streams slow down?
- Channel deposits
- ex. Point bars and deltas
Deltas:
-Where rivers meet base level they are forced to slow and drop the sediment
Direction that rivers migrate:
left and right (meandering)
up and down (downcutting)
stream capture:
- drainages running into each other
- two 1’s meeting makes a 2, two 2’s meeting makes a 3…etc
How to calculate discharge:
- measurement of how much the river is outputting
- cubic feet per second
- Discharge= (velocity)(depth)(width)
Increased disharge=
Increased capacity
Increased velocity=
Increased competence
Types of deltas:
- River dominated delta (bird foot delta)
- Wave dominated delta(Triangular or “delta” shaped)
- Tide dominated delta
River dominated delta (bird foot delta):
- Sediment makes its way to ocean
- ex. Mississippi river
Wave dominated delta (triangular shaped delta):
- Sediment is deposited at mouth of river
- Ex. Nile river delta
Tide dominated
- Island bars running parallel to river output
- ex. Fly river delta, New Zealand
Types of floods:
- Regional
- Flash
Regional flood:
large area flooding
Flash flood:
- localized flooding usually due to storms
- Ice jams and dam failures can cause heavy precipitation
Flood recurrence interval
ex. “100 year flood”
- within a 1/100 chance of that size of flood happening in a year
Flood control methods:
- dams
- levees (sides of a river built higher)
- channelization (LA river, straightened and steepened)
- Management (passing no building laws)
Rural flooding:
- less severe
- longer “lag” time
- lots of grass and soil to soak up some flow
Urban flooding:
- more severe
- less “lag” time
Slot canyons:
-narrow canyon carved by massive flooding events
Zone of aeration:
area of subsurface that is not fully saturated (moist soil)
Pore space:
space between sediments that can be filled with water
Capillary fringe:
beginning of zone of saturation
Zone of saturation:
100% saturated
Porosity:
-percentage of volume of rock or sediment that consists of pore spaces
Specific yield:
the measurement of how much free flowing water can come out of it
Specific retention:
the water that will not be free flowing
Permeability:
the ability of water to move between the grain gaps, the ability to transmit a fluid
Clay permeability example:
Porosity: 50
Specific yield: 2
Specific retention: 48
How to calculate hydraulic gradient:
H1-H2/distance
Water will always move _____ to contour line
perpendicular
Aquitard:
An impermeable layer that has low specific yield and does not transfer much water
Aquifer:
rock strata or sediment that transmits groundwater freely
Aquifer types:
- perched
- confined
- unconfined
Confined aquifer:
aquifer that is confined between two aquitards
Unconfined aquifer:
aquifer that is not overlain by an aquitard
Perched aquifer:
Is above an aquitard, ca be above surface water level
Groundwater is often:
- Mildly acidic
- Contains weak carbonic acid
How is groundwater formed?
-When rainwater dissolves Carbon Dioxide from the air and from decaying plants
How can groundwater form lakes?
Karst topography: the groundwater dissolves limestone and leads to it collapsing
What are hot springs evidence of?
groundwater movement
What are some problems associated with groundwater?
- It is a non-renewable source
- the occurrence of subsidence (deflation of land)
- saltwater contamination
How is groundwater movement dictated?
by gravity and geological conditions
Two types of glaciers:
- Alpine: exist in mountains
- Continental: ice sheets (antarctica and greenland)
Zone of accumulation:
base line of the glacier (top)
Zone of wastage:
Where the glacier begins to reduce itself
The glacial budget:
more or less material will reflect on the zones of accumulation and wastage
How do glaciers move?
(Zone of fracture)
———————————-
-Internal flow (Inside)
Crevasses
linear cracks in glaciers due to movement of glacier
Plastic flow of glacier
Center of glacier moves
How do glaciers erode?
By grinding rocks and transporting sediments
Striations:
- Hints at directions of glacier movement
- Scratched by moving sediments
Polished surfaces:
Result from sand paper-like glacial ice grinding down rock
Cirques:
A bigger zone of accumulation
Arete:
Spine like tops between glaciers
Horn:
Several cirques coming together, making a pyramid-like horn
Truncated spurs:
formed by the main glacier eroding many arete’s in the system
V-shaped valleys mean:
They were carved by a stream and are unglaciated
U-shape valleys mean:
They were carved by glaciers
Tarns:
Lake located in an iceless cirque
Fjords:
Flooded glacial valley
Hanging valleys:
- waterfalls with huge drop-offs
- where supporting glaciers meet the valley of the main glacier
Glacial till:
- Unstratified and unsorted
- From glacial deposits
- sediments drop where ice melts
Medial Moraine
- Ex. Mt mckinley
- build up of glacial till
- Usually in ablation
Terminal moraine
- The furthest the glacier reached
- during melting, the glacier deposits till making a hill
Recessional moraine
- Interior of glacier
- from grow and retreat
- younger than terminal
Ice can deposit ice in a _______
kettle lake
Esker and games form by:
movement under the ice
Drumlins:
Steep face will face the glacier
lateral moraines:
-Form on sides/margins of glaciers
Kettle lakes:
debris and ice depress the earth and melts, leaving a lake
Isostatic subsidence:
- Glacial ice can depress the earth’s surface
- rebound: after ice melts, the earth takes a while to go back to normal
The laurentide Ice sheet:
- North America
- 95-20 thousand years ago
- deglaciation produced the great lakes and long island
The three natural phenomenon that controls glaciation are:
- Earth’s orbit around the sun that changes
- Earth’s tilt also not constant from 23 1/2
- Earth’s precession
Ice Cores:
-preserve atmospheres of atmospheres (air bubbles, air chemistry, CO2 levels)
Right now, we are in a
glacial period
Deserts are:
- Hot
- Dry
- Cold
- < 25 cm of precipitation/ year
Most deserts occur at ______ latitude
30 degrees
tropic of cancer and tropic and capricorn
_____ ___results in dry and arid areas
falling air
Types of deserts:
- Polar
- Rainshadow
- Inland
- Western Coastal
Polar deserts:
-occur at the poles
Rain shadow deserts:
- Associated with topographic features, usually mountains
- ex. Death valley
Inland deserts:
fair removed from any water source
Western Coastal deserts:
Associated with ocean currents and cool water upwelling
Playas:
dry lake beds
Bajada:
set of alluvial fans
Inselberg:
mountain island , a single mountain
Elevated flat areas in the desert:
Plateus - mesas - buttes
————————————->
largest to smallest
What is the key to erosion and transportation in the desert?
air
blowouts:
sand removed from an area by wind
deflation:
small particles removed leaving a hard crust called Desert pavement
The three factors that determine the type of sand dunes
- Wind direction and strength
- Sand supply
- Vegetation that is present
