Final ch.17, 7, 18, 24-25

Question 1

Ch. 17 Plate tectonics

Answer 1

Plate tectonics - scientific theory that describes the large-scale motion of Earth’s lithosphere - theory that Earth’s outer shell is divided into several plates that glide over the mantle

• • For centuries, scientists (usually shunned for doing so) have claimed that earth’s crust is “dynamic”
• –Continental drift –> plate tectonics

Question 2

Brief timeline of continental drift

Answer 2

Brief timeline
	• 1564 - Ortelius - First modern atlas
	• 1858 - Antonio Snider-Pelligrini
		○ Catastrophism
		○ Noah's flood
		○ Fossils
		○ Not popular
		○ Shape and "fit" of the continents was initial evidence
	• 1908 - Frank Taylor
		○ Fit is enhanced by fitting continental shelf at the break and not the shore line

Question 3

Continental drift

Answer 3

Wegner (1880-1930) - meteorologist who started a revolution

• -The predecessor to modern plate tectonics
• • Hypothesis due to similar shapes and fossils
• -Made continental drift maps in 1915 of Pangea - “not widely accepted”

Question 4

evidence for continental drift

Answer 4

Paleoclimate

• -Evidence of extreme climate changes as compared to the present
• —Coal deposits in Antarctica
• —-Evidence from: evaporates, Eolian deposits, coral reefs, glaciation (300Mya)

Paleontological

• –Similar fossils on opposite sides of Atlantic ocean
• – Plants and animals
• • Glossopteris on all southern continents (largest and most well known extinct ferns)
• – No mechanism to transport them across the ocean
• -Ancient Mosasaurs habitat (fossils in BOTH South America and Africa on opposite sides…where it would have split) - like a mini lizard crocodile
• –Permian freshwater reptiles

Rock types and structures

• –Distinct rocks on both sides of the ocean
• -Cape fold belt and equivalent - S. Africa and —Appalachian Mtns. And equivalent - US, Canada, Scotland and Norway
• –Only occur in rocks > 145 Mya

Question 5

development of plate tectonic theory

Answer 5

Wegener’s theory received?

• -“less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories” - its appeal lies in the fact that it has few restrictive rules
• -“author offers no direct proof of its verity” - “Facts and principles opposed to it have been ignored”
• -“it is an impossible hypothesis!!”
  • Original evidence for the CONTINENTAL DRIFT was from the continents
  • Tech. advances in 1950s and 60s allowed for investigation of sea floor
  • Geophysics and paleomagnetism provided new data
  • Seafloor spreading proposed by Hess in 1962 - considered new data on ocean floor

Question 6

geology of ocean floor

Answer 6

Topography of the ocean basins

• –Basins are divided by a large ridge system
• – Ridge system is continuous around the entire globe
• –Central rift valley within the ridge

Physical properties

• –Composed of basalt
• -Younger and thinner than most continental rocks
• –No evidence of crustal deformation - FOLDED MOUNTAINS

Seafloor spreading proposed 1960 - Hess

• • Proposed mechanisms
• • Mantle convection
• –Rifting and volcanism along ridge system
• -Continents pushed along –Recycling of oceanic crust by subduction

Question 7

Polar wandering

Answer 7

• –Earth’s north magnetic pole moved
• –Polar wandering paths varied by continent
• –But multiple poles are not possible

Magnetic reversals

• –Earth’s magnetic field polarity has reversed through time
• –Normal polarity - N(magnetic) = N(geographic)
• –Reversed polarity - N(magnetic) = S(geographic)
• -At least 12 reversals in last 4 million years

Vine and Matthews (1963) tested Hess’s hypothesis using magnetism

• -Magnetic polarity reversals recorded in ocean floor
• –Magma cools forming new crust
• –Polarity at time of cooling preserved

Magnetic polarity stripes in ocean crust parallel ridges

• –Symmetrical on either side of the ridge
• –Give age of seafloor
• -Rates of plate motion may be calculated
• –Youngest sediments resting directly on basalt near the ridge
• –Sediment just above the basalt gets older moving away from the ridge
• -Accumulation rates of approx. 3 mm per 1000 years

Question 8

Plate boundaries - divergent

Answer 8

Plate margins
--Lithosphere divided into plates
---Structural features, not land and ocean
---Ridges, trenches and mountains
---
Not permanent

DIVERGENT PLATE BOUNDARIES

• -plate splits and pulls apart - almost all are submerged under sea
• -zone of spreading —> rifting and continent splits
• -As continents separate, new oceanic crust and lithosphere is formed and ocean bsin becomes wider
• -tensional stresses that produce NORMAL FAULTS along margins of separating plates - magma injected up, cools and becomes part of moving plates
• -some of most active VOLCANIC areas on earth
• -Mid-Atlantic ridge

–Oceanic-oceanic crust
○ Mid-oceanic ridge with central rift valley
○ Surface covered with lava flows and pillow basalts
○ Fissures are parallel the ridge axis
○ Hydrothermal vents form chimney structure
○ Unique ecological community
—Continental-continental crust
○ Rift valley
§ East African Rift valley
○ Causes sea floor spreading as the plates diverge across
○ Forms a Mid-ocean ridge

Question 9

convergent plate margins

Answer 9

plates collide and one moves down into the mantle - lots of igneous activity - earthquakes, metamorphism, mountain building

Oceanic-oceanic

• – Volcanoes in an ISLAND arc
• –Japan
• -one is thrust under called SUBDUCTION - marked by deep sea trench - into asthenosphere where heated and absorbed into mantle

Oceanic-continental

• -Subduction zone
• -Volcanoes in a –Cascade range
• -lighter crust resists subduction and overrides oceanic plate - may form mtn. belt - roots with magma

Continental-continental

• –Intensely folded/faulted mountain belts
• –Metamorphic rocks dominate
• • Igneous rocks included
• -neither can subside into mantle…makes high mountain range - Himalayan man.

Question 10

transform fault margins

Answer 10

Transform faults are large vertical fractures or faults in the crust

• -zones of SHEARING plates slide past without creating or destroying lithosphere
• -occur along transform fault - which is strike-slip fault btwn plates - movement is horizontal and parallel to fault
• • Movement is side to side
• –May extend for long distances
• –In oceanic crust, deep valleys are formed
• –May extend onto continents
• -San Andreas Fault (California)

Volcanic hotspots in Hawaii - Yellowstone - Bermuda

Question 11

plate motion - rates and mechanisms

Answer 11

wo ways to look at plate motion

1. Relative velocity - the movement of one plate relative to another
2. Absolute velocity - compares plate movement to a fixed position
   - –Hotspots

Tectonic mechanisms - convection of heat from the core and mantle drives tectonics

• -Layering at 660 km
• –Convection of heat from the core and mantle drives tectonics
• –Slab pull
• –Ridge push

Question 12

reading key points - ch. 17

Answer 12

• -Transform plate boundary connecting the Caribbean trench with the Middle Am. trench - on order is ridges and valleys, high plateaus, grabens, and volcanoes
• –Theory of continental drift was proposed in early 1900s and supported by geological evidence - lack of knowledge of nature of oceanic crust prevented the complete theory to be developed

Major breakthrough in development of plate tectonics theory occurred in 1960 when the topography of the ocean floors was mapped and magnetic and seismic characteristics of oceanic crust were determined

Question 13

pt. 2 reading key points - ch. 17

Answer 13

Most tectonic activity occurs along plate boundaries

Direction of relative motion of plates is indicated by

• –A trend of the oceanic ridge —Seismic data
• –Magnetic stripes on the seafloor
• –Ages of chains of volcanic islands and seamounts
• –The motion of a plate is described in terms of rotation around a pole
• –Heat from the mantle (generated by radioactivity) and from the core is probably the fundamental cause of Earth’s internal convection

The major forces acing on plates are
○ Slab-pull
○ Ridge-push
○ Basal drag
○ Friction along transform faults and subduction zones
○ Most imp. Are slab-pull and ridge push in making plates move

Question 14

continental drift

Answer 14

Theory considered as profound as Darwin of biology and Copernicus with the sun as center
—Predecessor of plate tectonic theory was continental drift - after world maps were created, Scientists could see continents (S Am. And Africa) that fit together like puzzle - Antonia Snider-Pelligrini put continents together - also looked at fossil evidence I N Am. And Europe that were on opposite sides like they had been together

Alfred Wegener, German - was first to seriously investigate theory of continental drift - based on shapes of continents and geologic fossil evidence in Brazil and Africa - he drew map of three stages beg. With large mass called Pangaea (“all land”)

• –He thought less dense silicic continental rock plowed through denser rocks of ocean floor driven by forces related to rotation of the earth
• –Most rejected his idea - some geologic evidence supported

Question 15

paleontological evidence for continental drift

Answer 15

• –Fossils of land animals were found on both sides of Atlantic…would be unable to cross so must have been connected
• –Specifically fossils of Glossopteris, a fernlike plant found in rocks of same age from S Am., S Africa, India and Antarctica - could not have been transported by wind bc too large
• –Also reptile Lystrosaurus - same period - S continents, Antarctica, Asia
• –Also geologic factors end abruptly at coast of one continent and cont. at another facing across Atlantic - folded mountain ranges at Cap of Good Hope at S tip of Africa appear in similar age and style near Buenos Aires, Argentina - folded Appalachian mountains also (E US and similar in Ireland, Scotland, Norway)

During latter part of Paleozoic Era (300M years ago), glaciers covered continents in S Hemisphere and all continents show evidence of glaciation - however, today all continents except Antarctica are near equator where glaciation could never occur

• –Glaciers cannot occur in the ocean, they originate on land and move toward edge of continents!…so bc there is evidence of glaciation on various continents…they must have been anciently concentrated in one area
• –Coal in Antarctica shows that abundant plant life once was there - now covered in ice

Just lots of evidence of climate change (due to moving) in the salt, rocks, reefs

• –Wegener was criticized bc he failed to explain what forces would permit continents of granite to plow through oceans of rock - theory was not developed further until WWII
• –Theory - continents grouped together at end of PALEOZOIC ERA

Question 16

developing theory of plate tectonics

Answer 16

Continental drift theory was supported…but diff. to accept completely bc no effective way to study the ocean floor - Early 1960s bc new instruments allowed scientists to map the topography of the ocean floor and study it
—Echo-sounding devices to study ocean floor topography - revealed several ocean basins are divided by a great ridge…65,000 km long - at the crest of the ridge is a central valley which is a rift valley that is splitting apart under tension (LONGEST MOUNTAIN RANGE ON THE PLANET)

Showed diff. btwn continental and oceanic crust - ocean crust is YOUNGER and THINNER, composed of basalt…so diff. composition than granite continental crust - oceanic crust not folded mountain structures so not subjected to strong compressional forces putting weight on the crust
—1960, Hess proposed theory of seafloor spreading using echo soundings data and continental drift theory
Argued they are spreading apart by convection currents in the mantle - moving away from oceanic ridge and towards deep-sea trenches where oceanic crust descends back into the mantle and is reabsorbed - spreading produces fractures in crust where magma from mantle shoots up to become new oceanic crust (ocean floor is regenerated every 200-300 M years)

Question 17

Paleomagnetism

Answer 17

Earth has internally generated magnetic field - magnet with N and S magnetic pole

• –Electromagnetic/dynamo theory - outer core of liquid iron convects and the motion generates electrical currents that establish a magnetic field
• –Began by studying rocks - basalt is rich in iron and becomes magnetized by earth’s magnetic field as they cool
• –The mineral grains therefore become “fossil” magnets to show orientation of earth’s magnetic field during time of cooling - preserve record of paleomagnetism
• –Also works in iron-oxide grains in sandstones of sedimentary rocks

These rocks show that earth’s north magnetic pole has steadily changed over time - N magnetic pole has moved Northward and Westward to where it is today

Question 18

Poles moving throughout time

Answer 18

Most logical explanation is that there has always been only one magnetic pole that has been fixed, while the continents moved with respect to it –> paleomagnetism data supports theory of continental drift

• –Also studying magnetic properties of volcanic rock shows that polarity of earth’s magnetic field has reversed many times over history
• –Normal polarity - periods when magnetic field was oriented as it is today with N magnetic pole in N and close to current position
• –These periods have been followed by periods when locations of N magnetic pole and S were reversed - called reverse polarity, which began 2.5M years ago - present period of normal polarity began 780,000 years ago

Polarity chrons - the major intervals of alternating polarity (1M years apart)
—Used paleomagnetism to test Hess’s theory of seafloor spreading - thought that if it had occurred it would be recorded in the magnetism of basalts in oceanic crust

—If it had reversed, new basalt forming at the crest of oceanic ridge would be magnetized according to polarity at time it cooled - as ocean floor spreads it would show symmetrical series of magnetic stripes (alternating reverse and normal polarities)
○ Also imp. To note that patterns of magnetic stripes on the ocean, on either side of ridge, match the patterns found in a sequence of recent basalts on continents (shown in continental rocks too)

Compelling evidence that seafloor is spreading and of continental drift
– Imp. Bc help determine age of seafloor and measure rates of plate movement

Question 19

evidence from sediment on ocean floor

Answer 19

Some of most convincing evidence for plate tectonics comes from recent drilling in sediment on ocean floor - deep sea drilling project starting in 1968 with Glomar Challenger ship

• –Confirms conclusions from paleomagnetism studies by samples of fossils accumulated on diff. portions of ocean floor
• –Similar to predictions of plate tectonics theory - the YOUNGEST sediment resting on basalt of ocean floor is near oceanic ridge, where new crust is created - older rocks also thicker!

Away from ridge, becomes progressively older - oldest near coast of continents - the oldest rocks on ocean floor are 200M years old but continental crust rocks can be 3.8B years old
—Certain types of sediment increase floor spreading - plankton can only survive in warm, nutrient rich water near equator - when they die, their skeletons create layer of soft, white chalk on seafloor - but have found evidence of chalk layer north of today’s equator in Pacific…evidence seafloor has spread

Question 20

plate geography

Answer 20

Plate boundaries reflect earth’s internal dynamics - are most significant geologic elements - to understand their location, have to pay attention to earth’s structural features
—ectonic plates - earth’s outer rigid lithosphere is divided into 7 major plates and several smaller sub-plates
○ Major plates outlines by oceanic ridges, trenches, and young mountain systems
○ Pacific, Eurasian, N American, S American, African, Australian, Antarctic plates
§ Continents are not moving separately from oceanic crust…both parts are moving lithospheric plates that extend into mantle
○ Largest is Pacific plate, covers 1/5 of earth’s surface and mostly composed of oceanic crust - other large plates contain both oceanic and continental crust

Indiv. Plates are in constant motion and cont. change in size and shape - plates without continental crust can be completely consumed in subduction zones
Plate boundaries
–Plates move together - if one part moves, the whole plate moves - nearly all major tectonic activity occurs along plate boundaries

Question 21

plate motion

Answer 21

So rotation around imaginary axis
— Plate 1 moves around the axis AR (Axis of plate rotation), one pole of which is the point P (pole of rotation)

Diff. parts of a plate move at diff. velocities - max. velocity near equator of rotation and min. velocity at poles of rotation - pole would have zero velocity bc it is a fixed point around which the plate moves - gets higher as reaches equator

Direction of movement is determined multiple ways

• –Trends of oceanic ridge and transform faults are related to location of pole of rotation
• –Pacific plate is moving NW direction - bordered by several small plates of subduction zones

IMP: plate margins are not fixed but can moves as much as plates themselves - Antarctica and Africa plates are enlarged as new lithosphere generated but no subduction zones so ridges are moving outward
—If 2 divergent plate boundaries are not separated by subduction zone - new lithosphere is formed so have o spread and move apart

Question 22

rates of plate motion

Answer 22

Rates determines in 2 ways
—Think of 2 cars driving 50 km/hr - their relative velocity is 100 km/hr but compared to your fixed position, cars have an absolute velocity of 50 km/hr

1. Relative velocity - compares the movement of one plate with respect to another plate
   - -To determine need to know
   - –Transform faults show direction of movement
2. Absolute velocity - compares plate movement to a fixed reference frame
   - – If we assume that hotspots are stationary, then the tracks of hotspot volcanoes are tangible records of a plate’s absolute velocity and its direction of movement
   - –Can be measured directly using satellites and lasers
   - –The velocities and directions measured are complementary records of plate movement - plates are moving at diff. rates
   - –Think of relative movement of Africa with respect to Europe
   - –Relative movement -Europe is S towards Africa since separated by subduction zone

However, absolute motion of both plates is Northward - Europe is moving slower than Africa so a convergent margin has developed btwn them
Fastest moving plates have a large plate of the plate boundary as a subduction zone - slower moving plates lack subduction boundaries

Question 23

driving mechanisms of plate tectonics

Answer 23

Ultimately energy that drives plate tectonics is heat transported out of hot core and mantle to earth’s surface - type of convection and result of earth’s effort to cool and reach thermal equilibrium

One of 1st models - convection cells within mantle carried plates - that plates played little or not active part in the convection

• -Convection mantle would cause lithosphere to split, and moving mantle would carry lithosphere toward subduction zone
• • Distance btwn plate boundaries thought to be caused by size of convection cell
• –More successful model of convection theory says plates are active participants in convection process
• • Lithosphere is cold upper layer of convection cell - bc of greater density, lithosphere sinks - subduction occurs not bc plate is pulled down by descending mantle but bc the plate becomes denser than the underlying asthenosphere
• –Upward flow from asthenosphere is caused by plates spreading

Question 24

forces that influence motion of plates (PICTURE!) - Slab pull, ridge push

Answer 24

1. Slab-pull
   - –Pull exerted on plate as the dense oceanic slab descends under its own weight into asthenosphere in a subduction zone - slab sinks bc it is denser than the asthenosphere and it pulls the rest of the lithosphere with it
   - –Major driving force!!! - bc inc. amt. of subduction zones = inc. velocity
   - — Denser area (happens in Hawaii) sinks, bc cooler and denser, which pulls solid crust apart - large slabs of crust break and split, causes molten lava to rise from below and create zone of new cooling crust
2. Ridge-push
   - –Gravity makes lithosphere slip off elevated edge
   - –2nd most imp. Factor of tectonic plates -related to elevation of the ridge
   - –Asthenosphere acts as slippery layer beneath the slab and lithosphere slides downhill

Question 25

forces that influence motion of plates (PICTURE!) - basal drag, mantle resistance, friction

Answer 25

3. Basal drag
   - –Resistance to flow exerted on bottom of plate by underlying asthenosphere; shear at base of plate
   - – Depending on direction of flow in the asthenosphere, this could aid or hinder plate movement
4. Mantle resistance
   - –Frictional resistance to movement of subducting plate through asthenosphere and mesosphere
   - –Seems to be the MAJOR resisting factor - slows movement
5. Friction
   - –Resistance along transform faults and btwn converging slabs of lithosphere in a subduction zone - shear btwn 2 plates
   - –Forces driving plates are balanced by forces that resist their movements - so forces provided by slab-pull an d ridge-push are balanced by resisting forces of basal drag, mantle resistance and friction
   - –Absolute velocity of a plate is strongly related to the proportion of its margin that is subducting
   - -Ex. Pacific plate has 40% of margins in subduction zones so has high velocity

Question 26

Ch. 7 earthquakes key notes

Answer 26

• – Earthquakes might be the most convincing evidence that the crust is moving - crust vibrates and is broken
• –From geologic studies beginning 200 years ago, show that rock layers in certain parts of continents are folded, fractured and deformed on gigantic scale - deformation of crust is most intense in great mountain belts, where sedimentary rocks were originally horizontal but now folded, contorted, fractured and overturned (Appalachian, Rockies, Andes, Himalayas, Urals and Alps) show folded deformation

Evidence of moving lithosphere and deformation it produces

• –Deformation of earth’s crust is well documented in historical times by
• –Earthquakes along faults , Raised beach terraces
• -Rocks deform when applied stress exceeds their strength - may deform by ductile flow or brittle fracture - extensional stress causes rocks to shorten and thicken

Question 27

Rock deformation

Answer 27

Rocks deform in response to differential stress - resulting structure depends on the stress orientation
— High temp = ductile flow of rocks occurs, low temp. = brittle fractures

Force applied to an area called stress - same as pressure and is a measure of the intensity of the force or how concentrated the force is

• –Solids deform/bend/or break if the stress exceeds their strength (natural resistance to deformation)
• -All rocks are under stress - but if stress is equal in all directions does not bend - differential stress is when magnitude of stress is not same in all directions and rocks deform - change I shape called strain

Question 28

two ways rocks deform

Answer 28

1. Brittle deformation, or fractures
   - – Breaking into pieces - seen in common solids: chairs, pencils…break if too much force applied
   - -fracture - stress exceeds docile limit - irreversable break
2. Ductile deformation
   - –When rock body deforms permanently without fracturing or losing cohesion
   - –Most common is vicious flow of fluids, like magma - solids also can bend (metal) - can make dents, not fractures - solid flow called plastic flow - slow creep as materials change
   - – Mineral grains flow and recrystallize
   - -irreversible change in size or shape

Depends on temp. and pressure of surroundings and rate at which stress is applied

• – Low pressure, low temp., rapid deformation –> brittle structures - common in shallow crust
• –High confining pressures, high temp. and low rates of deformation –> ductile more common in mantle and deeper parts of crust

Glass - when cold it breaks and is brittle, when hot it can bend
—Timing - warm taffy is pulled slowly it will be ductile and stretchy, but if cold and pulled quickly can snap into pieces

Rocks - flow of rocks in solid state to form folds in metamorphic rocks is ex. Of ductile

• –Tension - occurs where stresses point away from one another and tend to pull rock body apart
• -Compression - tends to press body of rocks together

Question 29

3 types of deformation occur bc differential stresses caused by tectonics

Answer 29

1. Extension
   - –Two adjacent blocks move away from each other - caused when diff. stresses point away from one another
   - –Result is lengthening and common at divergent boundaries
   - ——Brittle rocks - expressed by fracturing and faulting
   - ——Ductile rocks- stretching and thinning
   - -tensional - pulling apart - extensional stress leads to stretching and thinning
2. Contraction
   - –Towards each other - when diff. stresses are directed toward one another
   - –Common at convergent boundaries - result is shortening and thickening of rock bodies
   - ——Faults in brittle and folds in ductile
   - -compressional like sqeezing together - shrotening and thickening
3. Lateral-slip
   - —Slip horizontally past one another
   - –Type of shear (term for slippage of one block past another on a fracture) - dominates transform boundaries
   - -shear - slipping, twisting or wrenching - causes a lateral shift

STRAIN is the change in the shape of colume of a rock that resutls from STRESS

Question 30

Dips and strikes in rock structures

Answer 30

• –Orientation of planar features in rocks, bedding planes, faults, and joints are defined by measurements of:
• -structures are defined by orientation of planes

Dip - the downward inclination of plane - the angle and direction of inclination from the horizontal

• -the angle from horizontal
• -dip direction - the compass bearking down-dip

Strike - the direction or trend of the plane - the compass bearing of a horizontal line on the plane, such as the bedding plane or fault (PICTURE OF THEM on pg. 180)

Both are measured with a geologic compass - measures direction and angle of inclination
—Measured by rule of Vs - each V points in direction of bed slips

Question 31

Joints

Answer 31

fractures created by tension of brittle rocks - no shear or displacement

• -form by cooling of igneous rocks
• -tension fractures in brittle rocks along which no shear has occurred - they form at low pressure and are found in almost every exposure
• –Simplest and most common structural features of rocks - cracks or fractures called joints - most imp. Feature is the absence of a shear

Form at low pressure as stress accumulates and exceeds rock’s strength

• —Common to see multiple sets of joints that intersect at 45 and 90 degrees
• –Divide rock bodies into large rectangular blocks
• –Best areas to study them are where brittle rocks, like thick sandstone, have been fractured and their joint planes accentuated by erosion
• –Expressed by deep, parallel cracks that have been enlarged by erosion - most impressive from birds eye view in the air
• –Joints control the development of stream courses

Have great economic importance
○ Can be paths of groundwater migration and the movement and accumulation of petroleum
○ Control deposition of copper, lead, zinc, mercury, silver, gold
○ Hot solutions of minerals crystalize along joint walls, forming mineral veins
○ Can be an asset or an obstacle - closely spaced joints limit size of blocks that can be removed - but the expense of removing blocks is reduced and waste is held to a min.

Question 32

faults

Answer 32

Fractures along earth’s crust along which displacement has occurred - slippage (shear) along brittle fractures of earth’s crust creates faults - form by differential stress - grow from a series of small movements, which occur as stress built up in crust is suddenly released in earthquakes - also occurs by slow tectonic creep

3 types of faults - normal, reverse, strike-slip

movement along faults during earthquakes rarely exceeds a few meters

• -slow shifting also accors along fault plane in Cali - called tectonic creep
• -breaks buildings across fault line - shows movement does not only occur during one violent event

Question 33

normal faults

Answer 33

usually result of extension (pictures on 184!!!)

• –Created by tension - RIFTS are created by normal faults
• – Rocks above the fault plane (hanging wall) move downward in relation to those beneath the fault plane (the footwall)
• –Vertical movement produces a cliff, or scarp, at the surface
• – If dips at low angles called detachment faults

Usually not isolated - group of parallel normal faults together - narrow bock btwn 2 normal faults called a graben (usually forms a fault valley or basin with straight, parallel walls) and upraised block is a horst (form plateaus bounded by faults) (look at pics on 186!!!)

• –Usually juxtapose younger rocks over older rocks - if strata not included called “omission of strata”
• –Large scale normal faulting is result of horizontal extensional stress - stretches, thins, and pulls apart the lithosphere

Normal faults are COMMON bc rocks are weaker during extension than compression - usually at divergent plate margins

• –So normal faults are dominant along oceanic ridge, in continental rift systems and at continental margins
• –In Basin and Range province of W N Am., normal faults produce grabens and horsts in Mexico to Oregon and Idaho - forms high mountain ranges
• -Also Wasatch Fault in Utah

Question 34

reverse faults

Answer 34

thrust faults - usually result of horizontal compression

• –Faults where hanging wall moved up and over the footwall
• –Thrust faults - low angle reverse faults and dip at angles less than 45 degrees - movement is horizontal - common in large mountain ranges
• –Occur from horizontal compression with max stress perpendicular to trend of fault - this shortens and thickens the crust
• –Usually put Old over younger strata and instead of omitting layers, units repeated in vertical section
• –Mostly develop at convergent plate margins - usually associated with folds and prominent in all of world’s major mountain belts (evolution from folds on pg. 187!!)

Question 35

strike-slip faults

Answer 35

result of lateral slip

• –High angle faults along which slip is horizontal. Parallel to the strike of the fault plane - principle movement is HORIZONTAL - caused by shear stress
• –Usually no vertical movement, so high cliffs not common - expressed by straight valleys or series of low ridges
• -No crustal thinning or thickening produced - except at bends in fault where extension and contraction can occur

Result: offset of the drainage patterns - shown by abrupt right angle bends in streams at the fault line - as faults move, some parts may become small ponds
—-Also disrupt patterns of groundwater movement - reflects in contrasts of vegetation and soils
○ Most famous is Cali San Andreas Fault
○ Also join adjacent segments of mid-ocean ridges

Question 36

Folds

Answer 36

• Warps in rock strata during ductile deformation - most occur at convergent plate boundaries by horizontal compression where crust is shortened and thickened - usually HORIZONTAL COMPRESSION
○ Broad open folds form in stable interiors of continents
• T3D structures ranging from small crinkles to large domes and basins
• Almost every exposure of sedimentary rock shows some evidence that strata has been deformed - some tilted, deformed, folded like wrinkles
• Warps in strata called folds - manifestation of ductile deformation - also called contraction
• Form slowly over millions of years as rock layers gradually yield to differential stress and bend
• Economic importance bc they commonly form traps for oil and gas and control localization of ore deposits
• Folds are described by: the strike of their hinge line and the angle of dip of their limbs

Question 37

three types of folds

Answer 37

1. Anticline
   - – Up-arched strata, with 2 limbs (Sides) of fold dipping away from the crest (like an A! for anticline)
   - –Rocks in eroded anticline are progressively OLDER towards interior of the fold
2. Synclines
   - –Down-folds - or troughs - with limbs dipping towards center (like a smile!!!)
   - –Rocks in center are younger toward center of the fold
3. Monoclines
   - – Folds that have only one limb - horizontal or gently dipping beds are modified by simple step-like bends

Hinge plane - divide simple fold into 2 or less equal parts by imaginary plane (look at pic on 192!!!!!)
—Hinge parks region of maximum curvature in fold
—Line formed by intersection of hinge plane and bedding plane is hinge line and downward inclination of hinge line called a plunge
§ Plunging fold - Fold in which hinge line is inclines
— In most, the hinge plane is not vertical but inclined - one limb is steeper than the other

Question 38

domes and basins

Answer 38

occur in continental interiors where sedimentary rocks coveringhave been warper into domes and basins
–rocks in central part of eroded domes are oldest - rocks in centers of basins are youngest (194 pic@@)

diapirs

• -some domes and basins form by vertical adjustments caused by density diff. in crust
• -small domes with rise of less dense material than overlying rock work way upward
• -thick sequences of sedimentary rocks may deform and rise as diapirs - the streamlined bodies that look like teardrops! (194)
• -salt and also magma

Question 39

complex fold belts

Answer 39

Where contraction is intense (usually orogenic belts at convergent plate boundaries), sedimentary rock layers are deformed into a series of tight folds in long linear belts
—Orogenic belts are a long linear series of folds
—Fold geometry is not overly complex - pattern of outcrops may appear complex
—Complex folds: re-folded, cut by thrust faults - complex due to application of shear stress, multiple folding events
• Folds resemble wrinkles in a rug - complexity of crop patterns due to erosion, so some folds are diff. to recognize without experience and observation
• Intense deformation in mountain ranges produces complex folds - some folds are refolded during millions of years of deformation
• Overturned fold - is huge anticlinal structure with numerous minor anticlines and synclines forming indentations on the larger fold
• Plunging folds - occur when folds axis is dipping or plunging
○ Limbs of some folds are not the same, one dips more steeply than the other
○ Some folding so extreme that beds are turned upside-down

Question 40

rock deformation definitions

Answer 40

stress is the force acting on a rock to deform it

• –Uniform (confining) stress is equal in all directions - Rocks are confined by the rock around them
• –Differential stress is not equal in all directions - this is what deforms rocks

Question 41

18. reading notes

Answer 41

• • Earthquakes more than any other phenomenon demonstrate that earth continues to be a dynamic planet - constantly changing by internal, tectonic forces
• –Most earthquakes occur along plate boundaries - as the plates move, these boundaries (ocean ridges, continental drifts, subduction zones, and transform faults) are sites of most intense earthquake activity - occur during sudden movements along faults
• -Earthquakes can tell us about present plate motion but also seismic waves provide effective probe of Earth’s interior - primary data to understand earth’s internal structure

Seismic waves are vibrations of earth caused by rupture and sudden movement of rock

Exact location and timing of earthquake cannot be predicted - but seismic risk can be evaluated and high risk areas can prepare for future earthquakes

• –Divergent plate boundaries and transform fault boundaries produce shallow-focus earthquakes - convergent boundaries produce an inclined zone of shallow-focus, immediate focus and deep focus earthquakes
• -The velocities at which P waves and S waves travel through the earth indicate that earth has a layered internal structure based on composition - crust, mantle and core

Also has a solid inner core, a liquid outer core, a weak asthenosphere and a rigid lithosphere
–Plate tectonics and upwelling and downwelling plumes are the most imp. Manifestations of earth’s internal convection - the magnetic field is probably caused by convection of the molten iron core

Question 42

characteristics of earthquekes - elastic rebound theory

Answer 42

Vibrations of earth - caused by rupture and sudden movement of rocks that have been strained beyond their elastic limits
–Aaron’s pretzel ex. - the transform plates sliding next to each other are not smooth…its like two pretzels and the salt rubbing creates tension until it snaps and the salt pieces fall off - similar in earthquakes

Elastic rebound theory

• –The origin of earthquake explained by bending a stick until it snaps - energy is stored in the elastic bending and released if rupture occurs - which causes the ends to vibrate and send out waves
• –Along San Andreas Fault - railroads, fence lines, streets are deformed at first as strain builds up and offset when movement occurs at fault, releasing the elastic strain - sections of the fault can be locked together until enough strain accumulates to exceed the rock’s elastic limit and cause displacement

Focus - point WITHIN Earth where the initial slippage generates earthquake energy - point of initial movement on the fault - seismic waves radiate from the focus
—Epicenter - the point on earth’s SURFACE directly above the focus

Question 43

types of seismic waves

Answer 43

Seismic waves are generated by earthquake shock - each type travels at diff. speed and arrives at a seismograph 100m away at a diff. time

1. Primary waves - the first waves to arrive (P waves)
   - –Compressional wave, identical in character to sound waves passing through liquid or gas
   - –Wave transmits energy by compressing and dilating the material through which it moves - wave particles move forward and backward in direction of wave travel
   - –Have smaller amplitudes than later waves
   - -travel through solids and liquids - compressional waves
2. Secondary waves (S waves)
   - –Second waves to arrive - oscillate back and forth at right angles to the direction of wave travel
   - –Shear waves bc slide past each other - cannot move through liquids
   - –Cause a second burst of strong movements to be recorded by seismograph
   - -travel through solids only - transverse (shear) waves)
3. Surface waves - last waves to arrive
   - –Travel slowly over earth’s surface
   - –Particles involved in one type of surface wave move in orbits, similar to particles in water waves
   - -have L waves (love) and R waves (Rayleigh)

Greater distance btwn seismic event and a recording station, more time it takes for first wave to arrive - also longer interval btwn arrival of P and S waves

• –Time of arrivals btwn P waves and S waves is correlated with the distance btwn seismic event and recording station
• –Find the epicenter of an earthquake by comparing the arrival times of P and S waves at three seismic stations

Question 44

earthquake locations - shallow-deep

Answer 44

Location imp. Bc indicates depth at which rupture and movement occur

• –Earthquakes grouped by depth focus
  1. Shallow-focus earthquakes - occur from surface to depth of 70 km
• –Occur in all seismic belts and produce largest % of earthquakes

2. Intermediate-focus earthquakes - occur btwn 70 and 300 km below surface
3. Deep-focus earthquakes - btwn 300 and 700 km
   - –Intermediate and deep are limited in # - confined to convergent plate margins
   - –Max energy released by an earthquake is smaller as the depth of focus increases
   - –Seismic energy below 70 km is weakened by the time it reaches surface - so most large earthquakes have a shallow focus
   - –Depth calculated from the time that elapses btwn arrivals of 3 major types of seismic waves

Question 45

intensity

Answer 45

Intensity or destructive power of earthquake is evaluation of the severity of ground motion at a given location - destruction described in terms of damage caused to buildings, bridges, other - intensity based off observation
• Intensity at specific location depends on several factors
○ The total amt. of energy released
○ The distance from the epicenter
○ The type of rock and degree of consolidation
Amplitude and destruction are greater in soft, unconsolidated material than in dense, crystalline rock

MERCALLI INTENSITY SCALE - based on observation (I- XII)
–how many people felt it - panic - total damaga

Question 46

magnitude

Answer 46

Magnitude is objective measure of the amount of energy released - much more precise measure than intensity
• Based on direct measurements of the size (amplitude) of the seismic waves, made with recording instruments, not observations of destruction
• Total energy released from an earthquake - calculate from the amplitude of the waves and the distance from the epicenter
• Richter scale - assigns a single number to an earthquake - each step on the scale represents an inc. in wave amplitude by a factor of 10
○ Earthquake with magnitude of 2 is 10x as great in amplitude as an earthquake with magnitude of 1 - vibrations of earthquake with magnitude of 8 are 1M times as great in amplitude as those of earthquake with magnitude 2
○ Inc. in total energy released is 30x for each step on the scale
——Largest earthquake ever recorded was magnitude of 8.8 on Richter scale (larger not likely bc rocks not strong enough to accumulate more energy)
• Modified by moment magnitude scale - most common today - reflects the amt. of energy released by an earthquake - magnitudes reported in media use this
○ Calc. magnitude of ancient earthquake using the amt. of slip along the fault scarp
Moment magnitude is greater than the Richter magnitude - largest known moment magnitude was 9.5

Question 47

earthquake hazards - prev. earthquakes

• -SF
• -Alaska
• -China
• -Cali
• -Japan
• -Turkey

Answer 47

Primary effect is ground motion can shear and collapse buildings, dams, tunnels - secondary effect is soil liquefaction, landslides, tsunamis, and submergence of land

San Fran 1906
○ Most destructive earthquake in the history of the US - shallow earthquake on transform plate boundary - lasted only one minute and had magnitude of 8.2
—- Fire following caused most destruction and loss of 700 people
— Major visible impact on San Andreas Fault zone - horizontal displacement
— Picture of the train tracks completely moved over

Alaska, 1964 - 9.2
○ Convergent boundary - crustal deformation was most extensive ever documented - but less casualties bc fewer ppl live there
○ Landslides triggered destructive tsunamis - also fires

Tangshan, China - 1976 - 7.8 with aftershock of 7.1
○ 2nd most devastating earthquake - city demolished in seconds
○ HUGE aftershock that was surprising - killed 240,000 people

Northridge, California (N of LA) - 1994 - 6.6
○ With thousands of aftershocks

Kobe, Japan - 1995 - 7.2
○ In monetary terms, largest disaster in history - $140B in destruction

Question 48

earthquake prediction

Answer 48

Effective short term earthquake prediction is not possible currently - preparation is achievable goal
—More than a million occur around the world each year - about 50 are large enough to cause property damage and loss of lives

Chinese scientists claim to be successful in predicting about 15 earthquakes in recent years

• –In spite of fact that there is no scientific evidence that animals can sense advent of an earthquake, Chin. predictions rely heavily on idea that animals sense underground changes before an earthquake and behave abnormally
• –Chin. Scientists predicted the large (7.3) Haicheng earthquake in 1975 - in 1974 the water table in region periodically rose and fell - ground tilted in some places - bizarre when snakes came out of hibernation and froze to death and groups of rats appeared suddenly - began evacuating and when it hit more than 90% of houses collapsed - preparation spared thousands of lives

Question 49

seismic gap theory

Answer 49

Huge facility in Parkfield California devoted to predicting earthquakes - but has failed

• –Now focus on calculating the probability than an earthquake of a certain magnitude will occur in a certain period ranging from decades to centuries
• –Forecasting also includes compilation of maps showing seismic potential of major plate boundaries, where expected to occur in future
• –Along plate margins are gaps in seismic activity where stress may be building to a critical level

Seismic gap theory - probability of a major earthquake from 1968-2018 on San Andreas Fault

Question 50

preparation

Answer 50

• Understand where they have happened in the past with assumption that they will strike there again in future
○ Use seismic risk map - for US - shows areas along plate boundaries that could be building up stress and be sites in the future in red - grey areas are where earthquakes have relieved strain within last 40 years
• Put critical facilities (schools, hospitals, fire stations) in areas where less likely - have restrictive building laws
1. Check for hazards inside home - objects that could fall
2. Learn how to turn off utilities at house - flexible gas lines should be used to avoid breaking
3. Have disaster supplies on hand (flashlight, food, water, first aid, blanket)
4. Have emergency communication plan to reunite family members who could be separated during earthquake
During - if indoors - DROP, COVER, and HOLD under a heavy piece of furniture positioned against the wall - step away from windows (shattering glass) and things that could fall on you - NO ELEVATOR
• If outdoors - stay away from buildings, street lights, utility lines

Question 51

earthquakes and plate tectonics

Answer 51

Earthquakes delineates plate boundaries - shallow focus on crest of oceanic ridge with transform faults btwn ridge segments - earthquakes at convergent plate margins occur in zone inclined downward beneath adjacent continent or island arc
—Find data on earthquakes and plate tectonics from seismic data centers (lots of them)

Global patterns of earth’s seismicity
—Locations and depths of historical earthquakes are recorded in seismicity maps - imp. Bc shows where and how the lithosphere of the earth is moving at present time

Question 52

divergent and transform plate boundariesand earthwakes

Answer 52

Divergent plate boundaries

• –Narrow belt of shallow focus earthquakes that coincides exactly with the oceanic ridge and marks boundaries btwn divergent plates
• –Shallow earthquakes along divergent plate boundaries are usually less than 15km deep and small in magnitude
• – Studies show that earthquakes associated with ridge crest are produced by normal faulting

Transform plate boundaries

• –Shallow focus earthquakes also follow transform faults - indicate horizontal (strike slip) displacement perpendicular to ridge crest
• –Earthquakes are restricted to active transform fault zone (Area btwn ridge axes) and do not occur in inactive fracture zones
• –Not all transform faults connect ocean ridge crests - many long transform faults connect convergent boundaries and others slice through continents
• –Most damaging transform faults occur on land - San Andreas fault

Question 53

subduction zones and earthquakes

Answer 53

Subduction zones

• —Most widespread and intense earthquake activity occurs along subduction zones at convergent plate boundaries where slabs of oceanic lithosphere dive down into the mantle
• –Strong concentration of shallow, intermediate and deep earthquakes along subduction zones in Pacific ocean
• –This zone produces the DEEPEST earthquakes
• ——-Great earthquakes of the last decade - Tohoku, Japan, and Sumatra, Indonesia were both megathrust earthquakes - where a plate of oceanic lithosphere is thrust beneath another at a subduction zone
• —— In 2004 Sumatran earthquake, shallow magnitude of 9.1 occurred on convergent plate boundary
• —–Sent a devastating tsunami W towards Indian ocean and E towards Thailand - more than 280,000 died

Question 54

collision zones and intraplate seismicity

Answer 54

Collision zones
—Himalayas define belt of shallow earthquakes - 2 continents collided here (India and Asia) - produced high mountain range but no deep earthquakes bc there is no longer a subduction zone

Intraplate seismicity

• –Although most of seismicity occurs along plate boundaries, continental platforms also experience infrequent and scattered shallow-focus earthquakes
• —Zones of seismicity in E Africa and W US - associated with incomplete rifting
• –Lateral motion of plate across asthenosphere involves slight vertical movement - built up stress can exceed strength of lithospheric plate, causing infrequent faulting and seismicity along old lines of weakness
• — Earthquakes can be large but infrequent

Question 55

seismic waves help us understand earth’s interior

Answer 55

• Waves passing through Earth are refracted in ways that show distinct discontinuities within earth’s interior and provide basis for belief that earth has a distinctive core
• Seismic waves create an “X-ray” of earth’s interior
○ Seismic waves - both P waves and S waves - travel faster through rigid material than through soft or plastic material - velocities of the waves give us an idea about the type of rock there - changes in wave velocities indicate changes in earth’s interior
• Both seismic and light waves have velocities that depend on the kind of material it passes through - if waves encounter a boundary btwn diff. substances, they are either reflected or refracted (bent)
• If earth were a homogenous solid, seismic waves would travel through it at a constant speed in all directions - a seismic wave (line perpendicular to the wave front) would then be a straight line
○ Tests showed that waves from far distance arrived at seismic stations sooner than was expected
○ The waves arriving at distant station travel deeper through earth than those reaching stations closer to the epicenter
§ If travel times of long-distance waves are shortened as they go deeper into earth, they must travel more rapidly at depth than they do near the surface
§ Led to conclusion that earth is not homogenous but made up of diff. physical properties that change with depth - seismic waves believed to bend and follow curved paths through earth
○ 1906, scientists recognized that whenever earthquake occurs, there is large region on opposite side where seismic waves are not detectable (take pic on pg 555!!)
§ Call this area the shadow zone - huge S wave shadow zone extends almost halfway around the earth, opposite the earth’s focus zone
□ Noticed that something stops the waves from traveling to opposite end - and bends them to go outwards - this was FIRST evidence that earth’s core was made of something diff. than rest of planet
□ S waves do NOT travel through the core!! Characteristic of S (Shear) waves is that they cannot travel through liquid - so proof that the outer core is liquid
® This combined with earth’s magnetic field and high density implied that the core was made of molten iron

Question 56

shadow zone and P waves

Answer 56

§ Shadow zone for P waves is more complex - forms a belt around the planet btwn 103 and 143 (take pic on 556) P waves are deflected but not completely stopped by the earth’s core - so not detected in shadow zone
□ The seismic waves traveling through mantle follow curved paths from focus and emerge at surface btwn 0 and 102 from focus (almost 25% around earth)
□ Refraction at boundary btwn core and mantle causes P wave of shadow zone
® More studies of the p wave shadow zone show that some weak P waves are received in this zone - this is evidence for solid inner core which deflects the deep, penetrating P waves

Question 57

seismic wave veolocity discontinuities

Answer 57

• Seismic discontinuities reveal the size of earth’s mantle, crust, and core - show how they have diff. chemical compositions
○ Also reveal info. About physical nature of interior, revealing a solid inner core, liquid outer core, and soft asthenosphere and rigid lithosphere
○ Seismic tomography is beg. To reveal a pattern of convection in the mantle
• Seismic discontinuities - minor variations in seismic velocities with depth - determined with recording stations - info. From seismic wave velocity vs. depth curves
○ First Moho discontinuity - reveals the continental crust is thicker than the oceanic crust
○ Most significant discontinuity is the low-velocity zone beneath the surface - trend for seismic wave velocities to inc. with depth in the mantle - however, in low velocity zone the trend is reversed and waves travel slower - proof that mantle is very near its melting points or partially molten, with 1-5% liquid
○ Most striking discontinuity occurs at core-mantle boundary - where S waves stop and velocities of P waves are drastically reduced - velocities of waves and density of outer core are explained if there is a change in composition and physical state - convincing evidence that earth’s core is made of iron
§ Deepest discontinuity is a strong inc. in seismic velocity - shows that the inner core is solid and more rigid than outer core

Question 58

convection inside earth

Answer 58

• Convection of core and mantle is most imp. Mechanism of heat transfer in Earth - convection in iron core probably creates the magnetic field, and convection in the mantle creates mantle plumes and plate tectonics
• Observations of 3D seismic tomographs have inc. understanding of convection of earth’s interior
• Convection in the core
○ Data shows core is made mostly of iron and divided by liquid outer core and solid inner core
○ Earth’s magnetic field probably forms by convection of the outer core, made of molten iron
○ Seismic studies suggest that the earth’s solid inner core spins a bit faster than the rest of the planet
• Convection in the mantle
○ Earth is dynamic also bc large-scale convection of its mantle
○ Changes in mineral assemblage and density of mantle may control the way the interior of the earth convects
○ One possibility is that upper mantle convects separately from lower mantle bc of diff. identified by seismic discontinuities - suggests mantle may convect in 2 more or less distinct layers that are usually separated
§ Lower mantle may convect by generating narrow cylindric plumes
○ Convection of upper mantle may be caused by cold slabs of slowly subducted lithosphere - the strong rock in lower mantle prevents it from penetrating…but as it builds up, could get enough weight to break through barrier into lower mantle

Question 59

wasatch fault

Answer 59

runs from border of Idaho and Utah down through Provo
—Comprised of 10 segments from Nephi to Brigham City
—On average, each segment has a major event every 1,200 - 1,500 years
—On average, a major event occurs every 300 years somewhere on the fault zone
Earthquake - vibration of the earth caused by rupture and sudden movement of rocks that have been strained beyond their ELASTIC LIMIT - when breaks the strain is released

Hypocenter (focus) = precise underground spot at which rocks begin to rupture or shift

Epicenter = point on surface of earth directly above the focus

Location and “Strength” of earthquakes are determined from evaluation of SEISMIC WAVES

Question 60

frequency of earthquakes (2-8)

Answer 60

Great - 8 or higher - 1 annually

Major - 7-7.9 - 32 ann.

Destructive - 6-6.9 - 120

Moderate - 5-5.9 - 800

Light - 4-4.9 - 6,200

Minor - 3-3.9 - 49,000

Very minor - 2-3 - 300,000

Question 61

locate earthquake

Answer 61

Know how fast S and P waves travel - can know time diff. btwn arrival of P and S waves at seismic station - then calc. how far away the focus is from the station
• Need 3 SEISMIC STATIONS TO LOCATE, or triangulate the focus of an earthquake
○ Bc even if you know how far away it is…you don’t know the direction

Question 62

earthquake damage and waves

Answer 62

1. Ground displacement
2. Ground motion
3. Ground failure/landslides
   ○ Landslide
   ○ Liquefaction - happened in Utah County
   § Mud volcanoes formed by liquefaction of sediments in Loma Prieta earthquake
4. Fire
   ○ San Fran earthquake 1906
5. Tsunamis
   ○ Honolulu earthquake caused massive tsunami

seismic waves

• –Waves are REFRACTED when they encounter changes in density and/or rigidity within the medium - wave changes its SPEED and sometimes its DIRECTION
• –If a wave encounters an abrupt change in the medium, it may be reflected if the angle of incidence is low

Question 63

24. earth’s resources

Answer 63

• Problem is not in finding more resources but in balancing resources among pop.
○ In early 1900s, pop. Was 1.7B now 7B+
○ Every 3 years, the equivalent of the pop. Of the current US is added to the earth
○ We now use more oil, gas, iron and other minerals than prev. used
○ Questions - find enough mineral deposits. Will oil be gone in 30 years, have enough agricultural lands, or enough water resources
§ One of most critical minerals is POTASH - name for water soluble potassium - the most imp. Fertilizer for agriculture - mining in S Utah

IMPORTANT
–The location and richness of most of earth’s natural resources are directly or indirectly controlled by plate tectonics

Question 64

Mineral resources

Answer 64

range from soils that support agriculture to metals like silicon, used in high tech. like computers
○ Tech. not minerals…oil, natural gas, coal and some other energy sources are included bc extracted from earth
○ Valuable minerals form slowly over long intervals of time under specific geologic conditions
○ Many cannot be replicated or found…however some metals, unlike fossil fuels, can be recycled
○ Very few minerals are renewable - or replenished in a short period of time - ex. Generation of oil from sedimentary rocks can take more than 10M years - so mineral deposits are exhaustible or nonrenewable
○ Mineral resources like a checking account - fast we withdraw, the sooner the account will be depleted - have made projections to determine how long mineral resources will be sufficient and lasting
• STUDY GRAPH ON PG.729

Question 65

4 processes that form minerals - 1.

Answer 65

Occurrence of mineral deposits is dependent on region’s specific geologic conditions and plate tectonic setting

1. igneous processes
   - -formed by magma - ultrmafic rocks host diamond - diamond bearing rocks by magma rise through deep mantle
   - -ores form when minerals forming in a magma have diff. temp. or crystallization and density
   - -magmatic segregation - process where dense mineral grains accumulate in layers near the base of an igneous body
   - -rare elements concentrating in last remaining melt…as they cool, the rate elements crystallize as minerals in a coarse-grained rock called pegmatite - indiv. Quartz crystals have formed in pegmatite
   - -hydrothermal fluid - hot water solutions of cooling magma concentrated with soluble materials - deposits known as hydrothermal ore deposits - form intrusions or veins

Question 66

4 processes that form minerals - 2.

Answer 66

2. Metamorphic processes - changes the texture and mineralogy of rocks to form imp. New mineral resources
   —Regional metamorphism - in roots of mountain belts
   ( Industrial minerals (graphite) - also marble and serpentine used to face buildings
   — Contact metam. - metamorphism along the contact btwn an igneous intrusion and the surrounding rock - heat and flow of chem. Active fluids from a cooling magma alter the adjacent rock by adding or removing elements (Limestone surrounding a granite pluton is susceptible to hydrothermal solutions related to intrusion
   —Seafloor metam. - hot hydrothermal fluids circulating through oceanic crust cause it

Question 67

4 processes that form minerals - 3.

Answer 67

3. Sedimentary processes
   - –Result of the erosion, transportation and deposition of sediments is the segregation of mineral grains according to size and density - soluble minerals transported in solution, silt and clay transported in suspension, and sand and gravel moved as bed load by strong currents
   - —–Clastic sediments - sand and gravel concentrated in rivers, beaches and alluvial fans - Used for construction and glass making industries - Originally form in veins, volcanic pipes and intrusions…minerals are eroded and transported by streams - bc denser, they are deposited
   - —-Chemical precipitates - come from seawater
   - ———–Also another way to concentrate minerals is evaporation of saline waters in restricted areas of ocean or large lakes where little clastic sediment is deposited
   - —- Sedimentary fluids - form in sedimentary basins as strata subside deeper and deeper levels in the crust - if meteoric water penetrates deep basins, heated up to 300C - with high temp. elements are extracted from rocks and crystalized out of fluid at shallower cooler levels

Question 68

4 processes that form minerals - 4.

Answer 68

4. weathering and groundwater processes
   - -Water removes soluble material like sodium, potassium, calcium and magnesium - weathering also enriches ore deposits
   - —- Ex. Gold occurs as small inclusions inside rock…weathering destroys the rock an leaves gold at surface
   - —-Chem. Weathering concentrates in regolith, an element that was dispersed throughout a rock body

Most imp. Resource formed by weathering is AGRICULTURAL SOIL - physical/chem. And biological activity imp. In soil formation - physical weathering breaks up rocks, chem. Weathering extracts minerals and produces new clay minerals - nutrients absorb into ground and clays absorb water so plants can use them
—Groundwater also - source of drinking and irrigation - aquifers is nonrenewable in soENme areas

Question 69

Energy resources

Answer 69

Modern society’s tech. progress and standard of living are related to energy consumption - limited
—Sources of energy found in renewable (solar, tidal, geothermal) and nonrenewable forms (minerals, coal, petroleum, fossil fuels)
• More than 90% of energy we use is produced from nonrenewable fossil fuels - too much consumption has led to energy crisis, which was predicted 60 years ago by Hubbert for Shell oil company - major oil crisis - consumption higher than production - leads to rises in oil prices bc supply is low
○ If poured all of the oil supply in Lake Superior in the Great Lakes, less than 5% of the lake’s volume would represent the word’s oil for all time - need to replace reliance on fossil fuels with other energy sources

Question 70

renewable energy sources

Answer 70

1. Solar energy - solar radiation is most imp. Renewable energy source - sun will cont. to shine for several B years
   - – Problem in solar energy being distributed over such a broad area - needs to be concentrated and distributed
   - –Photovoltaic cells - convert sunlight directly into electricity - calc. and outdoor lights are powered this way - also used for space satellites
   - –Limitations include # of sunny, cloud-free days in an area - or inefficiency of solar collectors
2. Hydroelectric power
   - –gravitational potential energy acquired by water is provided by the sun as it heats the ocean surface to produce water vapor - kinetic energy of water flowing downhill generates electricity - power plants built in dams or at waterfalls on rives
   - – Inexpensive and clean - dams also provide flood control and irrigation water
3. Wind energy
   - -Windmills - pump water - Denmark has goal to produce 50% of its energy this way - currently at 30%
   - –Advantages - it is pollution free, releases no carbon dioxide or greenhouse gases, req. no mining or fuel, no radiation dangers
   - -windmills are relatively expensive - sound pollution
4. Geothermal energy
   - –Earth’s internal source of heat - expressed in hot springs, geysers, and active volcanoes
   - –Temp. inc. with depth - but con bc most of earth’s heat is too far deep to be artificially tapped - heat we reach by drilling is too diffuse to be of economic value
   - —Advantages over others: nonpolluting - geothermal plants do not produce air pollution or CO2 like plants that burn oil and gas
   - –Renewable bc heat source is long-lived - large magma chamber takes thousands of years to cool
   - –Loses energy of it is prematurely extracted before fully replenished
5. Tidal energy
   —Ocean tidal energy harnessed by a dam built at the mouth of a bay where tidal range is high
   ○ At narrow entrance to bay, rise and fall of tides produce strong tidal current that can be channeled

Question 71

US Primary consumption

–reserves vs. resources

Answer 71

1. Petroleum - 37%
   
   2. Natural gas - 25%
   3. Coal - 21%
   4. Nuclear electric power - 9%
   5. Renewable energy - 8%

reserves - natural resources that have been discovered and can be exploited profitably with existing tech. and under prevailing economic conditions
–resources - deposits that we know or believe to exist, but are not exploitable today, whether for tech., economic, or political reasons

compare: world oil reserves are estimated at 700B barrels and world oil resources are around 2 T barrels

Question 72

petroleum oil formation

Answer 72

1. Remains of marine organisms collect on sea floor
   
   2. Partially decayed remains are buried under layers of sediment; kerogen forms in source rocks
   3. Kerogen is converted to hydrocarbons and migrated into reservoir rocks until trapped
   4. Oil and gas accumulate, trapped by impermeable cap rock at fault planes
      ○ Inc. time, temp. and pressure through all steps

oil consumption since 2000 - inc. most in China, Saudi Arabia, India - US consistent

Question 73

natural gas, oil shale, oil sand

Answer 73

Natural gas
• Advantages
○ Relatively clean, releases less CO2 than other fossil fuels
○ Reserves easily available for next 60+ years
• Disadvantages
○ Have to have pipelines to transport, so we are liable to have local shortages

Oil shale
• Has kerogen not converted to oil, so it can be heated to produce petroleum products
• Enough oil shale under US to supply ALL our energy for 5000 tears!
○ Problem - has to be mined and costs more

Oil sand
• Contains tar-like bitumen, which can be refined - could expand present oil reserves by 500% at present price
• Problem - must be mined

Question 74

coal - methane hydrate ices

Answer 74

Coal and peat
• Partially decomposed land plants in swamps near coasts and on floodplains
○ Bacteria, heat, and pressure remove other elements so it becomes more carbonized
• Advantages
○ There is a ton of it - to last more than 1500 years
○ Methane in coal beds can be exploited - more than natural gas
• Problems
○ Must be mined
○ Creates air pollution including greenhouse gases

Methane hydrate ices
• Form in deeper cold waters of ocean - contain 2x the C as oil, gas, and coal combined
• Volatile gas may be diff. to mine - is a greenhouse gas

Question 75

problems with fossil fuels

Answer 75

Problems with fossil fuels
• Acid rain
○ Sulfides in coal go into the atmosphere as smoke and ash, and react with water to form sulfuric acid
• Global warming
○ Fossil fuel burning produces CO2 and when builds up in atmosphere, heat from sun is trapped on earth’s surface more effectively

Question 76

nuclear energy

Answer 76

• Nuclear fission - U-235 atoms bombarded with neutrons - release energy and more neutrons - cause fission = “chain reaction”
• Controlling nuclear fission
○ To keep the chain reaction from causing an explosion, carbon control rods are inserted into the reactor core to absorb some of the neutrons generated
• Problems
○ Dwindling supply of U-235 or use breeder reactors - some poorly built reactors - don’t know what to do with nuclear waste produced
• Nuclear fusion
○ 2 nuclei must be smashed together to form a heavier nucleus - usually use 2 H atoms to form He - releases enormous amount of energy - usually takes enormous pressure and heat - not yet economically feasible

Question 77

25 other planets - origins of the solar system

Answer 77

Gravitational collapse of huge gas and dust cloud
○ Rotation around a central mass
○ Disk shaped cloud
○ Temp. variations segregated matter
○ Small particles accreted into large
Impact processes - imp. In formation and development of planets
○ Formation on moon may be from impact or glancing collision
○ Impact of Shoemaker-Levy 9 shows imp. Of these events

The solar system
○ Consists of the Sun, 8 planets, 1 planetoid (he still considers Pluto a planet), 61 known moons, asteroids, comets, etc.
§ All objects move in reg. orbit around sun
§ May be divided into three major groups - gas giants, inner planets, icy planets (Titan, Pluto)

Question 78

types of planets

Answer 78

1. Inner planets
   ○ Terrestrial planets
   ○ Mercury, Venus, Earth, Mars, Io
   ○ Small rocky planets of silicates and iron
   ○ Layered structure
   ○ Some have atmospheres of volatile gases
2. Outer planets
   ○ Uranus, Neptune
   ○ Large planets with low densities
   ○ We see tops of thick atmospheres
   ○ Likely have a rocky core similar to terrestrial planets
3. Icy planetary bodies
   ○ Pluto, comets and most moons of outer planets
   ○ Consist of ices of water, methane, ammonia, and nitrogen
   ○ May have silicate materials mixed with ice for a core

Question 79

the moon

Answer 79

○ Rocky body, less dense than Earth - lacks significant iron core
○ Lacks atmosphere and hydrosphere - erosion due only to impact craters - evidence of early history preserved
○ Impact processes are fundamental in planetary development
§ Impact craters have huge size range
§ Material is ejected
○ Lunar surface
§ 2 periods of formation
□ Older highlands are densely cratered
□ Younger Mare are flood basalts that smoothed surface

Question 80

Mercury

Answer 80

○ Small, high density planet with no atmosphere
○ 1,5x diameter of Moon
○ Density similar to earth - evidence for iron core
○ Old cratered surface, possible flood basalts - no evidence for tectonic activity

Question 81

mars

Answer 81

○ Similar to Earth in surface features - but half diameter
○ Generated more internal heat than Mercury or moon
§ Geo. Activity - shield volcanoes, deformation, evidence for liq. Water and atmosphere
○ Life on Mars
§ Meteorites from Martian surface contain evidence of microorganisms
§ Existence of life dependent on liquid water
§ Still question today if life exists

Question 82

Venus

Answer 82

○ Most like earth in size and density
§ Similar tectonic processes
§ Thick CO2 atmosphere with sulfuric acid clouds obscure view of surface
§ Not heavily cratered - still tectonic activity
○ Surface lacks significant depositional features - dominated by volcanic activity - tectonic features min. modified by erosion

Question 83

Jupiter

Answer 83

○ Jupiter and its moons form planetary system of their own - moon’s are solid planetary bodies
§ Io - innermost moon of Jupiter
□ Lacks ice, composed of silicates - slightly larger than our moon
□ Volcanically active - no crated surface - tidal forces may be source of energy
§ Europa
□ Composed mainly of silicate
□ Covered by frozen ice ocean - no craters, water lava eruptions, liquid water ocean may be beneath, sulfuric acid
§ Callisto
□ Jupiter’s outermost satellite - heavily cratered - water ice surrounding a rocky core
§ Ganymede
□ Largest moon - slightly larger than Mercury - smaller density - water ice surrounding rocky core
Jupiter has no known solid surface - density small, composed by H and helium

Question 84

Saturn

Answer 84

similar to Jupiter
○ Gas giant - numerous satellites - rings composed of icy particles - most of Saturn’s moons are tiny icy bodies
§ Titan
□ Larger than Mercury
□ Only moon in solar system with an atmosphere
§ Enceladus
□ Evidence for slushy lavas and ice tectonics

Question 85

Uranus

Answer 85

○ Similar in structure to Jupiter and Saturn - smaller, only about 4x Earth’s diameter
○ Atmosphere of methane
○ Thin ring system
○ Axis of rotation lies near plane of orbit - unique among planets
○ 5 major moons surround equator

Question 86

Neptune

Answer 86

○ Similar to Uranus but slightly smaller
○ Both thought to have ice and rock cores - methane in atmosphere - evidence for storms!!
○ Rings of icy particles - thin atmosphere
○ Largest moon Triton

Question 87

Pluto

Answer 87

○ Furthest, smallest, coldest, darkest
		○ 250 yr. orbit
		○ Lacks thick H-He atmosphere of other outer planets (similar to Neptune's moons)
		○ Surface is frozen nitrogen
		○ Has one moon - Charon

Question 88

Sedna

Answer 88

○ New most distant known object in solar system - announced by NASA - twice distance to Pluto, is near its closest approach to the Sun
○ Estimated to be 3/4 the size of Pluto
Ellipse orbit

Question 89

Comets

Answer 89

○ Small bodies composed of ice and dust
○ Tail formed by vaporization of ices
○ Some have huge orbits (10s of 1000s of years for 1 rotation)
○ Orbital paths are complex
• 50,000 yrs. Ago - huge iron-nickel meteorite struck N AZ - left large crater