Geology 107 Exam 2 Study Guide

What is Hydrologic Cycle?

∙ Hydrologic Cycle

o Distribution of Earth’s Water

 Oceans: 97.2%  

 Glaciers and Ice: 2.15%

 Groundwater: 0.63%

 Lakes & Rivers: 0.010%

 Inland Seas and Saline Lakes: 0.008%

 Atmosphere: 0.001%

 Biosphere: 0.0001%

 99.35% of Earth’s water is not a significant source of  freshwater, which is the water we use for drinking,  

agriculture, and industry

o Hydrological cycle: the movement of water through Earth’s  reservoirs  

 Reservoirs: ocean, atmosphere, lakes/rivers/streams

 Major processes

∙    Evaporation: water changing from liquid to gas  

(water vapor) by the sun’s heat 

o Over ocean’s surface, there is more  

evaporation than precipitation

∙    Condensation: water changing from gas to liquid,  

due to water vapor rising into Earth’s lowermost  

What is Watershed?

atmospheric layer (troposphere) and being cooled 

o Forms clouds

∙ Precipitation: condensed water vapor in troposphere falling back to Earth’s surface as rain and snow

o Over land’s surface, there’s more precipitation

than evaporation (even though there’s still  

much more evaporation and precipitation over  

the oceans, these numbers are relative)

∙ Surface Runoff: water flowing down a land surface  

into oceans

o Excess precipitation over land running off into  

oceans is equivalent to excess amount of  

evaporation over oceans, keeping water levels  

in the oceans normal

∙ Rivers and Streams

o Watershed (drainage basin): area over which precipitation  would be drained by rivers in that basin, if it were to fall  Drainage divide separates watersheds

 Within watersheds, rivers and streams can flow in  

What are Floodplains?

different patterns:

∙ Dendritic: tributaries flow into one main channel

Geology 107 Exam 2 Study Guide

o Created when rivers and streams flow through Don't forget about the age old question of What is a harmonious state?

the same rock type Don't forget about the age old question of How many significant figures are contained in each of the following measurements?

∙ Radial: rivers/streams flow away from a central  uplift  

o Created when there is a central high point  Don't forget about the age old question of what is Negative relationship in mathematics?

(imagine the tip of a pyramid), like a volcano

∙ Rectangular: rivers/streams bend at nearly right  angles

o Created when rivers/streams flow along  

joints/fractures in rocks

∙ Trellis: rivers and tributaries flow parallel to each  other for long distances

o Created when rivers flow in the valleys of  

folded rocks

o Longitudinal Profile & Gradient

 Longitudinal profile: plot of elevation of river from head  (source) to mouth (end) We also discuss several other topics like What are the three factors of production?

∙ Gradient: change in elevation as function of distance from head (source) to mouth (end of river)

o Gradient decreases from head to mouth

o Gradient = (elevation 1 – elevation 2) ÷  We also discuss several other topics like what is Europe’s climate?

distance

∙ Discharge: amount of water flowing past given point in given amount of time

o Discharge increases from head to mouth

∙ Competing Gradient and Discharge

o The higher/steeper the gradient, the faster the

river/stream velocity; since gradient decreases

downstream impact on velocity is to decrease

o Higher the discharge, faster the river/stream  

velocity; since discharge increases from head  

to mouth impact on velocity is to increase

o Factors (gradient decreasing, discharge  

increasing) “compete” in terms of impact on  

velocity from head to mouth

o Near head: high gradient is more important  

factor; velocity is relatively high We also discuss several other topics like As presented in class, what are the two most important performance decisions?

o Near mouth: high discharge is more important

factor; velocity of stream is relatively high

∙ Competence and Capacity

o We care about the velocity because it impacts  

competence of the river/stream

Geology 107 Exam 2 Study Guide

 Competence: maximum grain size that  

the transport agent (water) can carry as  

a suspended load; higher the velocity,  

higher the competence

o Rivers/streams carry weathered rock material  

in three major ways:

 1. Bed and saltation load (along bottom  

or bouncing along bottom)

 2. Suspended load (flowing along with  

water)

 3. Dissolved load (dissolved in water)

o We care about discharge because it impacts  

capacity of river/stream

 Capacity: maximum amount of material  

that transport agent (water) can carry as

a suspended load; higher the discharge,  

higher the capacity

o Floodplains and Meanders

 Floodplains: area over which river/stream meanders; can  be covered during a flood

 Meanders: bends or curves in river/stream; water  velocities are lower on inside of meander and higher on  outside of meander  

∙ Inside of meanders: lower velocity, lower  

competence, deposition occurs

o Deposits called point bars

∙ Outside of meanders: higher velocity, higher  

competence, erosion occurs, can form ox-bow lakes  (abandoned meanders)

 Deltas: deposits that occur when river/stream flows into  standing body of water; velocity of river/stream is  

decreased to zero

 Alluvial Fans: deposits that occur when sudden decrease  in gradient of river/steam occurs

 *water is the most important transport agent* *ice is the  best transport agent*

o Floods

 Flood: when a river/stream overflows its banks

∙ Natural levees: deposits that occur along banks of  river/stream created during floods when  

river/stream overflows its banks; velocity decreases  outside of channel, lower competence

Geology 107 Exam 2 Study Guide

 Common event; occurs yearly to every 2-3 years

∙ During the 2-3 year cycle, most of the erosion and  

transport occurs

∙ X-year flood: only once in the next x years will a  

flood with discharge equal to, or greater than, that  

flood occur again (probable, not certain)

o X-year floods are called recurrence interval:  

determined by measuring maximum discharge  

from river’s floods over long period of time

∙ Groundwater

o Water flowing beneath land surface

o Most abundant freshwater resource

o Flows slowly (cm or inches /day) in a direction determined by  changes in hydraulic head (water pressure relative to elevation  of land surface), from high to low head

 Doesn’t always flow downhill

o Water flow depends on two factors:

 Porosity: measure of amount of void spaces in material (%)  Permeability: measure of “interconnectedness” of void  spaces in material

o How Groundwater Moves

 Aquifers: material through which water can easily flow  (ex. Sandstone—high porosity and permeability  

∙ Unconfined aquifer: receives water from earth’s  

surface; characterized by zones of aeration (pores  

filled with air or partially filled with water/air) and  

zone of saturation (pores filled with water)

o Water can easily flow into it

o Water table: boundary between zone of  

aeration and zone of saturation

 Dynamic: can move up and down  

depending on availability of water

 Perched aquifer: due to lens of  

sediments acting as an aquiclude,

Geology 107 Exam 2 Study Guide

secondary water table is located above  

water table

 Aquicludes: material through which water cannot easily  flow (ex. Shale—low permeability)

o Well: where groundwater is brought to surface

 Cone of depression: local lowering of water table around  well due to removal (pumping) of groundwater to surface  Artesian wells: groundwater comes to surface without  having to pump

∙ Conditions:

o Confined aquifer: aquifer between two  

aquicludes

o Confined aquifer is inclined

o Recharge area above height of well  

o Groundwater & Limestone

 If it encounters limestone (calcite), groundwater flowing  through subsurface will leach (dissolve away) rock,  forming caves

∙ Stalactites: deposits formed on the top of caves

∙ Stalagmites: deposits formed on the floor of caves

Geology 107 Exam 2 Study Guide

∙ Sinkholes: collapse above where limestone has  

dissolved away  

 Karst topography: formed in areas dominated by  

limestones where large amounts of leaching (dissolution)  occur; characterized by irregular-shaped mountains with  intervening valleys

o Salt-Water Encroachment

 Along coastlines where groundwater is withdrawn from  wells; saltwater replaces fresh water and contaminates  wells

o Groundwater Contamination

 Types/Sources

∙ Landfills

∙ Septic tanks

∙ Mine Waste

∙ Waste Lagoons

∙ Chemical (gas) storage tanks

∙ Fertilizers

∙ Pesticides

∙ Salts on roads

 Potable water: drinkable with low risk of harm

 Dissolved materials (including contaminants) are typically  measured in water in concentrations of parts per million  (ppm) or parts per billion (ppb)

 Some concentrations must be quite low for contaminants  not to harm human health

∙ Polychlorinated biphenyls (PCBs) >5 ppb harmful

∙ Trichloroethylene (TCE) >0.005 ppm harmful

∙ Nitrates >10 ppm harmful

 6 Major Categories Defined by Environmental Protection  Agency (EPA)

∙ Microorganisms

∙ Disinfectants

∙ Disinfection Byproducts

∙ Inorganic Chemicals

∙ Organic Chemicals

∙ Radionuclides

∙ Glaciers

o Large masses of ice moving downhill under influence of gravity  Move at average rates of 1 meter/day; can surge and move much faster (several meters/day)

o Presently, glacial ice covers 10% of earth’s surface

Geology 107 Exam 2 Study Guide

o Two major types

 Continental glaciers: cover large continental areas ∙ Ex. Antarctica, Greenland

 Valley glaciers: cover mountainous areas (flow within  valleys)

o Ice as Transport Agent

 Glacial ice is by far the best transport agent

∙ Competence (can carry very large grains) and  

capacity (can carry a lot of material) are huge

o Glacial Erosional Features

 Glacial ice moving downhill erodes large amounts of rock   Types:

∙ U-shaped valleys

∙ Cirques: bowl-shaped depression, located at source  area of glacier

o Tarns: cirques filled with water

∙ Horns: triangular to pyramidal-shaped mountain  peaks caused by glacial erosion on all sides

∙ Aretes: sharp, razor-edge (steep slope; very rapid  change in elevation) ridges of rock caused by glacial erosion

∙ Hanging valleys: elevated glacial valleys where  

former glacier tributaries entered main glacial  

valley

∙ Fjords: glacial valleys flooded by seawater

∙ Glacial striations: scratches and grooves gouged in  rocks as ice passes

o Glacial Depositional Features

 When glacial ice stops advancing, deposits rock material  that was transported

 Categories of deposits

∙ Drift: all sediment of glacial origin found anywhere  on land or seafloor; general category

o Till: drift deposit from melting of ice,  

heterogeneous mixture of particle sizes, not  

layered by grain size

 Moraines: ridges of till

∙ Lateral moraine: till along side of  

glacial valley

∙ Medial moraine: formed where two

glacial valleys are joined, occur  

within ice of glacier

Geology 107 Exam 2 Study Guide

∙ End moraine: till deposit where  

glacier stopped and began to melt

∙ Terminal moraine: end moraine  

that marks furthest position of  

glacial advance

∙ Ground moraine: random till

o Outwash: drift deposits from meltwater  

flowing away from glaciers, layered by grain  

size (big on bottom, small on top)

 Features

∙ Drumlins: smooth, elongated rides of till, orientation tells direction of ice movement

∙ Eskers: sinuous ridges of sand and gravel—

deposited by glacial meltwater flowing beneath ice ∙ Kettles (Kettle Lakes): depressions, created by  

isolated block of ice that melt after main glacier has  retreated

∙ Varves: cyclical layers of sediment deposited on  seasonal basis (two per year) in glacial lakes

o Silt and fine sand deposited late spring and  

summer from sediment load from meltwater

o Clay deposited from suspended load during  

winter months when meltwater is reduce and  

lake surface freezes

o Pleistocene Ice Age

 During last 2 million years, Earth’s climate has been  relatively cold; globally cold enough that glacial ice could  grow

 Glacial Time Periods

∙ Within Ice Ages, periods of time when its  

significantly colder (glacial ice grow)

∙ 10s to 100s of thousands of years

∙ During these glacial time periods, surface runoff  decreases (water tied up in ice); global sea level  

decreases (up to 40m/120 ft. lower 10,000 years  

ago)

 Interglacial Time Periods

∙ Within Ice Ages, periods of time when its  

significantly warmer (glacial ice melts)

∙ 10s to 100s of thousands of years

∙ Surface runoff increases (water tied up in ice melts  and returns to oceans) and warmer oceans expand,

Geology 107 Exam 2 Study Guide

increasing volume; global sea level increases (up to  8m/ 24 ft. higher 120,000 years ago)

 Ice Ages

∙ Climate variations resulting in globally warmer and  colder temperatures have occurred throughout  earth’s history

 Causes of Ice Ages & Glacial/Interglacial Time Periods ∙ Climatic variations due to two major processes: o Longer term fluctuations due to plate tectonics  Based on two fundamental principles:

∙ Outer shell of earth divided into  

series of 12 or so individual  

lithospheric plates

∙ Plates are in motion with respect  

to one another (relative motion)  

and with respect to underlying  

lower mantle (absolute motion)

o Only move at velocities of 2-

16 cm/year

 Movements of plates and their  

interactions can dramatically influence  

climate; happen very slowly, but over  

long periods of time, can have major  

impacts

o Shorter term fluctuations due to variations in  earth’ s orbit and rotational axis with respect  

to sun (Milankovitch cycles)

 Milankovitch Cycles: Short-Term  

Changes in Climate

∙ Changes in earth’s revolution  

about sun and changes in earth’s  

rotational axis

∙ Three major Milankovitch cycles:

o Changes in eccentricity:  

earth’s revolution about the  

sun

 Over a period of about  

100,000 years; Earth’s  

revolution about sun  

becomes more/less  

elliptical

 Changes amount of  

solar radiation

Geology 107 Exam 2 Study Guide

reaching earth from  

sun

o Changes in obliquity: earth’s  

rotational axis with respect  

to sun

 Over time periods of  

40,000 years; Earth’s  

angle of obliquity  

varies between 22.5  

and 24.5 degrees

 Changes intensity of  

solar radiation  

reaching earth from  

sun

o Precession: earth’s rotational

axis

 Over periods of 20,000  

years; earth’s  

rotational axis  

precesses

 Changes intensity of  

solar radiation  

reaching earth from  

sun

∙ Together these cycles acting over  

10’s to 100’s of thousands of years  

can produce changes in Earth’s  

climate (glacial/interglacial time  

periods)

o Changes in eccentricity,  

obliquity, and precession  

occur at the same time, but  

over different lengths of time

o Sum together to change  

climate over time periods on  

order of 10’s to 100’s of  

thousands of years

∙ Present-Day Global Warming: Human Impact

o Over past 10,000 years, evidence for “natural” warming signal  and, in past 150 years, human-induced signal

o Global temperatures since 1880 are increasing

 Due to enhanced greenhouse effect

Geology 107 Exam 2 Study Guide

 Greenhouse gases in earth’s atmosphere absorb heat from solar radiation that has reflected off Earth’s surface, keeps heat in atmosphere

 Reflected solar radiation slightly longer wavelength than  visible light—infrared waves

∙ Major greenhouse gases in atmosphere absorbing  

infrared waves are water vapor, carbon dioxide,  

methane (CH4), nitrous oxide (N2O) and ozone (O3)

o Human Impact on Carbon Cycle

 Increasing levels of carbon dioxide and methane in earth’s atmosphere; enhanced greenhouse effect

∙ Due primarily to increased burning of fossil fuels  

(gasoline, oil, coal) releasing carbon dioxide into  

atmosphere

∙ Deforestation and increased methane due to  

agricultural and fossil fuel product also contribute to

greenhouse effect

o Impacts of Human Enhanced Global Warming: Globally Higher  Sea Level

 Melting glaciers increase surface runoff to oceans,  

warming oceans, expansion of salt water

 About 70% of world’s population lives within 100 km of a  coastline

 Oceanic current circulation affected

 Marine organisms affected

o Changes to Climatic Patterns

 Some areas warmer or cooler, some areas wetter or drier  Could dramatically impact agricultural production  

necessity to feed growing human population

∙ Wind

o Wind: horizontal movements of air

o Eolian features: erosional and depositional, formed by wind  Mostly clearly identifiable in desert areas

o Deserts: areas with average annual precipitation of less than  250 mm (10 in) per year, or areas where more water is lost by  evaporation and transportation than what falls as precipitation o Deserts

 Most deserts created by two major factors:

∙ Worldwide wind circulation patterns: create regions  with low precipitation; subtropical high pressure  

zones

∙ Topographic rain shadow effects: precipitation falls  

on one side of mountain range; opposite side is arid

Geology 107 Exam 2 Study Guide

o Wind as a Transport Agent

 Wind is the least effective transport agent; competence  and capacity are small

 Only at high wind spends (over 100 km/hr) is the  competence of wind high; the capacity of wind is only high for dust-sized particles

∙ Competence and capacity: ice > water > wind

∙ Ice is the “best” transport agent, but water is the  most important

o Wind Erosion

 Erodes material by two processes:

∙ Deflation: wind blows across surface removing  

smaller-sized (sand and dust-sized) particles; leaves  behind larger-sized particles

o Desert pavement: deflation feature where  

surface layer is primarily formed of larger

sized particles

∙ Abrasion (sandblasting): sand moves across surface  eroding it away

o Ventifacts: features formed by abrasion

o Wind Deposits

 When wind slows down, competence is lower and it  deposits what it is carrying

 Two major wind deposits:

∙ Loess: dust-sized particles

∙ Dunes: sand-sized particles

o Barchan Dunes: solitary, crescent-shaped, tips  

point downwind, limited sand supply, little  

vegetation, constant wind direction

o Transverse Dunes: long, wavy ridges that lie  

transverse (perpendicular) to wind, lots of  

sand, moderate velocity winds, limited  

vegetation

o Longitudinal Dunes: long, straight edges,  

parallel with wind direction, formed by steady,  

high velocity winds, moderate sand supply,  

limited vegetation

o Star Dunes: mound of sand having high  

central point with three or four ridges  

radiating outward from centers, occurs in  

regions with winds from many directions

o Parabolic Dunes: look like barchan dunes in  

reverse, tips point upwind, common in coastal

Geology 107 Exam 2 Study Guide

areas, vegetation anchors tips, center is  

eroded

o Desertification: extreme deterioration of land in arid and sub humid areas due to loss of vegetation and soil moisture

 Results mainly from human activities and influenced by  variations in climate

 Can be caused by overgrazing, overuse of groundwater,  and diversion of water from rivers for human use

∙ Oceans and Waves

o The Oceans

 Four major ocean basins: Pacific, Atlantic, Indian, Arctic ∙ Pacific is the largest ocean, covering over 1/3 of  

Earth’s surface  

 Salinity

∙ Seawater is composed of water and dissolved  

materials (mainly salts)

∙ Measure of the amount of dissolved materials

∙ Expressed in parts per thousand

o Average salinity in oceans is 35 parts per  

thousand (ppt), meaning 965 parts are water  

and 35 parts are dissolved salts

∙ Major dissolved materials in seawater:

o 1. Chloride (Cl-)—55%

o 2. Sodium (Na+)—31%

o 3. Sulfate (SO42-)—8%

o 4. Magnesium (Mg2+)—4%

o 5. Calcium (Ca2+)—1%

o 6. Potassium (K+)—1%

∙ Primary source for dissolved materials are rocks on  

land which are weathered and transported via water

to the oceans

o Waves

 Waves in oceans are displacements of seawater at/near  ocean surface

 Generated by winds (horizontal movement of air) blowing  across oceans

 Fundamental Characteristics of Waves

∙ Wave height: displacement between peak and trough of wave

∙ Wave length: distance traveled during one cycle of  

wave

∙ Wave period: time that it takes to complete one cycle of wave

Geology 107 Exam 2 Study Guide

 Fundamental Characteristics depend on three major wind  factors:

∙ Wind speed: higher wind speed creates greater  wave height

∙ Length of time that wind blows: longer time creates  greater wave length, wave period, and wave height  (all 3)

∙ Fetch: distance of open water over which winds can  blow; greater fetch creates greater wave length,  wave period, and wave height (all 3)

 Ocean waves move by displacing water particles ∙ In open ocean, where depths are greater than half  the wave length of the wave, oceans displace water  in roughly circular orbits as waves move past,  occurs down to depths less than half the wave  length of the wave

 What causes water to  break at shoreline?

∙ As waves approach shoreline, series of events occur  that cause waves to break  

o 1. As waves approach shoreline, water depths  decrease

o 2. When depths are less than ½ wave length of wave, ocean bottom begins to interfere with  

circular motion of water particles

o 3. Interference causes circular motion to  

change to more elliptical motion

o 4. This elliptical motion results in wave  

slowing down (velocity decreases)

o 5. When wave slows down, height increases

Geology 107 Exam 2 Study Guide

o 6. When wave height becomes too high, wave  

can no longer support its weight and it breaks

 Wave Refraction

∙ In areas where water depth varies along coastline,  

waves refract (or curve) as they approach shoreline

o Move faster in deeper areas, slower in  

shallower areas

∙ Focuses energy toward shallower areas (headlands= more erosion by waves) and away from deeper areas

(embayments= less erosion by waves)

 Longshore Currents  

∙ Waves don’t always approach parallel to coastline  

(wind direction not perpendicular to coastline)

∙ Causes component of wave as it breaks to be  

parallel to coastline—movement of water parallel to  

coastline is called longshore current

 Longshore Drift

∙ Sediment carried by longshore current is called  

longshore (beach) drift

 Rip Currents

∙ In areas where longshore currents occur, rip  

currents may also be present

∙ Flow from shoreline out to ocean

∙ May be quite strong; danger to swimmers

∙ Coastal Features and Tides

o Coastal Features

 Coral Reefs

∙ Characteristic of coastlines in warm climates

∙ Precipitates of calcium and carbonate (calcite)

 Coastlines

∙ Two major types of coastlines, those dominated by  

depositional processes (sediment-rich coastlines)  

and those dominated by erosional processes  

(sediment-poor coastlines)

o Sediment-Poor Coastlines

 Wave-Cut Platform: nearly horizontal  

surface extending from beneath wave

cut cliff toward ocean

 Sea Arch: arch (hollowed out area)  

formed in headland by wave erosion

 Sea Stack: formed after collapse of sea  

arch

 Beach: shoreline accumulation of sand

Geology 107 Exam 2 Study Guide

 Spit: beach extended from mainland  

across bay due to longshore drift

 Baymouth Bar: spit that extends all the  

way across a bay

 Barrier Island: long, offshore islands of  

sediment (mostly sand) that trend  

parallel to mainland shore

 Estuaries: semi-enclosed coastal bodies  

of water that have free connection with  

ocean and have water that is less saline  

than oceans and more saline than  

freshwater

∙ Ex. Delaware Bay/River System

o “Drowned” river valley  

estuary

o During time periods of lower  

global sea level, large areas  

of bay were land surfaces

o Ancestral Delaware River  

flowed across this land in  

paleo-channels

o At present with higher global

sea level, the bay is now  

“flooded” with seawater

o Tides

 Locally higher/lower levels of ocean surface

 Primarily caused by gravitational attraction that Moon  exerts on Earth and by effect of centrifugal forces on  Earth/moon system

 Locations experience 1-2 high tides and 1-2 low tides per  day

 There are also tidal variations generated due to Sun’s  gravitational attraction acting to reinforce or reduce  moon’s gravitational attraction on Earth

∙ Spring Tides

o Tidal variation (reach) is higher

o High tides are higher, low tides are lower

o Occur during new moon and full moon lunar  

phases

∙ Neap Tides

o Tidal variation (reach) is lower

o High tides are lower and low tides are higher

Geology 107 Exam 2 Study Guide

o Occur during 1st and 3rd quarter moon lunar  phases

Geology 107 Exam 2 Study Guide

∙ Hydrologic Cycle

o Distribution of Earth’s Water

 Oceans: 97.2%  

 Glaciers and Ice: 2.15%

 Groundwater: 0.63%

 Lakes & Rivers: 0.010%

 Inland Seas and Saline Lakes: 0.008%

 Atmosphere: 0.001%

 Biosphere: 0.0001%

 99.35% of Earth’s water is not a significant source of  freshwater, which is the water we use for drinking,  

agriculture, and industry

o Hydrological cycle: the movement of water through Earth’s  reservoirs  

 Reservoirs: ocean, atmosphere, lakes/rivers/streams

 Major processes

∙    Evaporation: water changing from liquid to gas  

(water vapor) by the sun’s heat 

o Over ocean’s surface, there is more  

evaporation than precipitation

∙    Condensation: water changing from gas to liquid,  

due to water vapor rising into Earth’s lowermost  

atmospheric layer (troposphere) and being cooled 

o Forms clouds

∙ Precipitation: condensed water vapor in troposphere falling back to Earth’s surface as rain and snow

o Over land’s surface, there’s more precipitation

than evaporation (even though there’s still  

much more evaporation and precipitation over  

the oceans, these numbers are relative)

∙ Surface Runoff: water flowing down a land surface  

into oceans

o Excess precipitation over land running off into  

oceans is equivalent to excess amount of  

evaporation over oceans, keeping water levels  

in the oceans normal

∙ Rivers and Streams

o Watershed (drainage basin): area over which precipitation  would be drained by rivers in that basin, if it were to fall  Drainage divide separates watersheds

 Within watersheds, rivers and streams can flow in  

different patterns:

∙ Dendritic: tributaries flow into one main channel

Geology 107 Exam 2 Study Guide

o Created when rivers and streams flow through

the same rock type

∙ Radial: rivers/streams flow away from a central  uplift  

o Created when there is a central high point  

(imagine the tip of a pyramid), like a volcano

∙ Rectangular: rivers/streams bend at nearly right  angles

o Created when rivers/streams flow along  

joints/fractures in rocks

∙ Trellis: rivers and tributaries flow parallel to each  other for long distances

o Created when rivers flow in the valleys of  

folded rocks

o Longitudinal Profile & Gradient

 Longitudinal profile: plot of elevation of river from head  (source) to mouth (end)

∙ Gradient: change in elevation as function of distance from head (source) to mouth (end of river)

o Gradient decreases from head to mouth

o Gradient = (elevation 1 – elevation 2) ÷  

distance

∙ Discharge: amount of water flowing past given point in given amount of time

o Discharge increases from head to mouth

∙ Competing Gradient and Discharge

o The higher/steeper the gradient, the faster the

river/stream velocity; since gradient decreases

downstream impact on velocity is to decrease

o Higher the discharge, faster the river/stream  

velocity; since discharge increases from head  

to mouth impact on velocity is to increase

o Factors (gradient decreasing, discharge  

increasing) “compete” in terms of impact on  

velocity from head to mouth

o Near head: high gradient is more important  

factor; velocity is relatively high

o Near mouth: high discharge is more important

factor; velocity of stream is relatively high

∙ Competence and Capacity

o We care about the velocity because it impacts  

competence of the river/stream

Geology 107 Exam 2 Study Guide

 Competence: maximum grain size that  

the transport agent (water) can carry as  

a suspended load; higher the velocity,  

higher the competence

o Rivers/streams carry weathered rock material  

in three major ways:

 1. Bed and saltation load (along bottom  

or bouncing along bottom)

 2. Suspended load (flowing along with  

water)

 3. Dissolved load (dissolved in water)

o We care about discharge because it impacts  

capacity of river/stream

 Capacity: maximum amount of material  

that transport agent (water) can carry as

a suspended load; higher the discharge,  

higher the capacity

o Floodplains and Meanders

 Floodplains: area over which river/stream meanders; can  be covered during a flood

 Meanders: bends or curves in river/stream; water  velocities are lower on inside of meander and higher on  outside of meander  

∙ Inside of meanders: lower velocity, lower  

competence, deposition occurs

o Deposits called point bars

∙ Outside of meanders: higher velocity, higher  

competence, erosion occurs, can form ox-bow lakes  (abandoned meanders)

 Deltas: deposits that occur when river/stream flows into  standing body of water; velocity of river/stream is  

decreased to zero

 Alluvial Fans: deposits that occur when sudden decrease  in gradient of river/steam occurs

 *water is the most important transport agent* *ice is the  best transport agent*

o Floods

 Flood: when a river/stream overflows its banks

∙ Natural levees: deposits that occur along banks of  river/stream created during floods when  

river/stream overflows its banks; velocity decreases  outside of channel, lower competence

Geology 107 Exam 2 Study Guide

 Common event; occurs yearly to every 2-3 years

∙ During the 2-3 year cycle, most of the erosion and  

transport occurs

∙ X-year flood: only once in the next x years will a  

flood with discharge equal to, or greater than, that  

flood occur again (probable, not certain)

o X-year floods are called recurrence interval:  

determined by measuring maximum discharge  

from river’s floods over long period of time

∙ Groundwater

o Water flowing beneath land surface

o Most abundant freshwater resource

o Flows slowly (cm or inches /day) in a direction determined by  changes in hydraulic head (water pressure relative to elevation  of land surface), from high to low head

 Doesn’t always flow downhill

o Water flow depends on two factors:

 Porosity: measure of amount of void spaces in material (%)  Permeability: measure of “interconnectedness” of void  spaces in material

o How Groundwater Moves

 Aquifers: material through which water can easily flow  (ex. Sandstone—high porosity and permeability  

∙ Unconfined aquifer: receives water from earth’s  

surface; characterized by zones of aeration (pores  

filled with air or partially filled with water/air) and  

zone of saturation (pores filled with water)

o Water can easily flow into it

o Water table: boundary between zone of  

aeration and zone of saturation

 Dynamic: can move up and down  

depending on availability of water

 Perched aquifer: due to lens of  

sediments acting as an aquiclude,

Geology 107 Exam 2 Study Guide

secondary water table is located above  

water table

 Aquicludes: material through which water cannot easily  flow (ex. Shale—low permeability)

o Well: where groundwater is brought to surface

 Cone of depression: local lowering of water table around  well due to removal (pumping) of groundwater to surface  Artesian wells: groundwater comes to surface without  having to pump

∙ Conditions:

o Confined aquifer: aquifer between two  

aquicludes

o Confined aquifer is inclined

o Recharge area above height of well  

o Groundwater & Limestone

 If it encounters limestone (calcite), groundwater flowing  through subsurface will leach (dissolve away) rock,  forming caves

∙ Stalactites: deposits formed on the top of caves

∙ Stalagmites: deposits formed on the floor of caves

Geology 107 Exam 2 Study Guide

∙ Sinkholes: collapse above where limestone has  

dissolved away  

 Karst topography: formed in areas dominated by  

limestones where large amounts of leaching (dissolution)  occur; characterized by irregular-shaped mountains with  intervening valleys

o Salt-Water Encroachment

 Along coastlines where groundwater is withdrawn from  wells; saltwater replaces fresh water and contaminates  wells

o Groundwater Contamination

 Types/Sources

∙ Landfills

∙ Septic tanks

∙ Mine Waste

∙ Waste Lagoons

∙ Chemical (gas) storage tanks

∙ Fertilizers

∙ Pesticides

∙ Salts on roads

 Potable water: drinkable with low risk of harm

 Dissolved materials (including contaminants) are typically  measured in water in concentrations of parts per million  (ppm) or parts per billion (ppb)

 Some concentrations must be quite low for contaminants  not to harm human health

∙ Polychlorinated biphenyls (PCBs) >5 ppb harmful

∙ Trichloroethylene (TCE) >0.005 ppm harmful

∙ Nitrates >10 ppm harmful

 6 Major Categories Defined by Environmental Protection  Agency (EPA)

∙ Microorganisms

∙ Disinfectants

∙ Disinfection Byproducts

∙ Inorganic Chemicals

∙ Organic Chemicals

∙ Radionuclides

∙ Glaciers

o Large masses of ice moving downhill under influence of gravity  Move at average rates of 1 meter/day; can surge and move much faster (several meters/day)

o Presently, glacial ice covers 10% of earth’s surface

Geology 107 Exam 2 Study Guide

o Two major types

 Continental glaciers: cover large continental areas ∙ Ex. Antarctica, Greenland

 Valley glaciers: cover mountainous areas (flow within  valleys)

o Ice as Transport Agent

 Glacial ice is by far the best transport agent

∙ Competence (can carry very large grains) and  

capacity (can carry a lot of material) are huge

o Glacial Erosional Features

 Glacial ice moving downhill erodes large amounts of rock   Types:

∙ U-shaped valleys

∙ Cirques: bowl-shaped depression, located at source  area of glacier

o Tarns: cirques filled with water

∙ Horns: triangular to pyramidal-shaped mountain  peaks caused by glacial erosion on all sides

∙ Aretes: sharp, razor-edge (steep slope; very rapid  change in elevation) ridges of rock caused by glacial erosion

∙ Hanging valleys: elevated glacial valleys where  

former glacier tributaries entered main glacial  

valley

∙ Fjords: glacial valleys flooded by seawater

∙ Glacial striations: scratches and grooves gouged in  rocks as ice passes

o Glacial Depositional Features

 When glacial ice stops advancing, deposits rock material  that was transported

 Categories of deposits

∙ Drift: all sediment of glacial origin found anywhere  on land or seafloor; general category

o Till: drift deposit from melting of ice,  

heterogeneous mixture of particle sizes, not  

layered by grain size

 Moraines: ridges of till

∙ Lateral moraine: till along side of  

glacial valley

∙ Medial moraine: formed where two

glacial valleys are joined, occur  

within ice of glacier

Geology 107 Exam 2 Study Guide

∙ End moraine: till deposit where  

glacier stopped and began to melt

∙ Terminal moraine: end moraine  

that marks furthest position of  

glacial advance

∙ Ground moraine: random till

o Outwash: drift deposits from meltwater  

flowing away from glaciers, layered by grain  

size (big on bottom, small on top)

 Features

∙ Drumlins: smooth, elongated rides of till, orientation tells direction of ice movement

∙ Eskers: sinuous ridges of sand and gravel—

deposited by glacial meltwater flowing beneath ice ∙ Kettles (Kettle Lakes): depressions, created by  

isolated block of ice that melt after main glacier has  retreated

∙ Varves: cyclical layers of sediment deposited on  seasonal basis (two per year) in glacial lakes

o Silt and fine sand deposited late spring and  

summer from sediment load from meltwater

o Clay deposited from suspended load during  

winter months when meltwater is reduce and  

lake surface freezes

o Pleistocene Ice Age

 During last 2 million years, Earth’s climate has been  relatively cold; globally cold enough that glacial ice could  grow

 Glacial Time Periods

∙ Within Ice Ages, periods of time when its  

significantly colder (glacial ice grow)

∙ 10s to 100s of thousands of years

∙ During these glacial time periods, surface runoff  decreases (water tied up in ice); global sea level  

decreases (up to 40m/120 ft. lower 10,000 years  

ago)

 Interglacial Time Periods

∙ Within Ice Ages, periods of time when its  

significantly warmer (glacial ice melts)

∙ 10s to 100s of thousands of years

∙ Surface runoff increases (water tied up in ice melts  and returns to oceans) and warmer oceans expand,

Geology 107 Exam 2 Study Guide

increasing volume; global sea level increases (up to  8m/ 24 ft. higher 120,000 years ago)

 Ice Ages

∙ Climate variations resulting in globally warmer and  colder temperatures have occurred throughout  earth’s history

 Causes of Ice Ages & Glacial/Interglacial Time Periods ∙ Climatic variations due to two major processes: o Longer term fluctuations due to plate tectonics  Based on two fundamental principles:

∙ Outer shell of earth divided into  

series of 12 or so individual  

lithospheric plates

∙ Plates are in motion with respect  

to one another (relative motion)  

and with respect to underlying  

lower mantle (absolute motion)

o Only move at velocities of 2-

16 cm/year

 Movements of plates and their  

interactions can dramatically influence  

climate; happen very slowly, but over  

long periods of time, can have major  

impacts

o Shorter term fluctuations due to variations in  earth’ s orbit and rotational axis with respect  

to sun (Milankovitch cycles)

 Milankovitch Cycles: Short-Term  

Changes in Climate

∙ Changes in earth’s revolution  

about sun and changes in earth’s  

rotational axis

∙ Three major Milankovitch cycles:

o Changes in eccentricity:  

earth’s revolution about the  

sun

 Over a period of about  

100,000 years; Earth’s  

revolution about sun  

becomes more/less  

elliptical

 Changes amount of  

solar radiation

Geology 107 Exam 2 Study Guide

reaching earth from  

sun

o Changes in obliquity: earth’s  

rotational axis with respect  

to sun

 Over time periods of  

40,000 years; Earth’s  

angle of obliquity  

varies between 22.5  

and 24.5 degrees

 Changes intensity of  

solar radiation  

reaching earth from  

sun

o Precession: earth’s rotational

axis

 Over periods of 20,000  

years; earth’s  

rotational axis  

precesses

 Changes intensity of  

solar radiation  

reaching earth from  

sun

∙ Together these cycles acting over  

10’s to 100’s of thousands of years  

can produce changes in Earth’s  

climate (glacial/interglacial time  

periods)

o Changes in eccentricity,  

obliquity, and precession  

occur at the same time, but  

over different lengths of time

o Sum together to change  

climate over time periods on  

order of 10’s to 100’s of  

thousands of years

∙ Present-Day Global Warming: Human Impact

o Over past 10,000 years, evidence for “natural” warming signal  and, in past 150 years, human-induced signal

o Global temperatures since 1880 are increasing

 Due to enhanced greenhouse effect

Geology 107 Exam 2 Study Guide

 Greenhouse gases in earth’s atmosphere absorb heat from solar radiation that has reflected off Earth’s surface, keeps heat in atmosphere

 Reflected solar radiation slightly longer wavelength than  visible light—infrared waves

∙ Major greenhouse gases in atmosphere absorbing  

infrared waves are water vapor, carbon dioxide,  

methane (CH4), nitrous oxide (N2O) and ozone (O3)

o Human Impact on Carbon Cycle

 Increasing levels of carbon dioxide and methane in earth’s atmosphere; enhanced greenhouse effect

∙ Due primarily to increased burning of fossil fuels  

(gasoline, oil, coal) releasing carbon dioxide into  

atmosphere

∙ Deforestation and increased methane due to  

agricultural and fossil fuel product also contribute to

greenhouse effect

o Impacts of Human Enhanced Global Warming: Globally Higher  Sea Level

 Melting glaciers increase surface runoff to oceans,  

warming oceans, expansion of salt water

 About 70% of world’s population lives within 100 km of a  coastline

 Oceanic current circulation affected

 Marine organisms affected

o Changes to Climatic Patterns

 Some areas warmer or cooler, some areas wetter or drier  Could dramatically impact agricultural production  

necessity to feed growing human population

∙ Wind

o Wind: horizontal movements of air

o Eolian features: erosional and depositional, formed by wind  Mostly clearly identifiable in desert areas

o Deserts: areas with average annual precipitation of less than  250 mm (10 in) per year, or areas where more water is lost by  evaporation and transportation than what falls as precipitation o Deserts

 Most deserts created by two major factors:

∙ Worldwide wind circulation patterns: create regions  with low precipitation; subtropical high pressure  

zones

∙ Topographic rain shadow effects: precipitation falls  

on one side of mountain range; opposite side is arid

Geology 107 Exam 2 Study Guide

o Wind as a Transport Agent

 Wind is the least effective transport agent; competence  and capacity are small

 Only at high wind spends (over 100 km/hr) is the  competence of wind high; the capacity of wind is only high for dust-sized particles

∙ Competence and capacity: ice > water > wind

∙ Ice is the “best” transport agent, but water is the  most important

o Wind Erosion

 Erodes material by two processes:

∙ Deflation: wind blows across surface removing  

smaller-sized (sand and dust-sized) particles; leaves  behind larger-sized particles

o Desert pavement: deflation feature where  

surface layer is primarily formed of larger

sized particles

∙ Abrasion (sandblasting): sand moves across surface  eroding it away

o Ventifacts: features formed by abrasion

o Wind Deposits

 When wind slows down, competence is lower and it  deposits what it is carrying

 Two major wind deposits:

∙ Loess: dust-sized particles

∙ Dunes: sand-sized particles

o Barchan Dunes: solitary, crescent-shaped, tips  

point downwind, limited sand supply, little  

vegetation, constant wind direction

o Transverse Dunes: long, wavy ridges that lie  

transverse (perpendicular) to wind, lots of  

sand, moderate velocity winds, limited  

vegetation

o Longitudinal Dunes: long, straight edges,  

parallel with wind direction, formed by steady,  

high velocity winds, moderate sand supply,  

limited vegetation

o Star Dunes: mound of sand having high  

central point with three or four ridges  

radiating outward from centers, occurs in  

regions with winds from many directions

o Parabolic Dunes: look like barchan dunes in  

reverse, tips point upwind, common in coastal

Geology 107 Exam 2 Study Guide

areas, vegetation anchors tips, center is  

eroded

o Desertification: extreme deterioration of land in arid and sub humid areas due to loss of vegetation and soil moisture

 Results mainly from human activities and influenced by  variations in climate

 Can be caused by overgrazing, overuse of groundwater,  and diversion of water from rivers for human use

∙ Oceans and Waves

o The Oceans

 Four major ocean basins: Pacific, Atlantic, Indian, Arctic ∙ Pacific is the largest ocean, covering over 1/3 of  

Earth’s surface  

 Salinity

∙ Seawater is composed of water and dissolved  

materials (mainly salts)

∙ Measure of the amount of dissolved materials

∙ Expressed in parts per thousand

o Average salinity in oceans is 35 parts per  

thousand (ppt), meaning 965 parts are water  

and 35 parts are dissolved salts

∙ Major dissolved materials in seawater:

o 1. Chloride (Cl-)—55%

o 2. Sodium (Na+)—31%

o 3. Sulfate (SO42-)—8%

o 4. Magnesium (Mg2+)—4%

o 5. Calcium (Ca2+)—1%

o 6. Potassium (K+)—1%

∙ Primary source for dissolved materials are rocks on  

land which are weathered and transported via water

to the oceans

o Waves

 Waves in oceans are displacements of seawater at/near  ocean surface

 Generated by winds (horizontal movement of air) blowing  across oceans

 Fundamental Characteristics of Waves

∙ Wave height: displacement between peak and trough of wave

∙ Wave length: distance traveled during one cycle of  

wave

∙ Wave period: time that it takes to complete one cycle of wave

Geology 107 Exam 2 Study Guide

 Fundamental Characteristics depend on three major wind  factors:

∙ Wind speed: higher wind speed creates greater  wave height

∙ Length of time that wind blows: longer time creates  greater wave length, wave period, and wave height  (all 3)

∙ Fetch: distance of open water over which winds can  blow; greater fetch creates greater wave length,  wave period, and wave height (all 3)

 Ocean waves move by displacing water particles ∙ In open ocean, where depths are greater than half  the wave length of the wave, oceans displace water  in roughly circular orbits as waves move past,  occurs down to depths less than half the wave  length of the wave

 What causes water to  break at shoreline?

∙ As waves approach shoreline, series of events occur  that cause waves to break  

o 1. As waves approach shoreline, water depths  decrease

o 2. When depths are less than ½ wave length of wave, ocean bottom begins to interfere with  

circular motion of water particles

o 3. Interference causes circular motion to  

change to more elliptical motion

o 4. This elliptical motion results in wave  

slowing down (velocity decreases)

o 5. When wave slows down, height increases

Geology 107 Exam 2 Study Guide

o 6. When wave height becomes too high, wave  

can no longer support its weight and it breaks

 Wave Refraction

∙ In areas where water depth varies along coastline,  

waves refract (or curve) as they approach shoreline

o Move faster in deeper areas, slower in  

shallower areas

∙ Focuses energy toward shallower areas (headlands= more erosion by waves) and away from deeper areas

(embayments= less erosion by waves)

 Longshore Currents  

∙ Waves don’t always approach parallel to coastline  

(wind direction not perpendicular to coastline)

∙ Causes component of wave as it breaks to be  

parallel to coastline—movement of water parallel to  

coastline is called longshore current

 Longshore Drift

∙ Sediment carried by longshore current is called  

longshore (beach) drift

 Rip Currents

∙ In areas where longshore currents occur, rip  

currents may also be present

∙ Flow from shoreline out to ocean

∙ May be quite strong; danger to swimmers

∙ Coastal Features and Tides

o Coastal Features

 Coral Reefs

∙ Characteristic of coastlines in warm climates

∙ Precipitates of calcium and carbonate (calcite)

 Coastlines

∙ Two major types of coastlines, those dominated by  

depositional processes (sediment-rich coastlines)  

and those dominated by erosional processes  

(sediment-poor coastlines)

o Sediment-Poor Coastlines

 Wave-Cut Platform: nearly horizontal  

surface extending from beneath wave

cut cliff toward ocean

 Sea Arch: arch (hollowed out area)  

formed in headland by wave erosion

 Sea Stack: formed after collapse of sea  

arch

 Beach: shoreline accumulation of sand

Geology 107 Exam 2 Study Guide

 Spit: beach extended from mainland  

across bay due to longshore drift

 Baymouth Bar: spit that extends all the  

way across a bay

 Barrier Island: long, offshore islands of  

sediment (mostly sand) that trend  

parallel to mainland shore

 Estuaries: semi-enclosed coastal bodies  

of water that have free connection with  

ocean and have water that is less saline  

than oceans and more saline than  

freshwater

∙ Ex. Delaware Bay/River System

o “Drowned” river valley  

estuary

o During time periods of lower  

global sea level, large areas  

of bay were land surfaces

o Ancestral Delaware River  

flowed across this land in  

paleo-channels

o At present with higher global

sea level, the bay is now  

“flooded” with seawater

o Tides

 Locally higher/lower levels of ocean surface

 Primarily caused by gravitational attraction that Moon  exerts on Earth and by effect of centrifugal forces on  Earth/moon system

 Locations experience 1-2 high tides and 1-2 low tides per  day

 There are also tidal variations generated due to Sun’s  gravitational attraction acting to reinforce or reduce  moon’s gravitational attraction on Earth

∙ Spring Tides

o Tidal variation (reach) is higher

o High tides are higher, low tides are lower

o Occur during new moon and full moon lunar  

phases

∙ Neap Tides

o Tidal variation (reach) is lower

o High tides are lower and low tides are higher

Geology 107 Exam 2 Study Guide

o Occur during 1st and 3rd quarter moon lunar  phases