-site at surface above focus where energy is released
Types of faults
Normal fault: -when two plates extend (go away from each other) -hanging wall down -foot wall stays in place
Reverse Fault: -due to compression (2 plates come together) -hanging wall goes up
Thrust fault: -due to compression -a type of reverse fault where the angle of displacement is less steep than a normal reverse fault
Strike- slip fault: -due to regional shear -no vertical displacement (like the other 3) -the plates slide side by side
-surface expression of vertical movement on a fault (when the hanging wall moves down, you can see some of the side of the foot wall- this is the fault scarp) -end up seeing a depression after it gets eroded
Faulting and ages of rocks
-faulting causes rocks of diff. ages to become juxtaposed (next to one another)
-produced by seismicity (earthquakes)
-type of seismic wave -move through earth's interior -can be compressional or shear waves
Primary (p) waves: -compressional body waves -push-pull (compress/expand) motion -waves are equally spaced -travel through solids, liquids, and gases -fastest
Secondary (S) waves: -shear body waves -shaking motion -travel only through solids, not liquids -slower
-move along earth's surface -can be compressional or shear waves
Love waves: -s waves intersecting the surface -move back and forth like a writhing snake
Rayleigh waves: -p waves intersecting the surface -move like ripples on a pond
*these waves are the slowest and most destructive, but not as intense as the other waves
-device to measure ground motion -the pen that draws on a seismometer shows the intensity of the earthquake -the ground and the frame sink & rise when the earthquake occurs- this motion makes the lines that the pen draws -weight and pen stay in place -frame & paper move
Determining the epicenter
-have 3 stations recording earthquake waves -distance btw. p & s waves gets larger w/ each successive station (1,2,3) -the epicenter is where the 3 circles (stations) intersect at one point
Low vs. high magnitude earthquakes
-small mag. earthquakes usually occur @ mid-oceanic ridges or subduction zones (may not even know they happen) -higher-magnitude ones are less frequent
Order that seismic waves arrive in
-Pwaves are the fastest and get there first -S waves come next -surface waves come last
Measuring earthquake size (diff. scales)
-Mercalli intensity: scale of I to XIII, based on damage caused, subjective
-Richter magnitude: based on size of largest wave measured 100 km away -open ended scale -change of 1 unit = 10x change in energy
Other scales: "seismic moment magnitude", more accurate for distant earthquakes
Seismic waves and their speeds through different materials
-Travel faster through denser rock (peridotite- upper mantle), and slower through less dense rock (santstone- upper crust)
-Travel faster through solids (peridotite-lower mantle), and slower through liquids (molten iron alloy-outer core)
Waves moving into new material
-they bend as they move into different material -light travels faster through air and slower through water -light beams are reflected off of water and into the air and refracted under water
Structure within mantle is defined by...
-changes in velocity of seismic waves
What is the depth of the outer core determined by?
-P-wave "shadow zone" (an area in which the wave is not detected)
Liquid state of outer core is determined by...
-S-wave "shadow zone" (an area in which the wave is not detected b/c it can not go through liquids)
Where do earthquakes occur?
-along plate boundaries -not in the interior (along the coast) -Pacific
-ground shaking -landslides and avalanches -sediment liquification -fires -tsunamis
What is metamorphism?
-change in rocks due to changes in temps. and pressure while in the solid state
-the original rock that undergoes metamorphism and becomes a new rock
Rocks surrounding metamorphic rock underground are called...
less depth, temp., and pressure
-inc. pressure and temp.
-inc. pressure but not temp.
High pressure and temp. makes what kind of rocks?
-shinier rocks with bigger grains b/c they have gone through more metamorphism
-very close to surface and did not go through a lot of metamorphism
When does sandstone have a diff. name?
-it is called quartzite when it has gone through metamorphism and has a distinct crystal structure
At which temps. does metamorphism occur?
-doesn't occur below 150 degrees -occurs from 150 - greater than 1,000 degrees -below 150 deg., oil is formed and the rocks are in diagenesis
Factors controlling metamorphism
1. Chemical composition of pre-existing rock (protolith) - ex: shale, basalt, etc. 2. Change in temperature: caused by burial or proximity to intrusions 3. Change in pressure -due to burial and tectonic forces (plates going together) 4. Presence/absence of fluids: -inc. susceptibility to metamorphism 5.Time -variable; reflected in grain size -older rocks have a diff. composition than younger rocks 6. Stress regime: -compressional- nonfoliated -directional- foliated
Low-grade: temp= 100 C -500 C -pressure is relatively low
High-grade: temp= > 500 C -pressure is high
-due to contact w/ magma or lava -heat +/- fluids -little mechanical disruption
-An entire region goes through the same metamorphism (can be certain sections of the world- over several countries) -similar kinds of minerals will be in these areas -due to large scale forces + burial -generally high temp and high pressure -accompanying deformation (folding)
Similar minerals exist in areas that...
-have gone through the same amnt./kind of metamorphism
East coast vs. interior U.S. metamorphism
-east coast has higher grade metamorphic rock (ex: gneiss) than the interior
-very old rocks and the basics of plate tectonics -folded mtn. belts are the next oldest and younger rocks are the youngest
Metamorphic process determines...
-what type of met. rock you will have/ composition of it
-rock and mineral fragments -shells/fossils -mineral precipitates
*cemented into rocks
Clastic vs. chemical sed. rocks
-clastic: formed by grains -chemical: non-grain
Phys. vs. chem. weathering
Phys: mechanical breakage and disintegration (doesnt change composition of the rock- make it new, just breaks it into pieces- detritus) -Detritus: -coarse grained: boulders cobbles and pebbles -med. grained: sand-sized -fine grained: silt and clay (mud) Chem: decomposition by reaction with water
Weathering processes occur with...
-at earth's surface -low temps and pressure
Fossils can be..
-Coarse, intermediate, or fine grained
Types of physical weathering
-jointing -frost wedging (a crack occurs in the rock and ice/snow gets into it and causes it to expand) -root wedging -salt wedging -thermal expansion -animal activity
Facts about physically weathered rocks
-phys. weathered rock fragments move by gravity (flow down a hill) -large blocks often accumulate as talus below a cliff -smaller fragments are carried away by water and wind
-reaction with water disintegrates many minerals -water is the universal solvent -maximized under warm and wet conditions -tropical weathering is intensive -turns rock into heavily decomposed saprolite -chem. weathering is virtually absent in deserts -forms stable minerals from unstable precursors
-probably weathered -iron probably got into it (rust)
-soil forming processes require long periods of time -soil may be easily destroyed by human activities -soil is a crucial natural resource in need of protection -soil is only the very top of earth's crust (1st few meters)
The soil profile
-soil forms a vertical sequence of layers called a profile -profiles develop from the surface downward -individual layers are horizons
The upper horizons form topsoil, the fertile part of the soil -easily removed by erosion -1000s of years in the making
Soil forming processes-direct analogue
-can be wind, water, rivers, etc. -after soil is eroded (removed), it can take years to get it back
Zone of leaching
-upper soil profile -rain (water) and nutrients are added to the soil -ions from chemical weathering -fine silts and clays infiltrate
Zone of accumulation
-lower soil profile -ions form new minerals -silts and clays clog pore spaces
*distinct horizons reflect soil forming processes -O horizon: dark organic matter-rich surface layer A horizon: organic and mineral matter E horizon: transitional layer leached by organic acids B horizon: organic-poor mineral rich layer C horizon: slightly altered bedrock
A is topsoil E is transition B is subsoil
O, A, E are zone of leaching B is zone of accumulation
Soil genesis (formation) is influenced by which factors?
-climate: amnt. of water/warmth -substrate composition: soil parent minerals -slope steepness: soils develop best on low slopes -drainage: wet soils are more organic-rich -time: older soils are more developed -vegetation: controls type of organic matter added
4 classes of sedimentary rocks
Clastic: made from weathered rock fragments (clasts) -just grains; no chemical change in mineral composition
Biochemical: cemented shells of organisms
Organic: the carbon-rich remains of plants
Chemical: minerals that crystallize directly from water
Clastic sedimentary rocks reflect several processes...
-Weathering: generation of detritus via rock disintegration -Erosion: removal of sediment grains from rock -Transportation: dispersal by wind, water, and ice (solid particles and ions are transportated in ground and surface water) -Deposition: accumulation after transport stops -Lithification: transformation into solid rock (everything binds together)- could be done using clay, covering them in chemicals, etc
Transforms loose sediment into solid rock -Burial: more sediment is added onto a previous layer -Compaction: overburden weight reduces pore space -Cement: minerals from groundwater "glue" sediments
Classification of clastic sedimentary rocks
Classified on the basis of texture and composition -clast (grain) size: -clast composition (could be composed of specific minerals or of a mixture of igneous, sed., etc. rocks) -angularity and sphericity -sorting -character of cement
*these variables produce a diversity of clastic rocks
Clast (grain size) of clastic sedimentary rocks
-the avg. diameter of clasts Range from very coarse to very fine: -boulder, cobble, pebble, and pea gravel -coarse, med., and fine sand -coarse, med., and fine silt -coarse and fine clay
With inc. transport (farther from the source), how does grain size change?
-avg. grain size decreases as the grains get further from the source
- a sedimentary rock that is a mixture of diff. sizes and shapes of grains -more of them are rounded
-a mixture of lots of diff. grains but the majority of them are angular
-layers like pages of a book -medium-grained sand
-formed by very fine-grained material
Clast composition of clastic sed. rocks
-mineral makeup of clasts -may be individual minerals or rock fragments Mineral identity important: -stable end-products of weathering (quartz, fe-oxides, clays)= can cut them again and again and you will still have the same rock -unstable minerals signify special conditions (feldspars)= when you keep breaking the rock, it will become a new kind of rock
Angularity and sphericity of clastic sed. rocks
-indicate degree of transport -fresh detritus is usually angular -grain roundedness and sphericity inc. with transport
Maturity: a measure of the degree of processing -textural maturity: degree of roundness and sorting -mineral maturity: degree of unstable mineral removed *maturity helps to reconstruct depositional conditions
-rocks that came from the top to the bottom of the mtn. and have deposited -when the rocks go through the river, you start to lose some unwanted material/unstable material -beach: you end up w/ sand (silica) and the cement and unstable materials have been washed away
Composed of gravel-sized clasts -Breccia: comprised of angular clasts -indicates lack of transport processing -deposited close to source
-Conglomerate: comprised of rounded clasts -indicates processing by transport -deposited away from source area
Clastic rock made of sand-sized particles -forms in many depositional settings -quartz is, by far, the dominant mineral in sandstone -Sandstone varieties -arkose: contains abundant feldspar -quartz arenite: almost pure quartz
Composed of silt and clay (siltstone and mudstone) -found far away from continents deep in the ocean - silt sized clasts are lithified to form siltstone -clay-sized particles form shale
Fine clastics are only deposited in non-agitated water -common in deep water basins -organic-rich shales are the source of petroleum
Biochemical and organic rocks
Sediments derived from living organisms -biochemical: hard mineral skeletons -organic: carbon-based residues
Made of CaCO3 shell remains -carbonate grains accumulate in the "cabonate factory" -warm (tropical and subtropical) -normal salinity marine water -wave agitated -oxygenated -shallow and clear
Cryptocrystalline quartz rock -formed from opalline silica (SiO2) skeletons -diatoms -radiotarians -Opalline silica added to bottom sediments dissolves -Silica pore fluids solidify to form chert nodules or beds
Made from organic carbon -Coal: altered remains of fossil vegetation (organic rock on land) -accumulates in lush tropical wetland settings -requires deposition in the abence of oxygen -Oil shale: shale with heat altered organic matter (organic rock in the ocean)
Chemical sedimentary rocks
Comprised of minerals precipitated from water solution
Evaporites: created from evaporated seawater -Evaporation triggers deposition of chemical precipitates -Ex: halite (rock salt) and gypsum
Process: water and salt flow in a stream -water evaporates, while salt precipitates (stays at the bottom) -salt layers form when the sea dries up at times
-A chemical sedimentary rock -Calcium carbonate precipitated from ground water where it reaches the surface -dissolved calcium ion and bicarbonate ion -CO2 expelled into the air causes CaCO3 to precipitate -thermal (hot) springs -caves
A chemical sedimentary rock
Dolostone: limestone altered by Mg-rich fluids -CaCO3 is recrystallized to dolomite -Looks like limestone except... -it has a sugary texture and a pervasive porosity -it weathers to a buff, tan color
A type of chemical sed. rock
Many Varieties: -flint: black or gray from organic matter -Jasper: red or yellow from Fe oxides -Petrified wood: wood grain preserved by silica -Agate: concentrically layered rings
Features imparted to sediments at or near deposition
-Layering (one layer is deposited after another) -Surface features on layers -Arrangement of grains
How are sedimentary structures helpful?
-They are helpful in deciphering conditions at or near the time of deposition
What does the color red mean in terms of rocks?
Red= feldspar -means that the rock has a lot of unwanted materials (ex: clay)
-transformation from one rock to another form
Layering of sedimentary rocks
-Layered= stratified -Arranged in planar, horizontal "beds" -bedding is often laterally continuous for long distances -beds are often similar in composition, color, and texture
= a series of beds
-A sequence of strata that is sufficiently unique to be recognized on a regional scale
Classical depositional environmental setting
-Alluvial fan: base of a mtn. -Delta= end of the river -Middle of the ocean= deep marine environment
-Formed by water flowing over loose sediment -Linked to flow velocity and sediment size -Ripples, cm-scale ridges and troughs, indicate flow -Asymmetric ripples: undirectional flow -Symmetric ripples: wave oscillation -Ripples are commonly preserved in sedimentary rock
Similar to ripples except much larger -form from wind-blown sand in desert or beach regions (both arid & marine environments) -you know if it is a land or marine environment by the types of fossils you find there -often preserve large internal cross-laminations
Created by ripple and dune migration -sediment moves up the gentle side of a ripple or dune -Sediment piles up, then slips down the steep face -the slip face continually moves downstream -added sediment forms sloping cross-bedded layers
Bedding layers that fine upward (coarse at the bottom) -Transition from coarse to medium to fine grain sizes -Abrupt contact w/ overlying coarse base
Do coarse or fine grains settle first when in the air?
-Coarsest grains in the air will settle on the groun first b/c of gravity -Fine grains will settle last
How do graded beds form?
Forms from periodic sediment pulses -sediment added as a pulse of turbid water -as pulse wanes water loses velocity and grains settle -coarsest material settles first, medium next, then fines
1. Sediment breaks loose from a canyon and avalanches down 2. Turbidity current (a cloud of debris) fans out and settles 3. The current comes down and becoms a graded bed
-Multiple graded-beds -Form off the continental slope -Turbidite deposits are found out in the deep ocean and could have oil & gas- companies are interested
Occur after deposition while sediment is still soft -Mudcracks: polygonal dessication -indicate alternating wet and dry conditions -necessitate deposition in a terrestrial setting Scour marks: troughs eroded in soft mud by current flow Fossils: evidence of past life -footprints -shell impressions
Locations where sediment accumulates. They differ in... -energy regime -sediment delivery, transport, and depositional conditions -chemical, phys., and biological characteristics
Depositional characteristics may be inferred from sediments: -continental -transitional -marine
*If there are bigger grains deposited, more energy was used (closer to the coast) *Finer grains are found deeper in the ocean where less energy was used to move them
Terrestrial depositional environments: glacial
Due to movement of ice -ice carries and deposits every grain size (b/c it doesnt have the liquid to sort- everything just gets frozen together and moves w/ the ice-when the ice melts, you have many diff. grain sizes) -creates glacial till; poorly sorted gravel, sand, silt, and clay
-Water carries large clasts during floods -During low flow, boulders are immobile -Coarse conglomerate is characteristic
Terrestrial depositional environments: alluvial fan
Sediments that pile up at a mtn. front -rapid drop in stream velocity creates a cone-shaped wedge -sediments are immature conglomerates and arkoses
Terrestrial depositional environments: sand dune
Wind-blown piles of well-sorted sand -dunes move according to the prevailing winds -result in uniform sandstones w/ gigantic cross-beds
Terrestrial depositional environments: lake
Large ponded bodies of water -gravels and sands trapped near shore -well-sorted muds deposited in deeper water -often capped w/ wetland muds
Terrestrial depositional environments: rivers
Channelized flow transports sediment -sand and gravel fills concave-up channels -find sand, silt, and clay is deposited on flood plains
Depositional environments: marine
Deposited at or below sea-level
Marine depositional environments: deltas
Sediments dropped where a river enters the sea -sediment carried by the river is dumped when velocity drops -deltas grow over time, building out into the basin -often drop a topset-foreset-bottomset geometry
Marine depositional environments: shallow marine
Finer version of beach sediment -fine silts and muds turn into siltstones and mudstones -usually support an active biotic community
Marine depositional environments: shallow water carbonates- tropical
-Skeletons of marine invertebrates -Born in the carbonate factory -Warm, clear, shallow, normal salinity, marine water
Coral is what kind of mineral?
A calcium carbonate
Marine depositional environments: deep marine
Fines predominate far from land sources -skeletons of planktonic organisms make chalk or chert -fine silts and clays turn to shale
Varies across earth's surface -thin to a zero edge where non-sedimentary rocks outcrop -thicken to 10-20+ where the surface has subsided
Sinking of the land during sedimentation -due to crustal flexure and faulting -compounded by the weight of added sediments
Sedimentary basins are important locations for which natural resources?
-coal -petroleum -natural gas -uranium
Where do sedimentary basins form?
-where tectonic activity creates space
Sedimentary basins that form at divergent (pull-apart) plate boundaries -crust thins by stretching and rotational normal faulting -thinned crust subsides -sediment fills the dropped-down basin
Where an oceanic plate subducts under a continental plate -lots of earthquakes occur here
Sed. basins at passive margins
Non-plate boundary continental edge (no earthquakes here) -underlain crust thinned by previous rifting -thinned crust subsides as it cools
Interiors far from margins (within the continent-stretching happened but didnt finish so no ocean formed in between, but space did) -result from differential thermal subsidence -may be linked to failed crustal rifts
Craton side of collisional mountain belt -flexure of the crust from loading creates a downwarp -fills w/ debris eroded off the mountains
Sea level changes and sed. basins
Sedimentary deposition is strongly linked to sea-level Changes in sea level are commonplace geologically -depositional belts shift landward or seaward in response -layers of strata record deepening or shallowing upward Transgression- flooding due to sea level rise -sediment belts shift landward; strata "deepen" upward
3 types of resources consumed in ohio
Metallic, nonmetallic, and energy resources
What is the majority of coal used for?
What do we spend the most/ least on?
1. Coal 2. Limestone and dolomite 3. Sand and gravel 4. Salt 5. Sandstone and conglomerate
Do we spend more on gas or oil?
How has our usage of resources in oh changed from 1985- 2003?
Trend of increasing importance of nonfuel minerals relative to coal, oil and gas (fuel)
Where is coal produced?
East and Southeast ohio (b/c this is where our resources are)
Ohio and coal production/usage
-Produced 2 % of nations coal (14th largest producer in U.S.) -3rd largest coal user in U.S. (90% used for electrical energy) -60% of coal used in OH brought in, mostly from wyoming
What do sedimentary rocks contain that is useful to us?
Oil, gas, and other resources
Trends of sales/value of coal
1990: sales went down but value still went up; then value started to go down with sales and they are both down now
Where are limestone and dolomite mainly produced?
Central and western ohio (franklin co. is one place) -Oh is 8th in U.S. in production of crushed stone -crushed stone is used for road construction and building -Oh 4th in production of lime -lime used for concrete
Is there oil in columbus?
OH sand and gravel production
-Oh 9th in production of sand and gravel -central and sw ohio (64 counties) -used for construction, road construction, concrete
Ice and sediment
-Ice brings up what used to be underneath the surface and when it melts, the sediment is revealed at the surface
Sandstone and conglomerate in ohio
-Produced in E. ohio -crushed for glass sand and aggregate -"dimension stone" for construction -Oh 3rd in U.S. in sandstone ("dimension stone") e.g. orton hall
Salt in ohio
-Most produced in Cuyahoga and lake co. -OH 4th in u.s. for salt production -used for ice control, animal feed, water softening -doesnt employ as many people as other resources (250 vs. thousands)
Oil and gas in ohio
-Produced in central and E. ohio -952 new wells drilled in 2006 -90% success rate, but low flow rates -Production history through 2006: decreasing production but increasing value
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