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/ Calculus, math / CAL 105 / What is the meaning of tensile fractures in rock deformation?

What is the meaning of tensile fractures in rock deformation?

What is the meaning of tensile fractures in rock deformation?

Description

School: 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months
Department: Calculus, math
Course: Planet Earth
Professor: John platt
Term: Fall 2016
Tags: planet and EARTH
Cost: 25
Name: Planet Earth post midterm
Description: Week 7 notes, going into the origin of the Earth
Uploaded: 10/07/2016
12 Pages 245 Views 3 Unlocks
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9/30  


What is the meaning of tensile fractures in rock deformation?



Rock Deformation :  

 - Rock Fractures

 - tensile fractures open out  

 - shear fractures slip along the fracture surface  

 - natural faults are a type of shear fracture  

Structures in zones of continental rifting  

Normal fault: the top side slips down relative to the bottom side  

- A normal fault occurs when the crust is extended 

- Hanging wall has moved down relative to the footwall


What is the meaning of shear fractures in rock deformation?



-

Graben structure:  

- A valley which is defined by two normal faults (horsts), inclined in opposite directions.  

Structures in zones of plate convergence :  

- Tibet, area of shortening and thickening of continental crust

- 3

Reverse fault: the top side slips up, relative to the bottom side  If you want to learn more check out What is the rate of change of temperature with height called?


What is the meaning of tectonic associations of faults?



A thrust is a low-angle reverse fault  

- Glarus Thrust, Central Alps

Transform zones  

- Strike-slip faults, slip horizontally parallel to fault surface

- San Andreas fault  

- Right-slip fault, when crossing the fault, have to go down to your right to find the  fault

----------------------------------------------------------------------------------------------------------------------------  Week 7 :  

10/3

Rock Deformation II cont’d  

Retaining and releasing bends  

- A bend to the right on a right-slip fault is a releasing bend, this may produce a basin - A bend to the left on a right-slip fault is a restraining bend, this may produce uplift and  mountains  If you want to learn more check out How is culture transmitted through enculturation?

( example : Salton sea pull-apart basin along San Andreas Fault)  

- San Andreas fault unique because of its “Big Bend”

- Restraining bends cause overlap of the crust, creating mountains

Tectonic associations of faults: Summary:

- Normal faults are most common in right zones

- Thrust faults are common in zones of plate convergence

- Strike-slip faults are dominant in transform zones  Don't forget about the age old question of What is equality of opportunity in sociology?

Fault Rocks:  

- Faults contain zones a few mm to a km wide of fault rock

- Fault rocks are produced by mechanical and chemical breakdown of the rocks on either  side of the fault

- Fault breccia: produced by mechanical fragmentation dominant Don't forget about the age old question of What does positive strain mean?

- Fault gouge: chemical alteration to clay - Mylonite : Ductile deformation

Folds:  

- Bedded strata may be tilted and folded by forces associated with plate motion  • Attitude of bedding – strike and dip

Strike and dip

- The strike is the orientation of the horizontal line in the plane of bedding - The dip is the inclination of the bedding from the horizontal - The direction of dip is perpendicular to the strike and must be specific  Don't forget about the age old question of What is the meaning of ethnocentrism in anthropology?

- An anticline is afold that closes upwards

- The oldest rocks are in the core of the fold - A syncline is a fold that closes downwards

- The youngest rocks are in the core of the fold  

Structures and maps :

- A geological map is a direct representation of the geology seen on the Earth’s surfaceWe also discuss several other topics like What is the meaning of conditional proofs?

10/5

Origin of the Earth and the Solar System:

Stages in the formation of the solar system:

1. Formation of solar nebula and protostar

2. Accretion of planetesimals

3. Formation of planets

- Processes started 4560 million years ago, and took a few tens of millions of years to  complete.

Eagle Nebula :  

- Cloud of gas and dust like these are the birthplace of stars  

- very big and dilute

- Would not be able to distinguish space from a vacuum

- Visible through telescope

- “Black yama”

- Suppression of gas and dust creates Eagle Nebula, starts to contract under its own  gravity and start a new star or several

 - gravitational collapse is first step of creating a star  

 1. Collapsing cloud

 - a diffuse, roughly spherical, slowly rotating nebula begins to contract   - As contact, start to spin, “concentration of angular momentum” (like a figure  skater)  

 - gas clouds contracting hundreds to thousands of times  

 - centrifugal force, shorthand way of expressing when something rotates, in order  to keep it together have to pull in ( flying away from the force)  

 

 2. Formation of solar nebula

 - Stars and planetary systems form by collapse of interstellar clouds under  gravity  

 - Clouds collapse into a disk  

 - central part of disk collapses to form a protostar

 - hot, fairly high density ball of gas in the middle  

 3. Accretion of planetesimals

 - planetesimals- little, proto planets  

 - grands of rock dust, minerals and ices accreted to form km-sized bodies   - gas getting more concentrated as result of collapse of the cloud   - first, form dirty snow. Bits of dust and ice stick to each other   - dirty snow flakes turn into dirty snowballs, they grow bigger until  becoming big enough to regard as celestial object  

 - Planetesimal.  

 4. Formation of planets

 - start of nuclear fusion in proto-star generates solar wind- strips gas from inner  solar system  

 - planetesimals accrete to form terrestrial planets in the inner solar system   - gas giants grow around larger planetesimals in outer solar system   - * know about inner planets- Venus, Earth, Mercury, Mars   * outer planets - Jupiter, Saturn, Uranus, Neptune, Pluto   - asteroid belt between jupiter and inner planets  

 - Jupiter’s gravity stops asteroid belt substances from becoming planets   - collisions of planetesimals form creations of planets  

 - larger objects pull in more and more material, gas, and planetesimals   -while planets were developing, sun developed from a proto-star.   - nuclear fusion produces massive amounts of energy   - gas in outer part of the solar system was able to form the gas giants   ^one big problem with this theory of creation of planets   - most gas giant planets found around other stars are very close to  their parent stars  

Terrestrial (rocky) planets

- Mercury, Venus, Earth- Moon System

- Venus

- Earth-Moon system

- Mars

- Several of the moons of Jupiter and Saturn and some of the asteroids are comparable in  size composition and structure to the terrestrial planets

Venus :  

- Sister planet , remarkably similar in size and composition to Earth

- Very weak magnetic field

- No plate tectonics

- Curious why different from Earth in this way

- Extensive volcanic activity ( but no plate tectonic so mostly mantle plume, more vigorous  convection in the mantle)

- Cryptic tectonic structures

 - “arachnoid” because looks like spider webb  

 

- Very thick, hot atmosphere

- No oceans ( completely dry)

Landforms on Venus

- Tesserae

- Corona  

- Do not know how these things were formed

Mars :  

- About half the diameter of Earth

- No magnetic field- solid core?

- No plate tectonics

- Active volcanic and tectonic activity during first billion years

- Mantle plumes probably most common volcanic process on the planets - Very thin, cold atmosphere

- No surface water, but there may have been in the past

- Some features look like once frozen glaciers

- Alluvial channels on Mars look like once stream channels

- Valle Marineris : 5 km deep , largest feature on mars, many times deeper than the Grand  Canyon  

-

Saturn :  

- Titan is Saturn’s biggest moon

- Saturn’s rings massive compared to its rings, but Titan could be responsible for  movement of the rings

- Titan  

- Larger than the planet Mercury

- Rocky core, water mantle, thick ice crust

- Nitrogen atmosphere  

- Lakes of methane, rains methane, snows methane

10/7  

The Early Earth:

Origin of the Earth-Moon system

- Earth’s moon unique in that it is a significant fraction of the size of the Earth - Composition of the Moon is very similar to the Earth’s mantle

- Theories for the origin of the Moon  

- Capture  

- Moon was formed as separate, mini planet and captured by the orbit of  the Earth

- Fission  

- Moon formed out of part of the Earth and thrust into space

- Formation together w/ the Earth in the same orbit

- Formed together as separate objects in the same orbit from the start

- Interplanetary collision  

- Formed out of interplanetary catastrophe  

 ^ most of these not possible or improbable.  

 - Capture : not possible unless two objects touch each other   - Fissure: no way Earth could spin so rapidly to throw the moon off.   - Formation W/ Earth: possible, but then why is the moon so much larger   comparison to the Earth compared to other planets and their moons.

- Interplanetary Collision: Most likely  

 - Mars sized body impacted Earth  

 - giant impact propelled shower of debris into space   - Earth reformed as largely as molten body and moon   aggregated from debris  

 - impact sped up Earth’s rotation and tilted Earth’s orbital  plane 23 degrees.  

- Moon pushed further and further away by time and forces  

 

 

- Moon/ Earth 1:81 Titan/Jupiter 1:20,000 (<-- Size)

- Composition of the moon very similar of composition of Earth’s mantle - Moon does not have core, ball of rock, close relationship to the Earth - Moon always presents the same face to the Earth, always seen the same side of  the moon ( before Apollo, had never seen backside of the moon)

The First Crust:

 

- After formation of the moon, the Earth’s mantle may have been largely molten - An early crust may have formed on magma ocean, made of anorthosite: not now  preserved (composed almost entirely of plagioclase)

- Early anorthosite crust on the moon still there: 4.5 billion years old - Earth’s early crust was continuously destroyed and recycled by mantle  convection and asteroid impacts

- Earth’s moon a clue to the nature of the early Earth:  

- The lunar highlands are made of anorthosite

- Lunar mare are floored by basalt

- Lunar surface is dominated by impacts

- Euler crater: probably formed as result of relatively small object. When  impacting body hits surface of a planet, hits and evaporates, instantly  creating crater

- Central Peak, after hugs mass of hot material is ejected leaves  central peak.  

- Mare Orientalis: a multi-ring impact basin ( on other side of the moon)

- Result of bringing sizable object in and hits the moon, produces  

700 km crater. Rings are effects of progressive collapse into lunar  

hole ( a few hundred kilometers deep)

- Mare are themselves impact basins  

 - Lunar “seas” were formed as giant impact structures before 3.9 Ga (gigayears),   later filled by flood basalt. Similar impacts must have occurred on Earth.   - Because Earth so close to moon during all   this violent collision, impact events.  

 - Many early impactors may have been comets, which supplied Earth with water   and organic compound; may be formed Earth’s oceans and atmosphere

The Early Earth:

 

- Heavy Bombardment by asteroids and comets during first few hundred million years - Rapid convective overturn of mantle continuously recycled the primitive crust - Early was 20% less bright than at present ( meaning ice age)

- Early atmosphere rich in N2, C02, Possibly CH4

- Early oceans hot, acidic

- No life, and hence no oxygen

- Oxygen almost 100% due to photosynthesis

- Remember Eons and Sequence by which they occur

Hadean Eon:  

- 4560-3900 Ma: Origin of Earth to first preserved crustal rocks

- Heavy bombardment by asteroids and comets during first few hundred million years - Rapid convective overturn of mantle

- Early sun 20% less bright

- Atmosphere rich in N2, C02, CH4

- Early oceans hot, acidic

- No Oxygen

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