geo exam 1

subduction zones were discovered when

it was noticed that deep earthquakes are found only near ocean trenches, and that earthquakes increase in depth with distance from trench-only one one side (earthquakes are concentrated on plate boundaries, deep earthquakes=ocean trench, earthqakes mark subduction-EARTHQUAKES AND TRENCH RELATIONSHIP-bc normally earthquakes aren't possible in asthenosphere)

tectonic plates of ridgid and brittle lithosphere move over a softer and ductile asthenosphere below

:)

the division of earths interior to mantle/core/crust is used to describe differences in

composition (chemical, physical, behavior)-solid/liquid, how it deforms-->melting point: below (regid+solid), close (soft solid), above (liquid-rare)

-core: mantle warmer, iron
-crust: lighter silicates
-mantle: iron magnesium silicates

what is the relationship between the crust and lithosphere

lithosphere includes both crust+upper mantle (chemical properties of crust+mantle)

how did earths formation make plates possible

-large amounts of heat
-melted as formed which made layers by densities
-heat left from formation means convenction creates motions

crust vs mantle

-crust has more light silicas
(Na, K vs heavy/mantle Fe, Mg)

magnetic patterns in rocks making up the oceanic crust appear as

bands of normal and reversed magnetization parallel to the oceanic ridge

oceanic crust is youngest at ridge and gets older with increasing distance away from ridge

:)

when 2 oceanic plates collide

the older subducts

location+ages of Hawaii islands shows

rate+movement of pacific plate

geologic evidence that led to discovery of seafloor spreading

new material being pushed out, old rock farther from ridge, magnetic patters allowed for tracking

geologic evidence that led to discovery of subduction

earthquakes during subduction, strength of earthquake nearer or farther away, volcanoes formed

cleavage

minerals breaking where bonding between atoms is weak

ice is a mineral

:)

accreted terrains are added by

subduction

at a passive continental margin the prime geologic process occuring is

sedimentation (thin crust makes a shelf for sediment to gather on)

solid solution

subsitutuion/proportions

costal ranges formed by

accreation of buoyant material onto overriding plate

cascades formed by

magma intrusion+volcanism above subduction plate

why are silicate minerals so common in crust

most common elements are O and silicon

oxide example:

hematite

biotite vs muscovite

biotite (sheet silicate with excellent cleavage in one direction?) has 2 cleavage directions, muscovite has 1

which mineral is hardest

:)

tectonic cycle

-rift breaks apart continent
-new divergent/ridge forms
-ocean basin forms
-subduction as older (closes again, not wider)
-terranes accreted to continent
-continents collide when oceanic crust completely subducted

red sea, pangea, mountains of west coast/coastal range

Planetary accretion

gravitational attraction+collision between smaller fragments-produced planets (shooting star, kinetic engery converted on impact into heat, resulted in melting of earth/more mobile in liquid state)

Earth’s internal structure: layers of different composition; layers of different physical properties – be able to use and explain both sets of terminology

-lithosphere (crust+upper mantle, cool+rigid+strong but breakable)
-asthenosphere (upper mantle, warmer+soft+flowable, close to melting point-where convection occurs)
-mesophere (lower mantle, high melting point bc high pressure+strong)
-outer core (liquid)
-inner core (solid)

-physical state+behavior: determined by proximity to melting point, controlled by temp+pressure+composition
-below melting point: rigid, solid, brittle
-close to melting point: soft solid
-above melting point: liquid, lacks strength
(core, mantle, crust)

Tectonic setting of the Pacific Northwest and the plates involved.

-pacific plate: ocean
-juan de fuca plate: small, in ocean off coast, will cause big one?
-north american plate

-an active plate boundary, specifically an ocean-continent convergent plate boundary with a subduction zone.

subatomic particles and the structure of the atom, isotopes, ions, types of bonding.

-ions: change number of electrons (cation: lose, anion: gain)
-isotopes: The atoms belonging to the same element, having same atomic number Z, but different mass number A
-bonding: ionic (negative+positive attract and stick), covalent (sharing an electron rather than transfer), metallic (middle periodic table, share electron with multiple, conducts electricity)

families of silicate minerals with examples of minerals from each group

-isolated: olivine (not linked)
-single chain: pyroxene
-double chain: amphibole
-sheet: muscovite
-network: quartz

Describe the earth’s structure, in terms of both chemical composition and physical properties.

iron, oxygen, silicon, magnesium, ect.

oceanic crust, continental crust, plates?

How does accretion and differentiation make plate tectonics possible?

layers?

what causes plates to move

convection in ductile asthenospher (heat)

-accreation+radioactivite decay make heat

What is the scientific method?

observe, hypothesis, {predict, test, modify hypothesis}

Explain the geologic evidence for continental drift

-Fit of coastlines
-Distribution of fossils
-Similar types/ages of
rocks on widely
separated coastlines
(land bridges, PANGEA, separation rate, lateral)

Why does Earth have a magnetic field?

The Earth's magnetic field is believed to be generated by electric currents in the conductive material of its core, created by convection currents due to heat escaping from the core.

(On Earth, flowing of liquid metal in the outer core of the planet generates electric currents. The rotation of Earth on its axis causes these electric currents to form a magnetic field which extends around the planet.)

What are hotspots

plume of hot rock rising from deep mantle

planetary differentiation

molten earth segregated into layers by density (dense: iron+nickle-sank to form core, light: si+o+ect-rose to form crust, mantle-middle)

What is the difference between a hypothesis and a scientific theory?

theory: hypothesises repeating (testing)
hypothesis: proposed explanation made on the basis of limited evidence as a starting point for further investigation.

How do rocks provide a record of the magnetic field back through time?

polarity locked in as rock cools, iron minerals, polarity made by rotation+molten iron in outer core (normal vs reverse)

How do magnetic reversals provide evidence of seafloor spreading?

reversed: N near south pole, rare? (When the Earth's magnetic field reverses, a new stripe, with the new polarity, begins.

When the Earth's magnetic field reverses, the magnetized minerals align in the opposite direction. The record of magnetic reversals is carried away from each side of the spreading center of a mid-ocean ridge, showing that the molten rock is creating new lithosphere.)

Explain the geologic evidence for sea floor spreading

rocks progressively older away from RIDGES, no old oceanic crust (changes in magnetic field recorded in ocean crust)

Explain the geologic evidence for subduction.

subduction: how oceanic crust is removed

deep earthquakes near trenches+volcanoes (deeper away from trench), cold rock pushed away from ridge into/down into? mantle

How does plate tectonics explain continental drift, seafloor spreading, subduction?

continental drift (the movement of continents resulting from the motion of tectonic plates, lateral-fit of coastlines)
seafloor spreading (plates splitting apart from each other, new material pushed out, magnetic patterns=tracking)
subduction(how oceanic crust is removed, earthquakes+volcanoes)

conveyor belt

plates move creating splits/moving earth??

what can hot spots tell us about plate movement?

magma pushes up from deep Earth to form volcanoes—and can be used to determine how fast tectonic plates move, plates move above the hot spot (divergent or convergent+hotspot track: chain of progressively older volcanoes)

example of divergent boundary

The Mid-Atlantic Ridge

example of convergent boundary

The Pacific Ring of Fire

example of transform boundary

The San Andreas Fault

geologic process that occur at divergent

earthquakes, volcanoes, moving apart (new oceanic crust from magma, ridges, magma goes to the top of asthenosphere, sea floor spreads)

geologic process that occur at convergent

earthquakes, volcanoes, moving together (crust sinks, water is added, magma then floats and creates island arc)

geologic process that occur at transform

faulting+earthquakes, moving side by side

Describe the process of continental rifting

tensional stress & buoyant uplifting of the heated lithosphere cause the upper crust to be broken along normal faults, while the lower crust deforms by ductile stretching

Contrast the geologic processes features occurring along active and passive continental margins

-Active continental margins tend to have narrow continental shelves+The west coast of the United States is an example of an active margin, where the coastline corresponds with the boundary between the Pacific and North America Plates.
-Passive continental margins are continental margins that are not tectonically active. These areas have flat lands and have a wide continental shelf, which is the submerged border of the continent. A passive continental margin occurs where the transition from land to sea is not associated with a plate boundary.

What is a tectonic setting?

geologic location relative ot nearby plate boundaries/hotspot/types

Use the periodic table and the concept of valence electrons to explain the importance of silicon as a building block in many types of minerals.

-tetrahedron (structure+subsitution+bonds)
-ionic radii (sharing electrons/substituion)
-4 valence electrons
-mineral compound

What is a mineral?

naturally occuring (in-organic, solid) combination of specific elements (proportions/range) arrangeged in a particular repeating 3-d structure

color

unreliable, reflects composition

Describe the different ways silicate ions can be joined together to form silicate minerals. Give examples.

-sheet, double chains, framework, single chain, rings, pairs, isolated

Explain the physical properties you would use to distinguish between common minerals such as calcite and halite, graphite and galena, pyroxene and amphibole, talc and mica, etc.

-calcite+halite: shape, color/luster
-graphite+galena: lustre, streaks
-pyroxene+amphibole:
-talc+mica:

Describe the composition of the mantle and crust and the minerals that are commonly found there.

-mantle: peridotite (45% SiO2)
-continental crust:granite (60-75% SiO2)

Describe the process of continental collision

-mountains form

major tectonic features associated with continental collision

-Olympics/ Coast Ranges: accretion,
compression
• Cascades/Sierra Nevada: arc
volcanism, intrusion
• Northern Rockies: platform
compressed, folded, thrust faulted
• Southern Rockies: “basement” (craton)
compressed and squeezed upward
• Basin and Range: divergent forces -
crust stretched and thinned while
heated by upwelling mantle

major tectonic features associated with continental rifting

ridge, abyssal plain, continental slope, continental shelf

Describe the tectonic setting of the Pacific Northwest, including the differences between the Coast Range and the Cascades.

-olympic/coast ranges: accretion+compression
-cascades:arc volcanism, intrusion

Are minerals that show solid solution different types of minerals? How about minerals that show polymorphism? Explain your answers.

-solid solution: elements can be present in any proportion [(Fe,Mg)2SiO4, homogeneous solutions]
-polymorphs: same chemical composition but different crystal structure (diamond vs graphite, both carbon just different pressure--A polymorph is a mineral with the same chemical composition but a different internal structure)

streak

more relaible color sample (grind in streak/powder)

luster

way light reflects+degree it penetrates into interior (edges), reliable (metalic vs nonmetallic)

hardness

resistance to stracting (will be scratched by every mineral whith higher hardness, mohs/common objects)

habit

cubic, etc (number words)

cleavage+fracture

-cleavage: three directions of cleavage, 90˚ (grain/layers, SPECIFIC BREAK)
-fracture: irregular break

density

mass ;)

other

solubility, magnetic, taste, smell, ect

identification properties

color, streak, lustre, hardness, habit, cleavage/fracture, density, other

oxides

O^-2 anion
-hematite, magnetite (hydroxides: limonite, bauxite)

sulphites

S^-2 anion
-galena, pyrite, chalcopyrite

sulphates

SO^-4 anion
-anhydrite, gypsum

halides

halogen element anions (chlorine, fluorine, bromine, etc.)
-halite, fluorite

carbonates

CO3^-2 anion
-calcite, dolomite, azurite

phosphate

PO4^-3 anion
-apatite

silicate

silicon, oxygen in various proportions
-olivine, feldspar, quartz

native minerals

single-element minerals
-gold, copper, sulphur

mineral groups

oxides, sulphides, sulphates, halides, carbonates, phosphate, silicate, native minerals

Discovery of plate tectonics: (what they are and how they were discovered)

early plate motion evidence:
-contintnetal dirft, seafloor spreading, subduction
-no old oceanic crust
-volcanoes, earthquakes
-magentism
-fossils/rocks

plate tectonic: circulation of solid earth, result of how earth formed

rifting/wilson cycle

-heat
-crust stretches+things
-oceanic crust forms between separating continents (narrow sea)
-widens by seafloor spreading (passive margins)

How are different processes recorded in different rock types?

-sedimentary, igneous, and metamorphic
- physical changes—such as melting, cooling, eroding, compacting, or deforming
(rock cycle)

Distinguishing properties of important minerals from the lab: quartz, feldspar, micas, olivine; or minerals that might be confused with each other: i.e., halite vs. calcite, graphite vs. galena

-calcite+halite: shape, color/luster
-graphite+galena: lustre, streaks
-pyroxene+amphibole:
-talc+mica:

cratons

very old, highly differentiated crust (silica rich)

orogenic belts

deformed+metamorphosed rocks

accreatred terranes

the blocks of continental fragments and oceanic islands that have collided with a continent and are now permanently attached

how is continental crust made

-subduction zone (separate by density, add instead of sinking)
-accreation of buoyant material as oceanic crust subducts (builds cont. outward)
-terrrane: block of crust with different geologic origin+history from adjacent areas
-melting of subducted plate+mantle (adds silica)---->erupts on surface or emplaced within crust intrusions

structure of oceanic crust

-marine sediment (top)
-pillow basalts
-dykes (fissures lava erupted through onto coean floor-later filled with basalt)
-gabbro (intrusive fake basalt)
-peridotite: (Fe/Mg rich mantle rock

passive margin

transition between oceanic+continental crust, not on active plate boundary (rifted_thin cont. crust)

tectonic features of ocean basins

seafloor spreading, subduciton?

ridge, abyssal plain, cont slope+shelf

rock cycle

-magma
(cooling)
-intrusive/extrusive igneous
uplift)
-outcrop
(weathering, etc)
-sediment
(buried, compact)
-sedimentary rock
(deeper bury, heat, pressure)
-metamorphic rock
(melting)

driven by internal heat

decompression melting

moved toward surface (mantle plume/convection cell)

flux melting

water

bowen reaction series

composiiton+stage of melting

fractional crystallization

magma compisition changes as crystals form/cool/sink?

igneous

cooling+crystal (magma)

metamorphic

re-crystalize at high temp/pressure without melting

basalt

-high Fe, Mg, Ca, low Na+K
-mafic
-45-55% silica
-low viscosity (thinner crust)
-mafic igneous rock with an effusive texture