AI generated flash cards from notes
Scientific Method:
· Observe (why, how )
· Explain (define hypothesis)
- alternative hypothesis; Ha- “If A, then B”)
- Null hypothesis; Ho – no difference. “If A happens, there is no difference to B”
· Test (an experiment will not always prove a hypothesis)
· Refine
Four major categories:
1. Geology – Physical and Historical
2. Oceanography – 70% of Earth is water, mostly oceans
3. Meteorology – weather and atmosphere
4. Astronomy – earth’s place in the Universe
Earth’s Spheres:
· Hydrosphere – water portion of planet
· Atmosphere – gaseous portion of planet
· Biosphere – Totality of life – The one (topic) we will touch on the least
The system:
All spheres can be studied separately but that’s not
ideal, why?
– All related in a complex and continuously interacting whole
• Powering the system
– Sun
• Drives the external processes that occur in the
atmosphere, hydrosphere, and at the Earth’s surface
– Heat from Earth’s interior
• Powers internal processes that produce volcanoes,
earthquakes and mountains.
• People
– Actions cause changes in all parts
Resources & environmental issues:
• What does environmental refer to?
– Everything that surrounds and influences an
organism
• Physical environment = nonliving components
– Air, water, soil, and rock
• Relationships between people and environment?
– Impact of people on...
– Impact of environment on...
• Resources:
– Renewable
– Nonrenewable
The Nature of scientific inquiry
• Science - process of producing knowledge (science is measurements- how to measure things- the better you measure it, the better your explanations will be)
– Careful observation
– Explanations to make sense of observations
• Basic Assumption
– “natural world behaves in a consistent and
predictable manner that is comprehensible through
careful, systematic study”
Hypothesis:
· Data gathered, observations made… now explain
- How, why, what
· Is there only one possible explanation (hypothesis)
- Opposing hypotheses
· When does a hypothesis become an accepted part of scientific knowledge?
- From constant hypotheses: we gain a “theory” and a “law”
- Prediction made based on hypothesis tested and found to follow prediction
- Multiple verifications needed
Theory:
· Hyposthesis survives extensive scrutiny and competing ones have been eliminated
· Well-tested and widely accepted view
· - “that’s only a theory”
CONT.
CHAPTER 1:
Matter and Minerals presents the fundamental characteristics of earth materials. The chapter
begins with minerals and how they are defined, then delves deeper to review the building blocks of
minerals: atoms and atomic particles. From there, the main types of ionic bonding are presented.
The final section in the chapter steps back to look at mineral properties, how minerals are
identified, and the main mineral groups
Minerals: Building blocks of rocks
· Mineralogy
· Important part of human history
- Flint and chert
- Gold, silver, copper
- Bronze
· Naturally occurring inorganic solid with an orderly crystalline structure and definite chemical composition (identity)
- Inorganic; three things not present: has none of the below elements (C,H,)- but SiO2 is present- H2O would be considered inorganic, even though it has hydrogen and oxygen, but is inorganic because of the nonexistent presence of carbon.
- Organic; has three different elements: Carbon, Hydrogen, Oxygen (C,H,O)- ex. CO2
- Made in lab or by human intervention, = not minerals
· Generally inorganic
· Solid substance
- Ice = mineral
· Orderly crystalline structure
- Repertitve manner
- Crystals
i. Volcanic glass, obsidian
Definite chemical composition that allows for some variation
· Most minerals are compounds
- Chemical formula, SiO2 = quartz
· Composition may vary slightly if certain elements substitute for others
- Same size as to not affect crystalline structure
What is a Rock?
· Naturally occurring solid mass of mineral, or mineral0like matter
· Most aggregates of several minerals
- Individual properties of minerals retained
- Some rocks only one mineral
o Limestone is impure mass of mineral calcite
- Some rocks are non-mineral matter
o Obsidian, pumice
· Building blocks of all matter
· Smallest particle that cannot be split and retain function
o Three different parts to an atom:
1. Proton: 1 amu; +1, nucleus
2. Neutron: 1 amu, 0, nucleus
3. Electron: 1/2000 amu, -1, cloud outside (nucleus)
- All atoms (excluding H and He) formed inside massive stars by nuclear fusion.
ATOMS: BUILDING BLOCKS OF MINERALS
a. Properties of protons, neutrons, and electrons
- Protons and neutrons are very dense particles with _- masses
- Electrons have a ___ mass, about 1/2000 that of a proton
- Protons have an electrical charge of +1, and electrons have a charge of -1
- Atomic structure: nucleus, principal shells and valence shells
- “ Atomic number- electron shells, valence electrons, go naturally occurring, similar properties line up in columns.”
b. Elements: defines by their number of protons
- Atomic number is the number of _ in the nucleus of an atom
- Periodic table: organization of _
- Chemical compound: the chemical combination of __ elements
Elements vs. Minerals:
· Most minerals are chemical compounds
o Two or more elements/atoms
· Few are made up of single elements
o Native minerals
Interactions between Atoms:
· Octet rule
o 8 valence electrons, stable and “full” shell
- Noble gases
o Elements will gain or lose electrons to have a full shell
Chemical Bonds:
· Movement of electrons that result in a full valence shell
o Ionic bonds: transferred completely
o Covalent bonds: shared between
o Metallic bonds: move around, elastic
Electrons Transferred:
· Compounds have different properties than bonded elements that makes them up.
o Sodium
- Soft, silver, toxic metal that reacts explosively when exposed to water
o Chlorine
- Poisonous green gas used as a chemical weapon during WWII.
o Sodium chloride
§ Table salt
Metallic Bonds:
· Valence electrons are free to move around
o Not tethered to one atom
o All atoms share valence electrons
· Movement results in
o High electrical conductivity
o Malleability
o Other unique properties of metals.
PROPERTIES OF MINERALS :
· Have a definite crystalline structure and chemical composition
o Gives a unique physical and chemical properities
· Diagnostic properties
·
a. Optical properties :
Luster= shiny metal surface
Submetallic luster= slightly dull
Nonmetallic luster = Lighter streak
i. Luster: the appearance or quality of light reflected from the surface of a mineral
ii. Color
iii. Ability to ___ light: opaque or transparent …
o Most conspicuous: only a diagnostic for a few minerals.
o Slight impurities in chemical composition of mineral can change color dramatically
o Ruby vs. sapphire AI2O3= Corundum
o Streak:
- Color of mineral in powdwered form
- Rub sample on unglazed porcelain tile (leaves black streak- gold leaves a yellow streak.)
- Metallic minerals: dark dense nonmetallic minerals produce a streak
o Opaque, translucent, transparent
o Crystal shape or habit
o Characteristic shapw of indidual mineral crystals or aggregates of crystals
· Mineral strength: hardness
o Chemical bonds holding it together
- Strength determines how minerals break or deform under stress
· Hardness: resistance to abrasion or scratching
o Moh’s scale : 1-10
· Mineral strength: cleavage
o Tendency of mineral to break along planes of weak bonding
o Produces smooth, flat surfaces where mineral is broken
o Not all minerals will cleave
o Cleavage can be easily confused with crystal shape
Mineral strength: fracture
· Property resulting from chemical bonds that are approx.. equal in strength
o Irregular: uneven broken surface
o Conchoidal: smooth curved surface
o Splintery fibrous (look at slide 42)
Mineral strength: tenacity
· Mineral’s resistance to breaking, bending, cutting, or deforming
o Ionic bonds brittle, tend to shatter
o Native metals are malleable, hammered, without breaking
o Sectile minerals can be cut into thing shavings
o Elastic minerals will return to original shape after bent
· Types of minerals:
o Brittle
o Flexible
o Malleable
o Sectile
o Elastic
Density & Specific Gravity
· Specific gravity describes density of mineral
o Ratio of mineral’s weight of equal volume of water
· Most have specific gravity between 2-3
o Metallic minerals much higher (20 for gold)
· Can be estimated by hefting a mineral in your hand.
Fun Specific Mineral Properties
· Taste (halite is salty)
· Feel ( talc is soapy; graphite is greasy)
· Smell (sulfur smells like rotten eggs)
· Magnetism (some drawn to magnet, others can pick up iron objects)
· Optical properties (calcite refracts light)
· Effervescence (carbonate minerals fix when exposed to dilute acid)
MINERAL GROUPS: (silde 50)
· Over 4,000 named minerals, but only a few dozen are abundant in Earth’s crust
o Rock-forming minerals
§ Majority made from 8 elements
· Economic minerals
o Less common
o Used extensively in manufacture of products
· Silicates
o Most common (more than 800)
o 90% Earth’s crust
· Nonsilicates
o Far less abundant
o Some very important economic minerals
SILICATE MINERALS:
· Silicon-oxygen tetrahedron
o Four ) covalently bond to much smaller Si
o Tetrahedra can be joined into chains, sheets, or 3D networks by sharing O atoms.
· Formed in all places
o Molten rock cooling
o Form at earth’s surface and weathered
o Form at extreme pressures during mountain building
· Light vs. Dark
o Based on chemical makeup
· Lights: feldspars, quartz, muscovite, clay minerals
o Contain varying amounts of AI, K, Ca and Na
· Dark: Pyroxenes, Amphibole, Olivine, Biotite, Garnet
o Dark color and high specific gravity from iron content
FELDSPARS: MOST ABUNDANT
- Found in all three types of rocks
- Two directions of cleavage at 90*
- 6 on a Moh scale
QUARTZ:
- Common to all three types of rocks
- Impurities cause a variety of colors
- 7 on a Moh’s scale
- Forms hexagonal crystals with pyramid-shaped ends
- Exhibits conchoidal fracture when broken
MUSCOVITE: MICA FAMILY
- Excellent cleavage in one direction
- 2.5 on Moh’s scale
DARK SILICATE MINERALS:
· Olivine is a major constitutent of dark igneous rocks
o Abundant in Earth’s upper mantle
· Pyroxenes important component of dark-colored igneous rocks
o Augite is black, opaque, with two directions of cleavage at 90*
· Amphibole group includes minerals that commonly make up the dark portion of light-colored rocks
o Hornblende is a dark black mineral with two cleavage planes at 60* and 120*
· Biotite is dark, iron-rich member of mica family
o Excellent cleavage in one direction
§ Very similar to muscovite
· Garnet
o Glassy luster, no cleavage, conchoidal fracture
o Color varies, commonly deep red
o Well-developed crystals have 12 diamond-shaped faces
o Most commonly found in metamorphic rocks
NONSILICATE MINERALS:
· Divided into groups based on anion (negatively charged ion) common to the group
· Make up only about 8% of Earth’s crust
o Some other occur in significant amounts in sedimentary rocks
o Some are economically important
· Carbonates contain carbonate ion, Co3>-2
o Calcite and dolomite: used as road aggregate, building stone, and cement
o Halite )halide) table salt
o Gypsum (sulfate) used in plaster
o Oxides are important iron ores
o Other economically important ones
§ Sulfides (galena, sphalerite)
§ Native (gold, silver, copper)
§ Fluorite
§ Corundum (ruby, sapphire)
§ Uraninite
ROCKS (CHAPTER 2)
EARTH AS A SYSTEM:
· Interactions between components of earth system
o Origin of igneous, sedimentary, and metamorphic rocks
o How are they connected?
§ Any rock can be transformed into any other rock type under the right conditions.
THE BASIC CYCLE:
· Rocks are not stable unchanging mases over geologic time scales
o Cycle happens over million or billions of years
· Different stages of the rick cycle are occurring today over Earth’s surface
· Alternative paths
o Not direct igneous -> sedimentary -> metamorphic
· Cycle driven by Earth’s internal heat and external processes
o Weathering and erosion
IGNEOUS ROCKS
· Form when magma or lava cools and crystalizes
o Magma generated most commonly by melting in the mantle; some by the crust
o Rises because it is less dense than surrounding rock
o Reaches surface: lava
· Extrusive or volcanic eruption not violent
· Abundant in NW and many oceanic islands (Hawaii)
· Intrusive or plutonic rocks
o Most magma never reaches the surface
o Only exposed at surface by uplift and erosion
§ Mount Rushmore and the Black Hills (South Dakota)
§ Yosemite National Park (California)
CRYSTSLIZATION:
· Magma contains ions including silicon and oxygen, gas (water vapor) confined by pressure, and some solid crystals
· Crystallization occurs as mobile ions arrange into orderly patterns during cooling
o As cooling continues, more ions are added to the crystals until all of the liquid becomes a solid mass of interlocking crystals
· Rate of cooling strongly influences crystal sixe
o Slow cooling results in fewer. Larger crystals
o Quick cooling results in a large number of ingrown crystals
o Instantaneous cooling ( “quenching” ) results in randomly distributed atoms, no crystal growth, and formation of volcanic glass.
· Crystallization is also influenced by magma composition and dissolved gas.
IGNEOUS COMPOSITIONS
· Igneous rocks are mainly composed of silicate minerals
o Silicon and oxygen + =Al, Ca, n=NA, K, Mg, and Fe make up 98% of most magmas
o Also includes small amounts of trace elements
§ Titanium, manganese, gold, silver, urnanium, etc.
· Dark silicates are rich in iron and/or magnesium and relatively low in silica
o Olivine, proxene, amphibole, biotite mica
· Light silicates contain greater amounts of potassium, sodium and calcium and are richer in silica.
o Quartz, muscovite mica, feldspars
o Feldspars are most abundand mineral group
§ 40% of most igneous rocks
· Igneous rocks can be divided into broad according ro proportions of light and dark minerals
· Granitic (felsic) rocks
o Granitic composition: made up of almost entirely light-colored silicates
§ Quartz and potassioun feldspar + silica
o Most contain ~70% silica
o Major constituent of continental crust
· Basaltic (mafic) rocks
o Contain at least 45% dark silicate minerals and Ca-rich plagioclase but no quartz
o Mafic = magnesium + ferrum (iron)
o Darker and more dense than grantic rocks ecause of iron content
· Make up ocean floor and volcanic ocean islands
· § Andesitic (intermediate) rocks
§ falls between granitic and basaltic
composition
§ Mixture of both light- and dark-
colored minerals
§ Contain at least 25% dark-silicate
minerals
§ Amphibole and plagioclase feldspar
§ Associated with volcanic activity at
continental margins
§ Aleutian chain
·
· Ultramafic rocks
o Contain mostly dark colored minerals
§ Olivine and prozyene (ferromagnesian)
o Rare at earth’s surface
o Main consitiutent if upper mantle
TEXTURE:
“described based on the size, shape, and arrangement of mineral grains:”
· Texture can be used to make inferences about a rock’s origin
o Large crystals indicate slow cooling
o Slow cooling is common in magma chambers deep in the crust
o A rock with large crystals probably formed deep in the crust
· Porphyritic
o Different minerals crystalize under different temperature and pressure conditions
o One mineral can reach a large size before other minerals start to form’large crystals (phenocrysts) in a matrix of smaller crystals (groundmass)
· Glassy
o Develops when rocks cool rapidly
o Ions freeze in place before they can arrange themselves in an orderly crystilinne structure
· Vesicular
o Exhibits voids left by gas bubbles that remained when lava solidified
o Form in upper zone of lava flow
· Pyriclastic (fragmental)
o Composed of individual rock fragments ejected during explosive volcanic eruptions
o Particles could be very fine ash, molten blobs, or large angular blocks
· (look at slide 17)
· Granite
o Coarse-grained
o Forms when magma is solidified slowly at depth
o Uplifrted during mountain building
· Rhyolite
o Eztrusive fine-grained equivalent of granite
o Light-colored silicates, usually buff, pink, or light grey
o Frequently contained voids and fragments of volcanic glass
o Cooled rapidly at earth’s surface
· Obsidian
o Natural volcanic glass
o Dark in color ( from metalc ions), but felsic composition
· Pumice:
o Vesicular volcanic glass
o Gas escape from molten lava forms a frothy, gray rock
o Many pieces float in water because of vesicles
· Andesite
o Medium-gray extrusive igneous rock
o Fine grained or porphyritic with phenocrysts of plagioclase feldsoar or amphibole
o Major contstitutent of volcanoes along the pacific rim
§ Andes mountains
§ Cascade range
· Diorite
o Coarse-grained intrusive equivilaent of andesite
o Few or no visable quartz crystals
· Basalt
o Most common extrusive igneous rock
o Dark green to black, fine grained
o Contains proxeyne, olivine, and plagioclase feldspar
o Relatively common at earth’s surface
§ Volcanic islands (Hawaii, Iceland)
§ Upper layeres of the oceanic crust
§ Central Oregon and Washington
· Gabbro
o Coarse grained intrusive quivilent of basalt
o Not commonly exposed at earth’s surface
o Significant component of oceanic crust
HOW DO THEY FORM?
· Magma can evolve
o Different rock types can be generated from the same melt
· Bowen’s reaction series describes which solidify at specific temperatures
o First to crystalize is olivine, the pyroxene, and plagioclase
o Amphibole and biotite at intermediate temperatures
o Muscovite and potassium feldspar during late coling
o Quartz is last to solidify
· Minerals that form in the same temperature range tend to be associated in the same igneous rocks
· Magmatic differentiation is the formation of one or more secondary magmas from a single parent magma
o Explains diversity of igneous rocks
o Magma composition continually changes during cooling
o As crystals form, certain elements are selectively removed, resulting in a depleted in a depletd magma
o Crystal settling occurs when dense minerals sink to the bottom of a maga chamber
WEATHERING:
· Transformation of a rock reach equilibrium with its environment
o Natural respose of materials to a new environment
o Two basic categories: mechanical and chemical
§ Generally occur simultaneously
§ Erosion transports weathered rock
MECHANICAL
· Process of breaking down rocks into similar pieces
o Each piece retains the same physical properties of the original material
o Increases surface area available for chemical weathering
FROST WEDGING
· Ice expands ~9% when it freezes
· Traditional explanation: water fills cracks in rocks and expands
· Recent research: lenses of ice grow within cracks and pore spaces of rock until rocj is weakened and fractures
SALT CRYSTAL GROWTH
· Sea spray or salty groundwater evaporate in rock;s crevices and pore spaces
· Salt crystals grow larger and weaken the rock by pushing apart surrounfign grains or enlarging tiny cracks
· Common on rocky shorelines and in arid regions
SHEETING
“occurs when concentric slabs of intrusive igneous rock break loose
- Removal of overlaying rock reduces pressure and outer layers ecpanf and separate
- Continues weathering results in exfoliation domes
BIOLOGICAL ACTIVITY
· Plant roots grow into cracks and wedge the rock apart
· Burrowing animals expose rock to increased weathering
· Decaying organisms produce acids, which contribute to chemical weathering
· Humans
CHEMICAL
· Alters the internal structure of minerals
o Elements are removed or added
o Original rock is transformed into new stable material
o Makes outer portions of some rocks more susceptible to mechanticla weathering
· Water is most important agent of chemical weathering
o Oxygen dissolved in water causes oxidation
o Carbon diozide dissolved on water is carbonic acid
§ Feldspar minerals are broken down into clay minerals
§ Silica is carried away by ground water
o Quartz is very resistant to chemical weathering
SEDIMENTARY ROCKS
· Form after weathering breaks rocs down, gravity and erosional agents transport and deposit the sediment, and the sediment becomes llithified
o Most sedimentary rock is deposited by solid materieal settling out of a fluid
· Sedimentart rocks make up ~5% of Earth’s outer 10mi, but account for 65% of all continental rock outcrops
o Used to reconstruct details about earth’s history
o Economically important
§ Coal, petroleum, and natural gas, metals, fertilizer, construction materials.
· TWO TYPES;
o Detrital
§ Form from solid particles weathered from other rocks
· Contain a wide variety of minerals and rock fragments
o Clay and quartz are most common
· Distinguished by particle size
o Also useful for determining environment of deposition
o Higher energy carries larger particles
· Mineral composition is also used to classify detrital sedimentary rocks
o Chemical
§ Form form ions carried in solution
· Water carries ions in solution
· Solid material precipitates to form chemical sediments
o E.g. salt left behind when saltwater evaporates
· Materials precipated by organisms are known as biochemical sediments
o E.g. shells and hard parts
· Limestone is composed of calcite (CaCO3)
o Nearly 90% is formed by organisms
LITHIFICATION OF SEDIMENT
· Process by which sediment is transformed into sedimentary rock
o Ceompaction occurs when grains are pressed closer together so that pore space is reduced
§ Weight of accumulated sediment
§ Most significant in fine-grained rocks
o Crementation occurs when ewater containing dissolved minerals moves through pores
§ Cement precipitates fills pores, and joins particles together
§ Calcite, silica, and iron oxide are common cements
§ Significant in coarse-grained rocks
FEATURES OF SEDIMENTARY ROCKS
· Strata or beds
o Characteristic of sedimentary rocks
o Thickness ranges from microscopic to tens of meters
o Bedding planes ark the end of one episode of sedimentation and the beginning of another
· Fossils are traces or remains of life found in some sedimentary rocks
o Important clues of ancient environment
o Can be used to match up rocks of the same age found in different places.
METAMORPHIC ROCKS
· Produced when preexisting parent rock is transformed
o Parent rock can be igneous, sedimentary, or metamorphic
· METAMORPHISM occurs when parent rock is. Subjected to a different physical chemical element.
o Elevated temperature and pressure
o Changes mineralogy, texture, and sometimes chemical composition
o Equilibrium with new environment
· Metamorphism progresses incrementally
o Low-grade (slight changes) to high-grade (substantial changes)
· TWO SETTINGS:
o Contact metamorphism
§ Rock temperature increases because of intruding magma
o Regional metamorphism
§ Pressure and high temperature during mountain building
WHAT DRIVES METAMORPHISM?
· Agents of metamorphism
o Heat (from intrusion of magma or burial)
§ Chemical reactions and recrystallization of new minerals.
o Confining pressure (equal in all directions because of burial)
§ Compaction and recrystallization of new minerals
o Differential stress (greater in one direction because of mountain builfing)
§ Deformation and development of metamorphic textures
§ Rocks can react by breaking (brittle) or bending (ductile) depending on temperature
o Chemically active fluids (hydrothermal fluid in rich ions)
§ Catalyze recrystallization reactions
§ Can dissolve a mineral from one area and precipitate it in another
§ Can change chemical composition of surrounding rock.
METAMORPHIC TEXTURES
· Metamorphism can change the texture of a rock
o Low-grade metamorphism makes rocks and more dense
o High-grade metamorphism causes recrystallization and growth of visible crystals.
FOLIATION
· Foliation is the development of a flat arrangement of mineral grains or structural features
o Foliation is characteristic of regional metamorphism
o Friven by compressional stress
§ Causes mineral grains to develop parallel alignment
o Includes: parallel alignment of micas
§ Parallel alignment of flattened pebbles
§ Separation fo light and dark minerals
§ Development of rock cleavage
· Nonfloated (non-linear) rocks occur when deformation is minimal and parent rock is composed largely of stable minerals.
COMMON METAMORPHIC ROCKS
· Common foliated metamorphic rocks:
o Slate has characteristic rock cleavage
§ From metamorphism of shale or volcanic ash
o Phyllite has larger mineral grains than slate, which give it a glossy sheen and wavy surface
o Schist is formed by regional metamorphism of shale
o Gneiss is a banded metamorphic rock that may have intricate folds.
· Common nonfoliated metamorphic rocks:
o Marble is a coarse crystalline rock
§ From metamorphism of limestone
o Quartzite is very hard because of fused quartz grains
§ From metamorphosed quartz sandstone.
CHAPTER 3,4 (chapter 6 in the 9th Ed.) LANDSCAPES
KEY CONCEPTS:
6.7- Discuss streamflow
6.8- summarize the ways that streams erode
6.9- contrast regional floods and flash floods
6.10- discuss the importance of groundwater and describe distribution and movement
6.1-
· Mass movement refers to the downslope movement tof rock and soil under the direct influence of gravity.
Mass movement and landform development: 1
· Slump – downward sliding of a mass of a rock or unconsolidated material that
· Rockslide
· Debris flow
· Earthflow
SLOPE CHANGES THROUGH TIME
· Most rapid and spectacular mass movements occurs in area of rugged, geologically young. Mountains
· As a landscape ages, massive and rapid mass movement processes give way to smaller, less dramatic downslope movement.
Mass movement and landform development: 2
· Excavating the grand canyon.
CONTROLS AND TRIGGERS OF MASS WASTING
· Gravity is the controlling force
· Other factors overcome inertia to create downslope. Motion
o Slope material is gradually weakened
o Slope gets closer and closer to being unstable until a trigger initiates downslope movement
§ Saturation with water
§ Oversteepening
§ Removal of vegetation
§ Earthquakes.
· Saturation
o Water in pore space reduces cohesion and allows particles to slide
o Water adds weight to sediment
· Oversteepening
o Unconsolidated sediment forms a stable slope at a certain angle of response depending on the size and shape of the particles.
o Stream of undercutting a valley
o Waves undercutting a cliff
o Human activity
Oversteepened slopes
· Angle of response
Controls and triggers of mass wasting (2)
· Removal of vegetation root systems that bring sediment
o Forrest fires, deforestation, development farming
· Earthquakes can dislodge rock and unconsolidated material
· Many mass wasting events occur without an identifiable trigger.
THE HYDROLIC CYCLE:
· Water moves between the ocean, atmosphere, and land vis the hydrolic cycle
· Hydrosphere is all of the reservoirs where water is held
o J
o J???
o J
o J
· 95% of hydrosphere is the global ocean
· 1.76% is ice sheets and glaciers
· 2% is lakes, streams, groundwater, and atmosphere
· Hydroligic cycle is powered by the Sun.
· Water enters atmosphere from the oceans via evaporation
· Winds transport water through the atmosphere
· Precipitation either falls to the ocean or continents
o Precipitation to the oceans completes the hydrolic cycle
o Precipitation to the continents must return to the ocean.
· Some water soaks into the ground (infiltration)
· Surplus water flows over the surface (runoff)
· Water absorbed by plants is eventually released via transpiration
· Evapotranspiration is the combined effects of evaporation and transpiration
· Precipitation I old regions becomes part of glaciers
o Significant reservoirs: melting all glaciers would cause a sea level rise dozen of meters.
· Hydrologic cycle is balanced
o Average annual precipitation equals amount of water entering the atmosphere from evaporation
· Precipitation that forms runoff depends on:
o Intensity and duration of rainfall
o Amount of water already in the soil
o Nature of the surface material
o Slope of the land
o Extent and type of vegetation
RUNNING WATER:
· Runoff starts as unconfined thin sheets across hillslopes
· Flow develops threads of current in tiny channels called rills
· Rills converge to form gullies
· Gullies converge to form streams and rivers that carry water from broad areas.
6.7- drainage basin and divide.
· Divide determines which way the rills run.
Drainage basins
· Drainage basins (separated by divides) are the land area that contributes water to a river system
· Divides vary in scale
6.8 – Mississippi river drainage basin
RIVER SYSTEMS:
· A river system carries water from an entire drainage basin
o Includes three zones:
§ Sediment production (erosion dominant)
· Where most water and sediment is derived
· Headwater regions
§ Sediment transport
· Transportation through
§ ???
Streamflow Characteristics
· Water flow in slow-moving streams van be laminar
o Moves in roughly straight-line paths parallel to stream channel
· Most streamflow is turbulent
o Water moves erratically in swirling motion
o Lifts
· ?
Factors affecting Flow velocity:
· Flow velocity varies along a stream and through time
· Flow velocity depends on:
o Channel slope or gradient
o Channel size and cross-sectional shape
o Channel roughness
o Amount of
· Gradient is the vertical drop over a specified distance
o Varies from stream to stream and over a single stream’s length
o A steeper gradient provides more energy for flow.
· Shape, size, and roughness for channel affect the amount of friction between channel and water
o Higher friction creates turbulence and slower water
· Discharge is the volume of waer flowing past a certain point in a given unit of time (m3/s)
o Intermittent streams only flow during wet periods
o Ephemeral streams carry water after heavy rainfall
Changes from upstream to downstream
· The cross-sectional view of a stream from headwaters to mouth is called longitudinal ___??
o ??
o ??
[slide 20] . . .
THE WORK OF RUNNING WATER
· Raindrops knock sediment particles loose
· Flow of water in a stream can dislodge and lift particles from the channel
o Erodes poorly consolidated material quickly
o Can undercut banks
· [ONCE IN THE STREAM] Hydraulic force can also cut bedrock
o Enhanced by particles carried in water
o Swirling pebbles can charge potholes in channel floors
Three ways to transport sediment:
· Dissolved load
o Delivered by groundwater
o Not effected by velocity
· Suspended load
o Clay and silt particles
o Largest component of load
· Bed load
o Sand, gravel, large boulders
o Only in motion intermittently
· Capacity is the maximum load of solid particles a stream can transport per unit of time.
o Increases with discharge
· Competence is a stream’s ability to transport particles based on size
o Increases with flow velocity
· As flow decreases competence is reduced
o Particles settle when flow reaches critical settling velocity for that particle size
o Sorting separates particles Of various sizes
· Alluvium is material deposited by a stream
STREAM CHANNELS
Bedrock:
· Cut into rock
o Common in headwaters with steep gradient
o Transport coarse particles
o Rapids and waterfalls common
o Channel pattern is controlled by underlying geologic structure
§ Often winding and irregular
Alluvial
· Composed of loosely consolidated sediment
o Continually being eroded, transpored, and redeposited
· Shape is controlled by average sediment size, and discharge
· Two common types:
o Meandering channels
o Braided channels
MEANDERING CHANNELS
· Have sweeping bends called meanders
o High suspended load
o Deep, smooth channels
· Banks are [fairly] resistant to erosion
o Most erosion occurs in the outside of the meander, or cut bank, where velocity is the highest
o Sediment is deposited along the inside of the meander where turbulence and velocity are low, forming point bars
· Meanders migrate laterally and downstream
o May form a cutoff and oxbow lake through narrow neck of land
BRAIDED CHANNELS
· A complex network of converging and diverging channels
o Form where most of stream load is coarse (sand and gravel) and discharge is variable
o Wide and shallow (bank material erodes easily)
o Common at the end of glaciers
SHAPING STREAM VALLEYS
· A stream valley is the channel and surrounding terrain that contributes water to the stream
o Divided into two general types:
§ Narrow, V-shaped valleys [think of creeks/creekbeds]
§ Wide valleys with flat floors
BASE LEVEL AND STREAM EROSION [how much material is transported]
· Base level is the lower limit to how deep a stream can erode
o Velocity and ability to erode are greatly reduced
· Change in base level causes readjustment of stream
VALLEY DEPPENING
· Downcutting
o Dominant when gradient is steep and channel is above base-level
o Abrasion and hydraulic power
o Produces V-shaped valley with steep sides
§ Rapids and waterfalls common
· Downward erosion becomes less dominant as channel reaches base level
o Channel becomes meandering
o Lateral erosion creates a broad, flat valley floor called a floodplain
· Incised meanders flow in steep, narrow valleys
o Meanders develop when streams is near nase level, but base level falls and stream starts downcutting again
§ Sea level fall
§ Uplift
· Stream terraces are the remnants of former floodplains
o Form after river adjusts to relative drop in base level then floods again
o Floodplain is produced at a level below the old one.
DEPOSITIONAL LANDFORMS
· Streams transport sediment and deposit it downstream
o Bars are deposits of sand and gravel
§ Temporary: material will eventually be carried to the ocean
o Longer life span depositional features:
§ Deltas
§ Natural levees
DELTAS
· Flow decreases and sediment falls
· Delta grows outward and gradient lessens
[as the stream extends its channel, the gradient is reduced. During flood stage come of the flow is diverted to a shorter, higher-gradient route forming a new distributary. ]
· Channel chokes with sediment, divides, and moves to higher-gradient areas
· Distributaries carry water and sediment away from main channel
NATURAL LEVEES
· Built by successive floods on rivers in broad floodplains
o Flow decreases when streams overflow
o Coarse sediment deposited in thin strips parallel to channels
o Fine sediment distributed across floodplain
· Built by successive floods on rivers in broad floodplains
o Flow decrease when streams overflow
o Coarse sediment deposited in thin strips parallel to channels
o Fine sediment deistributed across floodplaun
o Back swamps form because drainage is poor behind levees
§ Yazoo tributaries parallel the rier until they can breach the levee
FLOODS
· Occur when stream discharge exeeds channel capacity
o Among most common and most destructive natural hazards
· Most floods occur because of weather
o Snowment, heavy rains over large regions
o Flash floods
§ Limited geographic extent
§ Influenced by rainfall intensity, surface conditions, topography
§ Common in urban areas (rapid runoff)
o Failure of dams or artificial levees
· Controlled by: [slide 44]
o Artificial levees
§ Earthen mounds increase volume of water the channel can hold
o Flood control dams
§ Store water and let it out slowly
o Channelization
§ Artificial cutoffs shorten the stream and increase gradient and velocity
· Nonstructural approaches may be more efficient
o Less expensive
o Sound floodplain management
§ Identifying high-risk areas, appropriate zoning regulation implemented to minimize development, promote more appropriate land use
PREPARING FOR THE EXAM
“the best way you can”
- Multiple choice,
- Short answer at the end (1-2 sentences)
- More information on Thursday
- More notes will be posted on canvas
Groundwater
Exists in tiny pore spaces between grains of soil and sediment plus narrow joints and fractures in bedrock
Largest reservoir of freshwater readily available to humans
· Source of 40% water
· Drinking water for -44% of population
· 40% of irrigation water
· 25% of water used in industry
Overuse can cause streamflow depletion, land subsidence, and increased pumping cost
Role
· Important erosion agent
o Forms sink holes
o Stabilizes streamflow
Distribution
· Comes from infiltration of rainfall into the ground
o Amount is influence by slope, surface material, intensity of rainfall, vegetation
· Potable= undrinkable
· Belt of soil moisture
o Film of water of soil particles near the surface
· Zone of saturation
o All pore space is filled w/ water: groundwater
o Upper limit is water table
· Area above the water table is called the unsaturated zone
· Water table is irregular
o Subdued replica of the surface
§ Highest below hills
o Contributing factors
§ Groundwater moves slowly
§ Water “piles up” between stream valleys
§ Variations in rainfall
§ Changes in permeability of sediment
· Water table falls during droughts
Factors influencing Groundwater
· Porosity
o % of total volume of rock or sediment that consists of open pore space
o spaces between particles, joints, faults, dissolution cavities, vesicles
o quantity of groundwater depends on porosity
· percolation= water passes over the rocks and makes it’s way through
· permeability
o a material’s ability to transmit fluid
o if spaces are too small, water cannot move through
o aquitards
§ impermeable clay layers that prevent water movement
o aquifers
§ rock or sediment that water moves through easily
o aquiclude
§ water will NOT pass through
Movement of groundwater
· moves slowly from pore to pore
o pressure increases w/ depth in zone of saturation
· spring – natural flow of groundwater
o where water table intersects w/ surface
o aquitard prevents downward movement
· perched water table – localized zone of saturation above aquitard
Springs
Many different sources
Well
· hole drilled into saturation zone to remove groundwater
· cone of depression is created from a lowering of the water table (drawdown) directly do to water removal
· artesian system - free-flowing groundwater from an outlet far above water table
· confined water table – aquifer
o aquitards above and below
Environmental Concerns
Overuse threatens supply
Excessive withdraw causes land to sink
Contamination
· septic tanks, sewer systems, farm wastes
· purification can happen by natural processes
· pollution can be identified – treated or abandoned
Geologic Work of Groundwater
Most groundwater contains carbonic acid
· CO2 from air and decaying organic matter
· Dissolves limestone
· Forms caverns, sinkholes, and karst landscapes
Caverns form due to the erosional work of groundwater
· Created in the zone of saturation
· Dissolved load is discharged into streams
· Decorated by calcium carbonate deposits
o Form when cavern is above water table
o Stalactites hang from ceiling
o Stalagmites develop upward from the floor
Karst Topography
Results from dissolution of groundwater
Geological Work of Groundwater
High content of groundwater contains
GLACIERS: Ch. 7
CHAPTER OUTLINE
7.1 GLACIERS AND THE EARTH SYSTEM
a. _______________: A Part of Two Basic Cycles
b. Valley (Alpine) Glaciers
c. Ice Sheets
i. __________________ sheets
ii. ________________ and _____________ still have ice sheets
iii. Ice shelves
d. Other Types of Glaciers
7.2 HOW GLACIERS MOVE
a. Observing and Measuring Movement
b. Budget of a Glacier: _______________ Versus _________________
i. Glacial zones
ii. Glacial budget
iii. Glaciers in retreat: Unbalanced glacial budgets
7.3 GLACIAL EROSION
a. How Glaciers Erode
b. Landforms Created by Glacial Erosion
i. Glaciated _____________
ii. ___________________
iii. ___________ and ______________
iv. ______________
7.4 GLACIAL DEPOSITS
a. Types of Glacial Drift
i. __________________
ii. __________________
b. Moraines, Outwash Plains, and Kettles
i. Lateral and medial moraines
ii. End moraines and ground moraines
iii. Outwash plains and valley trains
iv. Kettles
c. Drumlins, Eskers, and Kames
i. Drumlins
ii. Eskers and kames
7.5 OTHER EFFECTS OF ICE AGE GLACIERS
a. _______________________
b. __________________________
c. Ice Dams Create ____________________
d. ______________ Lakes
7.6 EXTENT OF ICE AGE GLACIATION
7.7 DESERTS
a. Distribution and Causes of Dry Lands
b. Geologic Processes in Arid Climates
i. Dry-region weathering
ii. The role of water
7.8 ARID LANDSCAPES OF THE AMERICAN WEST
a. __________ and __________
b. ______________ Plateau
7.9 THE WORK OF WIND
a. Wind Erosion
i. _____________ and ___________
ii. Armoring the desert surface
iii. ___________ _________________
b. Wind Deposits
i. _____________________
ii. _________ ___________
7.5
· Forced __
Other effects of Ice Age Glaciers
· Many present-day stream courses bear little resemblance ____
· Rebounding of land
· Ice sheets dam meltwater and create lakes
o Proglacial lakes
· World-wide change in sea level
o Up to 100m lower during the ice age
· Pluvial lakes formed during cooler, wetter climates
7.6 EXTENT OF ICE AGE GLACIATION
· Last ice age began between 2 and 3 million yrs ago during the quaternary period.
· Ice sheets and alpine glaciers were far more extensive than they are today
o Almost 30% of earth’s land was glacially influenced.
· 30% of Earth’s land surface is arid
· Affected by many geologic processes
o Mountain building, running water, wind
· Dry climate
o Yearly precipitation less than the potential loss of water by evaporation
o Desert (arid)
o Steppe (semiarid)
§ Marginal and more humid variant of desert
§ Transition zone that surrounds the desert
o Concentrated in subtropics and middle latitudes.
DISTRIBUTION CAUSES OF DRY LANDS
· African, Arabian, and Australian deserts are a result of prevailing winds
o Subtropical highs in the lower latitudes
o Subsiding air is compressed and warmed
§ Created clear skies and ongoing dryness
· Middle
o ??/
THE ROLE OF WATER
· Ephemeral streams only carry water during specific rainfall events
o Little vegetation to mediate runoff
o Flash floods are common
o Responsible for most erosion in deserts
§ Wind primarily transports sediment.
ARID LANDSCAPES OF THE AMERICAN WEST
· Regions with drainage have ephemeral streams that do not flow out of the basin in to the ocean
o For example. Basin and range region in western U.S.
§ Characterized by ____
§ _______
· Occasional heavy rain rivers with sediment
· Alluvial fans deposited at mouth of a canyon
· A bajada is created when several alluvial fans from adjacent canyons merge
· A playa lake forms when rainfall is sufficient to cover the basin floor.
o Salt flats can form when water evaporates
· Continues erosion gradually diminishes local relief
o ___
· Colorado plateu is centered on the four corners area where Utah, Arizona, new Mexico, and Colorado meet
· ??
· Often cliff-forming strata are jointed and break along successive jpints and retreat back into the land maintaining reprendicular faces
o Mesas are flat-topped hills where the cliff retreats along the margins of a plateu
o Buttes are related to a mesa
o ???
7.9 THE WORK OF THE WIND
· Just like a river, wind transports fine particles in suspension, while heavier particles travel along the bed load
· Deflation
o Lifting and removal of loose material
o Clay and silt only
· Saltatio
o Rolling or skipping of larger particles along the surface
· Blowouts
o ??
Working against the wind = plants
· Wind can also ereode via abrasion
o Occurs in dry regions and along some beaches
o Windblown sand polishes exposed rock surfaces
o Generally <1m above the surface
· Generally two distinctive types:
o Extensive blankets of silt from suspended load called loess
o Mounds and ridges of sand from bed load called dunes.
WIND DEPOSITS
· Loess is windblown silt
o Tends to erode in vertical cliffs
o Lacks bedding
· Deserts and glacial deposits of stratified drift are primary sources of silt
· Sand accumulates in mounds and ridges where the path of wind is obstructed
· Many dines have asymmetrical profiles
o Leeward (sheltered) slope is steep and windward slope is gently inclined
§ Sand accumulated in the slip face (leeward side) because wind velocity is reduced just beyond the crest of the dune
§ Dunes migrate slowly in windward
