Which of the following paleoclimatic evidence supports the idea of the late Paleozoic super continent in the Southern Hemisphere?
rocks formed by glaciers in South Africa and South America
The ________ is an example of an active, continent-continent collision.
northward movement of India into Eurasia
Deep-focus earthquakes, those between 300 and 700 kilometers below the surface, occur only in association with ________.
Linear, magnetic patterns associated with mid-ocean ridges are configured as ________.
normal and reversed magnetized strips roughly parallel to the ridge
Which of the following energy sources is thought to drive the lateral motions of Earth's lithospheric plates?
export of heat from deep in the mantle to the top of the asthenosphere
The continental drift hypothesis was rejected primarily because Alfred Wegener could not ________.
identify a mechanism capable of moving continents
All of the following are evidence supporting the theory of plate tectonics except for ________.
changes in the Moon's orbit due to shifting plates
Which one of the following most accurately describes the volcanoes of the Hawaiian Islands?
shield volcanoes fed by a long-lived hot spot below the Pacific lithospheric plate
oceanic crust and lithosphere are formed at ________.
divergent boundaries by submarine eruptions and intrusions of basaltic magma
Cooler, older, oceanic lithosphere sink into the mantle at ________.
subduction zones along convergent plate boundaries
Deep ocean trenches are surficial evidence for ________.
sinking of oceanic lithosphere into the mantle at a subduction zone
A transform plate boundary is characterized by ________.
a deep, vertical fault along which two plates slide past one another in opposite directions
The modern-day Red Sea is explained by plate tectonics theory because it is ________.
a rift zone that may eventually open into a major ocean if Arabia and Africa continue to separate
The volcanoes and deep valleys of east Africa are related to a ________.
continental rift along which parts of the African continent are beginning to slowly separate
________ most effectively outline the edges of the lithospheric plates.
Lines of earthquake epicenters
The elastic rebound theory for the origin of earthquakes was first proposed by ________ following the ________ earthquake.
Reid; 1906, San Francisco
Which one of the following statements concerning foci and epicenters is correct?
The epicenter is at the surface directly above the focus where the earthquake initiates.
Which one of the following is true regarding tsunamis?
They occur in the open ocean, wavelengths are many miles or kilometers and wave heights are only a few feet.
The ________ magnitude scale is a measure of the energy released. It does not directly measure the extent of building damage.
Why was the Marina District, San Francisco, heavily damaged in the 1906 and 1989 quakes?
Liquefaction and foundation failures were common.
The ________ is directly related to the Richter earthquake-magnitude rating.
amplitude of the seismic waves
Approximately how often do locked segments of the San Andreas Fault (California) break, resulting in major earthquakes?
once every hundred and fifty years
________ refers to the tendency for a foundation material to lose its internal cohesion and fail mechanically during earthquake shaking.
Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5?
________ is a widely accepted explanation for the mechanism that generates earthquakes.
Reid's elastic rebound theory
The Mercalli Scale is a scale from ________.
I to XII that rates the structural damage due to an earthquake
The largest lateral, ground displacement is produced by ________.
horizontally vibrating surface waves
The ________ is used to record ground shaking and the earthquake-magnitude scale was invented by ________.
The epicenter of an earthquake is the ________.
surface location directly above the point where the fault slip initiates
________ was struck by three major earthquakes during the winter and spring months of the years 1811-1812.
Deposition of dissolved minerals in caverns leaves deposits such as the icicle like _____.
Caves are found in most parts of the world where there are thick _____ deposits under the surface.
The production of travertine first requires that ______ dissolves in hot water and makes an acid that dissolves great quantities of limestone.
The rapid appearance of sinkholes in Florida can be explained by .....
buildings built on top of bedrock cavities.
Which three substances are required to interact to form calcium bicarbonate?
Water, carbone dioxide, and lime
In hydrothermal situations, superheating of water is possible because of the presence of _______.
What is the circulation within Earth's outer core responsible for?
The generation of Earth's magnetic field
What is isostasy?
It refers to the crust's ability to sink down into the mantle when the crust's mass increases and to rebound when its mass is lessened.
Felsic igneous rocks contain large portions of ______ while mafic igneous rocks contain large portions of ________.
Light colored silicate minerals; dark-colored silicate minerals.
The doctrine of ______ holds that the processes that are shaping the contemporary landscape are the same processes that formed topography of the past and are the same processes that will shape topography of the future.
The totality of minerals ejected from a volcano including liquid material, ashes and dust is termed:
Earth has a heavy, solid inner core surrounded by three concentric shells-outer core, mantle, and crust- of various densities and compositions.
Geomorphologists focus on understanding the internal and external processes that affect the formation of landforms.
Which of the following is the specific name given to the study of the characteristics of rocks?
The process of ______, involves the lowering of continental surfaces and is accomplished by a combination of three processes: weathering, mass wasting, and erosion.
Water is major agent of weathering because of its property that, when it freezes, it decreases in density and.....
The process of hydrolysis involves ________.
the chemical union of water with another substance to yield to a compound that is weaker than the original rock or mineral.
A slope collapse with a backward rotation, often characterized by a crescent-shaped scarp face is a _____.
_________ involves the peeling of thin layers of stone off a large rock and might happen directly as a result of the removal of an overlying weight from the landscape.
A soil pH measuring 7 on the standard pH scale is considered:
neutral hence most suitable for majority of plants and microorganisms.
Weathering loosens surface and near-surface material in bedrock and makes it prone to mass wasting and erosion.
Mechanical weathering processes include frost wedging, salt wedging, and temperature changes in rock.
Biological weathering is relatively minor; it involves the effects that burrowing animals, plant root penetration, and organic acids have on the other two weathering processes.
The three general weathering processes are interrelated and are influenced to varying degrees by the climate.
There are a several mass wasting processes, but they all transfer weathered materials down slopes under the influence of gravity.
A weathering type associated with curved and concentric sets of joints break away in successive layers is called ______.
The general term signifying the overall lowering of the rock material on the Earth's crust is ________.
The rock debris which accumulates at the base of steep slopes by gravitational actions is called _________.
Water is a major agent of weathering because of its property that, when it freezes, it decreases in density and _______.
expands in volume.
The single most important mechanism of transport for weathered overburden in the subarctic zones is _______.
________ might happen directly as the result of the removal of an overlying weight from the landscape.
The location of features, such as cliffs and valleys might be strongly influenced by the position of ______.
Large _____ extend for considerable distances and depths through rock. Below the surface, there is minimal separation between the blocks on either side.
The slight displacement of human built structures such as fences, posts, and telephone poles is subtle evidence that _____ has occurred.
Which of the following form of mass wasting is relatively fast and wet compared to the others?
The steepest angle that can be assumed by loose fragments on a slope without downslope movement is the angle of repose.
Which one of the following applies to a valley glacier that lengthens (extends its terminus downslope) over a period of many years?
Accumulation exceeds wastage.
A ________ cross-valley profile is typical of canyons and valleys eroded and deepened by alpine or valley glaciers.
Which of the following glacial features would typically be found in close proximity?
hanging valley and truncated spur
What type of moraine would be most useful for tracing diamond-bearing kimberlite fragments directly to their bedrock source area?
lateral, valley or alpine glacier
________ is the best explanation for a glacial surge.
Melting at the base of the glacier resulting in increased rates of basal slip
The ________ of the geologic time scale represents the time of the most recent "Ice Age."
How do icebergs in the North Atlantic Ocean originate?
by calving of large piedmont glaciers in Greenland
What type of moraine is formed by the merging of two lateral moraines at a junction of two valley glaciers?
Which of the following is often associated with a cirque basin in high, mountainous terrain?
________ have rainfall amounts and soil moisture contents between those of true deserts and humid lands.
A ________ is an intermittent stream channel in the dry land areas of the western United States.
Which one of the following will effectively limit further deflation in a given area?
Which one of the following statements is correct?
Alluvial fans typically rim desert valleys; playas form in the lowest, interior parts of the valleys.
Which of the following characteristics would suggest geologically recent, fault uplift of a desert mountain range?
flat, upland surfaces, steep slopes and small alluvial fans
How is desert pavement formed?
Runoff and deflation carry off the silt and clay, leaving coarser particles behind.
Which one of the following is the one best measure of the wetness or dryness of a region?
difference between annual precipitation and evaporation potential
How are sand grains transported by the wind?
by saltation in the first few meters above the land surface
Which of the following best describes the climatic factors that cause low latitude deserts like the Sahara in Africa?
Cool, dry air aloft is descending; surface winds are blowing toward the equator.
Loess deposits in the central United States ________.
originated as rock flour in Pleistocene glacial streams and rivers
Assume that the central slip face of a barchan dune slopes downhill toward the east. What is the direction of the prevailing wind?
west to east
During a typical sandstorm, saltating sand grains reach a maximum height of ________ above the land surface.
why is it said that groundwater is the largest store of freshwater on earth that is "readily available to people"?
when ice is excluded and just liquid water is considered, more than 94% of all freshwater is groundwater
what is the water table?
water table is the upper limit of the zone of saturation and is a very significant feature of the groundwater system; it is important in predicting the productivity of wells, explaining the changes in the flow of springs and streams, and accounting for fluctuations in the levels of lakes
how can you find out where a water table is?
its elevation can be mapped and studied in detail where wells are numerous bc the water level in wells coincides w the water table
zone of saturation (phreatic zone)
where water that is not held as soil moisture percolates downward until it reaches a zone where all of the open spaces in sediment and rock are completely filled with water
unsaturated zone (vadose)
the area above the water table that includes the capillary fringe and zone of soil moisture
what holds water around sedimentary particles?
the capillary fringe that extends upward from the water table and groundwater is held by surface tension in tiny passages between grains of soil or sediment; (capillus= hair)
in a given volume of sediment, what texture would hold more water in an unsaturated state, clay or sand? why?
clay because it has a high porosity because it is packed tightly and sorted well
water soaks into the ground bc bedrock, sediment and soil contain countless voids or opening that are similar to a sponge
which sediment would you expect to have the greatest porosity?: limestone, poorly sorted alluvim or clay?
which sediment would you expect to have the greatest permeability: clay or sand?
clay's ability to store water is great (high porosity) but its pore spaces are sos mall that the water is unable to move through it so it has poor permeability (aquitard); but larger particles like sand or gravel have larger pore spaces so water moves with ease (aquifiers)
why is it important to know the hydraulic gradient for groundwater in an area where one might want to build a home and tap into an aquifier to supply drinking water?
velocity of groundwater flow is proportional to the slope of the water table- the steeper the slope, the faster the water moves (bc the steeper the slope, the greater the pressure difference b/t 2 points): made by Henri Darcy (Darcy's Law)
the flow velocity varies with the permeability of the sediment- groundwater flows more rapidly through sediments having greater permeability; this is the coefficient that takes into account the permeability of the aquifier and viscosity of the fluid
what are the factors that determine the hydraulic gradient?
measuring difference in elevation between two points on the water table (h1-h2) divided by the distance between them (d); wells are used to determine the heigh of the water
what determines groundwater movement and how fast?
measured directly using various dyes and carbon-14
where do you get springs? for example, why dont we have a spring popping up in front of dallas halls?
the source of springs is water from the zone of saturation and the ultimate source of this water is precipitaion; whenever the water table intersects Earth's surface, a natural outflow of groundwater results (spring);
where are we likely to find hot springs?
temperatures in deep mines and oil wells usually rise with increasing depth; so when groundwater circulates at great depths is becomes heated and if it rises to the surface, the water may emerge as a hot spring; 95% of hot springs in US are found in the West bc the source of heat for most hot springs is cooling igneous rocks
where do springs form?
when an aquitard blocks the downward movement of groundwater and forces it to move laterally; a spring results where the permeable bed outcrops
by definition, the water in hot springs is 6-9 degrees Celsius; warmer than the mean annual air temperature for the localities where they occur
intermittent hot springs or fountains in which columns of water are ejected with great force at various intervals
perched water table
a type of spring formation where an aquitard is situated above the main water table, as water percolated downward a portion of it is intercepted by the aquitard, creating a localized zone of saturation and a perched water table
the most common method for removing groundwater; a hold bored into the zone of saturation; serve as small reservoirs into which groundwater migrates and from which it can be pumped to the surface; MUST penetrate below the water table
the effect whenever water is withdrawn from a well, the water table is lowered; decreases with increasing distance from the well
cone of depression
result from a drawdown and forms a depression in the water table, roughly conical shape
what is an artesian well?
any situation in which groundwater under pressure rises above the level of the aquifier
what conditions have to be met to have an artesian well?
(1) water is confined to an aquifer that is inclined so that one end can receive water and (2) aquitards, both above and below the aquifier, must be present to prevent the water from escaping which is called a confined aquifier
flowing artesian well
when the pressure surface is above the ground and a well is drilled into the aquifier
non reable resource
in some regions, groundwater has been and continues to be treated as this which means the water available to recharge the aquifier falls significantly short of the amount being withdrawn
a non reable resource spot; has low rainfall, high evaporation which means little recharge: decline in texas with over 150 ft. since agricultural development
what are 3 problems that arise from heavy pumping of well water in a region with a slow recharge rate (not enough rainfall to replenish the groundwater)?
(1) treating groundwater as a nonreable resource; (2) subsidence; (3) saltwater contamination
when the ground sinks and water is pumped faster than natural recharge processes ex: San Joaquin Valley of California
because fresh water is less dense
than saltwater, it floats on the saltwater and forms a large
lens-shaped body; the depth of the fresh water below sea level is about
40x greater than the elevation of the water above sea level
*so when excessive pumping lowers the water table by a certain amount, the bottom of the freshwater zone will rise by 40x that amount ; therefore if groundwater withdrawal continues to exceed recharge, there will come a time when the elevation of the saltwater will be sufficiently high to be drawn into wells, thus contamination the freshwater supply
how does groundwater contamination happen, especially where there is heavy pumping of well water for drinking?
one common source of groundwater
is sewage; if sewage water that is contaminated with bacteria enters the
system, it may become purified by natural processes; permeable layers
transmit quickly (not purified) and slower movement allows water to be
purified (sand, permeable sandstone)
other sources of contamination: highway salt, fertilizers, pesticides, chemical/industrial materials
what are subsurface and surface structures associated with karst topography?
-sinkholes or sinks- irregular terrain punctuated with many depressions
-lack of surface drainage (streams)- following rainfall, the runoff is quickly funneled below ground through sinks and flows through caverns until it reaches the water table but this is where streams do not exist at the surface and their paths are usually short
-carbonate, sulfate, or salt beds at/near ground surface
-characterized by solution valleys, disappearing streams and sinkholes
a speleothem; icicle like pendants that hang form teh ceiling of the cavern and form where water seeps through cracks above
speleothems that form on the floor of a cavern and reach upward toward the ceiling water galls from the ceiling and splatters over the surface
what are cave pillars made of?
depositional features created by the seemingly endless dripping of water over great spans of time; the calcium carbonate that is left behind produces the limestone we call travertine
Important Geological Agent
-Eroding, transports, deposits sediments
-moves mess from continents to ocean basins
Sources of Earth's Water
Oceans - 97.2 %
Other- 2.8 %
-Glaciers - 2.15%
-Ground Water- .62%
-Freshwater Lakes- .009%
-Saline Lake/Inland Seas- .008%
-Stream Channels- .0001%
Stream flow begins as water is added to the surface
-Melted snow adds water
-snow and rain add water
-swamps and puddles collect water on flat land
Stream flow begins as a moving sheetwash
-thin surface layer of water
-moves down steep slopes
-erodes the substrate
Intense scoring marks entry into the channels
-rapid erosion lengthening the channel further upslope
Land areas that drain into a specific trunk stream
-Also known as CATCHMENTS or WATERSHEDS
Watersheds exist in a variety of scales
-Feed large rivers
Continental divides separate flow to different oceans
-Flows all year
-At or below the water table
-Humid or temperate
-Discharge varies seasonally
-Not flow all year
-Above the water table
-flow mostly during rare flash floods
Amount of water flowing in a channel
-volume passing a point per unit of time
-cubic feet per second
-cubic meters per second
-Given by a cross-sectional area times flowing velocity
-varies seasonally due to precipitation and runoff
Example: Niagara Falls (200,000 ft3/sec)
Discharge = Q x A
Not uniform in all areas of channels
Friction shows water along the edges creates greater friction
Maximum velocity travels the outside curve
-outside curve is preferentially scoured and deepened
-Deepest part of the channels is the THALWEG
-flow around curve follows a spiral path
Stream flow is characteristically turbulent
-chaotic and erratic
Stream flow doeswork
-energy imparted to streamflow is derived from gravity
-streams do work by converting potential to kinetic energy
Maximized during floods
-Large water volume
-high water velocities
Streams SCOUR, BREAK, ABRADE, and DISSOLVE
Breaking and Lifting
Force of water can...
-break chunks of rock off the channel
-lift rocks off the channel bottom
-Sediment grains in flow "sandblast" rocks
-bedrocks exposed in channels often polished and smooth
-Gravel surrounding turbulent eddies drills holes in the bedrock
-bowl shaped depresions - POTHOLES
-Unusual and intricate sculptes
When velocity of flow decreases
-Competence is reduced and sediment drops out
-Sediment grain sizes sorted by water
-sands removed from gravel, mud from both
-Gravel settles in channels
-Sands drop out near channel environments
-silts and clays drape flood plains away from
Streams Guide Sediment with Transport
Biggest particles typify steep gradients in head waters
Fine particles typify gentler gradients near mouth
Fluvial sediments are called this
-Channels are decorated with mud-channel bars
-sands build up to t he point bars inside meander beds
-muds deposit from channel during floods
-streams builds a sediment delta upon entering fan
-Changes character with distance
-In profile, gradient describes a concave-up curve
Near the HEAD WATER source of the stream
Gradient is steep
discharge is low
channels are straight and rocky
Toward the Mouth...
Smaller grains typical
Channels describe broad meander belts
Lowest point a stream can erode
-ultimate base is sea level
-can't erode below
-A lake serves as a local (or temporary) base level
Base level changes cause stream...
-Raising base level results in an increase in deposition
-Lowering base level accelerates erosion
-A ledge of resistant rock may define local base level
-Erosive forces act to slowly remove the resistant layers
-Act to restore longitudinal profile
Valleys and Cannons
Stratsgraphic variations often yield a stair step profile
-Strong rocks yield vertical cliffs
-Weak rock produce sloped walls
-Geologic processes stack strong and wear rocks
-Valleys stowe sediment when base level is reached
-Reed incision creates stream terraces
-terraces mark former flood plains
Are turbulent water with rough surface
-Reflect geologic control
-Flow over bed rock steps
-Over large clasts
-prompt narrowing of a channel
-sudden increase in gradient
Streams cascade or free fall
Energy causes a PLUNGE POOL at base
Erosion initiates collapse of overlying rocks
-temporary base levels
Lake Erie drops 55 m flowing toward Lake Ontario
-Dolostone rock is resistant, underlying shale erodes
-Blocks unsupported dolostone collapse and fall
-Falls continuously erode south to lake erie
-Erosion shows deglaciation has formed Niagara Gorge
-Diversion of falls reveals huge blocks of rock
-Rate of waterfall retreat- present .5 m/yr
-Erie will drain when falls reach it
Sediments rapidly dropped near stream source
-coarsest material found near stream source
-sediments fine and thing away from source
Sediments create conical, fan shaped stretches
Forms at base of a mountain front
Channels choked by sediments
Flow formed around sediment obstructions
-DIVERGING- converging flow creates sand and gravel BARS
-Bars unstable, sand and gravel cannot stick together so it eventually collapses (no cut in the channel from stream)
Channels can form intricately looping curves
-travel over broad flat-plains with underlying soft substrate
-Region where river has a gentle gradient
-Meanders increase volume of river by making longer
-Become sinuous with time
Water on the outside of the channel flows fastest and erosion eats away at the channel walls creating a cut bank.
Inside edge of channel has slow moving water such that the competence decreaes and sediment accumulates creating a wedge also known as POINT BAR
Meandering stream channels cover a small portion
Typically has escarpment or bluff along sides and channels over flow to flood plains in entire region
When stream enters standing water
-current slows and loses competence, dropping out sediment
-Forms a number of distributaries
Landscapes evolve over time
Stream flow causes most changes
EX: -Uplift sets base level
-Stream cuts former surface
-Valleys widen, hills erode
-Landscape divided to base level
When streams cut down into landscape that was originally near the stream's base level
-A situation in which headward erosion causes one stream to intersect the coarse of another stream
Tectonic Uplift can alter a course of a major river
Early Mesozoic, South American drained westward
Western uplift raised Andes
- now flows east
Streams carve channels into the
flat strata; when they eventually erode down through the unconformity
and start to downcut into the folded strate, they maintain their earlier
course, ignoring the structure of the folded strata
-pre-existing geometry has been laid down on the rock structure
As a mountain uplifts, the stream downcuts just as fast maintaining its original course, cutting across the range.
Devestate people and property
During a flood
-flow exceeds volume of the channel
-Velocity (capacity and competence) increase
-Water leaves channel and immerses adjacent land
-Moving water and debris scour flood plains
-Water slows away from the river
Tropical rains on the Indian Subcontinent
-Large rains and severe flooding
-Many live in floodplain and delta plains
-1990, Bangladesh...100,000 dead
Rapid water rise with little warning
From unusual intense rainfall or dam failure
-Typified by rapid moving wall of debris laden water
Case History: Mississipii and Missouri Rivers
1993- jet stream high altitude winder current drifted southward
-Trapped moist, humid air from Gulf.
-Air rose and cooled releasing torrents of rain (years worth)
-Entered two rivers, flooded
-50 dead, 250,000 no drinking water, houses covered silt, 55,000 homes destroyed
Ice Age Megafloods
11 thousand years ago, ice dams failed
-Glacial Lake Missoula
-Scarred eastern Washington
-Created Channeled Scablands of Washington
-barren craggy, stripped rock
Living with Floods
Flood control is expensive and sometimes trivial
-Dams on tributaries hold back water from trunk stream
-Fake levees and flood walls increase channel volume
Living with Floods
People living in floodplains have danger
-Flood risks for insurance, home ownders, lenders, gov agencies
Hydrologic data is used to measure this
There are maps regulating areas to manage risks
Building in floodplains strictly regulated
likelihood that a flood of a given size or larger will happen at a specified locality during any given year
Cities cover large areas with impermeable concrete
-Stream water runoff from cities destructive
-shorter lag time between rainfall and flood flow
-large discharges for shorter duratiosn
-Water does not go in ground but floods
Turning some rivers into deadly cesspools
Raw sewage and drainage from urban areas
-Fertilizers, industrial sites, animal waste
Resevoirs make irrigation and hydroelectric power
Alter ecosystems, barriers to fish, decreased nutrients downstream, removing delta sediment source
What are Artesian ground-water systems characterized by?
rise of water above the level of a confined aquifer if a well is drilled into the aquifer
the volume of ground water flowing in a specified amount of time is proportional to the vertical drop in the height of the water table between two points divided by the horizontal distance between the two points
Stalactites and stalagmites
form as drops of water from the ceiling of a cave, lose dissolved carbon dioxide by entering into the cave with the atmospheric air
If an excessive pumping of ground water in a coastal area lowers the water table at a locality by 0.5 meter, what will the contact btw. the fresh ground water and the salty ground water in the locality do?
rise by 20 meters
What caused the leaning of the Pisa Tower in Italy?
consolidation of the ground material by rapid ground water depletion