EOS 120 Mid-Final
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What is a mineral? Or qualities that minerals have? (5 things)
- * great majority inorganicly derived
- *naturally occuring
- *have a distinct internal structure (bond lattice)
- *maintain a fixed chemical composition
- *homogenous mixture
Is salt a mineral?
its fits all the criteria, its main difference from sugar is that it is inorganic.
Is sugar a mineral?
It breaks a couple of the rules. it is organic, and it must be produced/synthesized (nbot natuarlly occuring)
Is water a mineral?
In general NO....some may answer that in its solid form ice it could be considered so.
are crystalls minerals?
some are some arent. they must fit the criteria....mostly due to naturally occuring
in some minerals ions w/ simialar charge and radius may be substituted for one another.
- ex. feldspare (NaAlSi3O8) subs the Na+ for K+ Quartz SiO2 is very pure because the Si & O are not easily substituted.
ions try to fill their valence shells to gain stability
covelaent = sharing=strong
# of minerals in the crust?
what are the most common rock forming minerals?
only about 20 minerals that make up earths crust.
most common are silicates made of Si & O
remainder are Al,Mg,Na,K, Fe
Mineral Stability Changes
minerals become unstable with changes in heat and pressure.
In a subduction zone hydrous minerals sink with the crust
pressure becomes to great
they become unstable and form new minerals a/o rocks
- plagioclase----------> pyroxene/garnet
Gr4aphite to diamond
due to mineral stability relating to pressure graphite turns to diamond
pressure only found below 140km deep
so how do diamonds exist on surface? surface conditions are not enough to break the covelant bonds.
4 main products of weathering
- 1. rounded structures
- 2. losse debris (regolith)
- 3. secondary minerals (ions in solution)
- 4. creating landforms
3 types of weathering
- Physical - mechanical breakage
- no change in chemistry
- **increases surface area
- Chemical - decomposition
- weakening of chemical bonds
- reactions work to 'stabalize' minerals
-combo roots wedge and also produce hemic acid
- **often work together
- **water usually required
2 mian procces of physical weathering
1. ice wedging - water in craks freezes-->expands=broken rock
2.pressure unloading- rock formed at high heat pressure relaxs at surface and breaks along prefered orientation
3 main factors of chemical weathering
1. dissolution - everything disolved no by product (halite/calcite)
2. hydrolosis - clay minerals left behind (feldspare to claymineral-kaolinite and disolved minerals)
3. oxidations -with atmospheric or hydrous oxygen (iron oxides)
Sedimentary Rock Types (3)
Clastic - made of other rocks (brecia, conglomerate, sand stone, mud stone etc.)
Chemical - evaporites (rock salt)
Biological - from plants/animals (coal)
What is mass wasting?
- *downslope movement of earth materials
- * when driving force (down slope) > resisting (retaining) force
* either slope increases OR cohesion(friction) decreases
- material strenght - weathering = less cohesion (strenght)
- weathering = more mass=more force
over steepening -
- water content - high = additional mass = more force
- high= less cohesion= less resistence
i.e. undercutting - a slope will try to achieve equilibrium
5 types of mass wasting
Creep - gradual down slope movement - very slow
Slump - movement of a choherent mass along a curve - slow to moderate
Flows - material is in a viscous flowing state, mudflows earth flows & debris flows - rapid movement
slides - total failure along a determined plain (slipage plain) - rapid to moderate
falls - material movement through the air
how does human activity effect mass wasting?
1. creation of new or altered landscapes
2. alteration of procesess.
however rivers are the single biggest factor to errosion!
How do fluvial systems transport sediment? (5)
- 1. stream competence - ability to transport sediments by size/density
- 2. Stream capacity - ability to transport volume of sediment
- 3. suspeneded load - fine sediment in suspension (clays etc)
- 4. bedload - rolling sliding coarse particle
- 5. dissolution - disolved sediments
Flooding - talk about that shit
- * most frequent of all natural disaters
- *when Q/driving force/shearstress exceeds channel capacity
- recurence i.e. 100yr flood is not how often but how likelky i.e. a probability
- *100yr flood = 1% chance, 2year flood = 50%
- *it is encouraged by human activity
- paved surface= less ground saturation=more run off
- bridges restrict river flow
- changing the base level and slope of profiles
ground water - what the fuck is it?
- water in pore spaces in the ground
- percalation zone = water travels throuhgh
- saturation zone = all pores are 'full'
the line between the two is the water table - it generally follows the topography.
recycletime= residencetime/rate of exchange (~280 yrs)
how can one date ground water?
by H isotopes in the water
- H1 most common
- H3 or trintium is radioactive
porosity vs permiabliity
- porosity = % volume of por space in sediment
- common soil is 30-50%
permiability= ability of water to move through substrate determined by pore size (not pore %)
aquitards vs aquifers
aquifers = permiable regions transmit water freely (san, gravel)
aquitards = impermiable layers that hinder prevent mobility (clay)
what is a cone of depression?
excessive use of ground water lowers the localized water table and can leave neighbooring wells dry.
ireversible loss of aquifers
reduced structure of soils (leaning tower piza)
contamination , leaching through permiable layers into ground water
glaciers hold________ percentage of water & __________percentage of fresh water
they hold about 3% of total water and 95%of fresh water
formation of glacial ice (4 steps)
- snowflake--->granular snow-------->firm---------->glacial ice
- lose struc. packing formation
how do glaceicers move? (3 items)
they flow under their own weight in an almost plastic like way
creep - rotating grains underneath act as rollers
basal slip - water lubricant underneath
points on the outside have more drag the in the middle so the middle moves downslope faster
two types of glaciers
1. valley glaciecer - like frozen rivers
2. ice sheets - huge regardless of topography
what is till?
the result of glacial errosion and transportation. a poorly sorted mixture of shit
land forms rivers vs glacial
- rounded peaks, overlaping spurs, V shapped valleys
- horns(sharp peaks) cirques, morains
- after glaciation
- horns, truncated spurs, hanging valleys, U shapped valleys
types of moraines (4)
- lateral - along sides
- medial - down the middle -when two ice flows come together
- terminal - marks the furthest advance
- recesional- built as the glacier receeds.
Ice ages requirements
caused by malakovitch cycles
- 1. earths orbit is eccentric (sometimes closer or further from sun)
- 2.obliquity or axis tilt ( which parts of earth face the sun at what angle)
- 3.percision or the wooble on the obliquity
- cool planet - thus eccentric orbit
- percipitation - high seasonability due to high obliguity
how are clastic sedimentary rocks formed (4 steps)
- 1.weathering and eroision creates detritus
- 2. detritus transported to basin
- 3. deposition of detritus in basin
- 4. lithifacation
what are terrigenous sediments and turbidity currents?
terrigenous sediments are sediments eroded on land and transported to sea by rivers,
turbidity current is like an underwater river, water more dense from above sediments moves downward
these two factors create the continetal shelf
how does compaction cementation work?
as a pile of sediments grows, pressure forces water out of and compacts the pore space, minerals percipitate out of the water and creates cements
comon cements are carbonates, clays, silica
what is an attol? how formed?
a reef island in the middle of the ocean
a reef grows alongside a hotspot volcano, as the plate moves the volcano cools and supsides, reef continues to grow upward
deep sea chemical sediments (2)
- created from > 30% biogenic material
- calcareous ouze - Ca rich
- silicieous ouze SiO2 rich
depesiotional history of shorelines
- transgression - sea moves onto land
- regression - the opposite
sediments and deposition occur in different locations (finer sediment further from shore line) therefore we can see a 'barcode' of the changing sea level by overlying layers of sand and clay
from oldest to youngest eons (3)
a-pro-phan = archean , proterozoic, phanerozoic
- archean = 3800-2500 mya
- proterozoic = 2500-570mya
- phanerozoic = 570mya - pres
earth’s oldest minerals
Zircon grains from metamorphosed sediments U-Pb radiometric ages 4.4 billion years old
- Age of Solar System 4.567 Ga
- • Oldest detrital zircons ~ 4.4 Ga Western Australia: implication of oceans
- • Oldest Rocks 4 Ga, Acasta Gneisses, NWT Canada
- • Oldest Supracrustal volcanics and seds 3.8 Ga, Isua, Greenland
- • Oldest well preserved terrane, fossils 3.5 Ga, W. Australia
proof of early water on earth?
pillow lavals from the archean period.
proof of rising oxygen in atmosphere
BIF formations, the oxidation of Fe+2 to Fe+3
also cyanobacteria (use Co2 and produce O2)
what is glacial diamicite?
a sedimentary deposit when stones drop from ice flows into underlying mud (ice flow over deep water)
key element 'drop stones'
they are found near the equator proving the ice at equator snowball earth.
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