What is the principal of uniformitarianism and how is it applied by geologists?
� The principal of Uniformitarianism means that "The present is key to the past" -James Hutton. Geologists use this because they can compare observations today to the past preserved in rock record.
How did the Earth's moon form?
Why is the Earth's orbital plane tilted?
� a Mars-sized body collided with the earth - Resulting in:
� 1) the ejection of debris into space forming our moon
� 2) Sped up the Earth's rotation
� 3) shifted Earth's orbital plane to 23 degrees because it has to hold the moon in its orbit
what is the nebular hypothesis and how it applies to the formation of our Solar System (sun and planets).
� The nebular hypothesis means that a nebula (an area which is made up of mostly dust) starts to collapse under its own gravity and stars form in the center. Then it spins faster and flattens out into a disk. The dust starts to clump and could explain how
How does density change with depth? What are these zones?
How are these zones grouped?
Which one makes up the tectonic plates? Which zones are strong and which ones are weak or ductile?
� Density changes with depth
� The tectonic plates- forms the outer most rigid layer of the lithosphere it is either: 1. continental or 2.oceanic
� The lithosphere STRONG (lithos = stone) - forms the strong outer shell and includes the crust and part of t
How old is the Earth?
4.53 billion years old
how did earths continents form?
Continents - formed from the lighter molten materials rising to the surface due to differentiation and solidified as it cools
how did the earths atmosphere and oceans form? (2 theories)
� The atmosphere and oceans formed in 1 of 2 ways resulted from the impact of volatile-rich matter on the Earth from space early when it was in a moldable form. Remember the large planets like Jupiter are largely formed from frozen gases
� Or they came fr
The Earth has an external heat engine and internal heat engine.
Why are they important?
Where did the heat energy(s) originate which powers the internal and external heat engines?
� External heat engine - Solar Energy from the sun is the driving force powering the weather and climatic conditions. Solar energy affects the Atmosphere, Hydrosphere, and Biosphere
� Earth's internal heat engine - is powered by heat energy trapped during
What is the theory of plate tectonics?
What is the driving force behind plate tectonics?
� The outer portion of the earth the lithosphere, is not a complete shell but is broken in units called plates. There are about twenty distinct pieces.
� The plates move! Plates act as rigid units that ride on the asthenosphere, which is also in motion. P
What is the continental drift hypothesis as advanced by Alfred Wegner?
What evidence did he use to support his hypothesis?
With so much evidence why was it not elevated to? a theory - what were some of the problems?
What was Pangea
� suggested that the plates fit together
� Patterns of present day animal life
� Fossil evidence (Mesosaurus)
� locations of past Galaciations
� the distribution of climatic belts
-he could not prove it but he thought that the plates at one point all fit
What evidence was found that supported sea floor spreading?
What is magnetic stripping?
How and where does it form?
Sea Floor spreading is found in magnetic stripping which is basically like that of a tree trunk, each stripe or ring is based is formed each year. Based on the poles and the location of the rock you can see how the plates are shifting in relation to the e
What is the "Ring of Fire"?
What relevance does it have to plate tectonics?
� The ring of fire is the chain of volcanoes that are on plate boundaries. This supports the theory of plate tectonics because it says that the boundaries move
What type of plate boundary do earthquakes occur at?
What type of plate boundary do volcanoes occur at?
� A volcano would occur at a Divergeant boundary where the plates move away from one another
� An earthquake would occur at a convergeant boundary where they collide.
What are the three main types of plate tectonic boundaries and any subdivisions of each?
What are the plate motions relative to each other?
What are the stresses associated with each?
Are there any features associated with these boundaries (mid-ocean ridg
� Divergent: Move away from each other in a process called sea-floor spreading. Decompression melting (pressure reduced as it rises which causes melting). Tensional stress
� Convergent: move towards each other and one plate subducts beneath another for oc
What causes the plates to move?
what is convection?
what is Ridge-push force?
What is slab-pull force?
� Convection (hot athenosphere rises in some places and sinks in others and causes convection flow
� Ridge-Push Force: when a plate pushes against the other because the surface of the sea floor is higher than the plains and gravity therefore causes the el
Where do you find "black smokers"?
� At a mid ocean ridge
The oldest ocean crust dates to about 200 my and the oldest continental crust dates to about 4 by. Why the big difference?
� This is due to sea floor spreading
What determines which plate will subducts? What is decompression melting and where would this occur?
What type of crust forms there?
� The density of the plate will cause it to subducts. Decompression melting corresponds with a divergent boundary. This is when the pressure lessens causing the magma to heat into liquid form and then it bubbles over cools and forms oceanic crust
What is flux melting and where would this occur at (boundary type and subdivision(s) and location in subduction zone)?
What type of crust is destroyed there?
Is any new crust created there?
How deep are the plates recycled to?
� Partial melting in a subduction zone. This would happen at a convergent boundary with oceanic crust. New crust is created through the rising magma that is melted at the bottom.
How is continental crust created?
What type of plate tectonic boundary(s) is continental crust created at?
� Convergent boundaries: with flux melting due to accretion new land is attached to existing land in the subduction case. Or it is formed through collisions where the crust changes shape.
What are hot spots?
Where would you find them?
Do they create or destroy oceanic or continental crust?
What feature/landform do you find above them?
� Hot spot volcanoes form above plumes of hot mantle rock that rise from near the core-mantle boundary. As a plate drifts over a hot spot it leaves a chain of extinct volcanoes. The create continental crust.
What is a mineral?
A mineral is a naturally occurring solid, formed by a geologic process that has a crystalline structure and a definable chemical composition and inorganic.
What is an isotope? How can they be used in geology?
a different version of a given element that has the same atomic number but different atomic weights
Understand what chemical bonding is and the difference between ionic and covalent bonding?
Which bonding type is the strongest?
Ionic bonds form when a cation (+) and anion (-) (ions with opposite charges) get close together and attract eachother.
Covalent bonding is when atoms share electrons and this is the strongest bonding type
How do minerals form?
What determines which minerals will form at a given location?
What conditions cause minerals to form?
Minerals can form by the freezing of a liquid (Ice Crystals)
Minerals can form by solid-state diffusion, the movement of atoms or ions through a solid to arrange into a new crystal structure
Minerals can form through biomineralization
Minerals can form by
Be familiar with the mineral properties
color
luster
streak
cleavage
fracture
hardness
density
crystal habit
specialty properties
Color: the way a mineral interacts with the light
Streak: the color of the powder produced when scratching the mineral
Luster: the way a mineral surface scatters light (metallic, non-metallic, silky, glassy, satiny)
Hardness: measure of the ability of a m
What are mineral polymorphs?
What are the polymorphs of carbon?
Two different minerals (diamond and graphite) that have the same composition but different crystal structures
What is the most abundant mineral group in the crust?
The silicate rock classification is based on their crystal structure. Are there other mineral groups besides silicates?
What are some of them?
Silicate minerals make up 95% of continental crust. Crust is made up of mostly silicon-oxygen tetrahedron. These also make up the crust: Carbonates, Oxides, Sulfides, Sulfates, Native Elements
Are all the different minerals included in the group of asbestos minerals carcinogenetic or linked to lung disease?
Not all types, only some.
What makes a gem?
What are some of there characteristics?
A gem is a cut and finished stone ready to be set in jewelry. There are rare and not so rare stones.
Where do diamonds come from?
Are they brought up from the mantle to the surface fast or slow?
How hard is a diamond (on Mohs hardness scale)?
Diamonds consist of mostly carbon which accumulates only near the earths surface. Diamonds are made about 150 km under the surface: need extreme heat and pressure. About a 10 on mohs scale. They move out of the mantle fast.
What are the three main rock types and what processes (melting; weathering; metamorphism) cause them to form?
1) igneous rocks: form by freezing (solidification) of molten rock or melting
2) sedimentary rocks: form by cementing together fragments (grains) broken off preexisting rocks of by the precipitation of mineral crystals out of water solutions at or near th
What is the most abundant rock type in the Earth's crust?
What is the most abundant rock type we find on the land surface?
Igneous rock is the most abundant rock type in the Earth's crust.
Understand the rock cycle in a plate tectonic setting, in the context of identifying where any particular rock type is likely to be found/deposited. Also, understand the rock cycle in context of how one rock type can be changed to another. Refer to lab ma
Igneous (cooled magma) -> weathering, eroding, deposited-> sedimentary (cemented together) -> weathering, eroision, depositing, compacting -> metamorphic temp higher as it gets deeper -> melting exploding & cooling
How are igneous rock formed?
What are the two types of igneous rock?
How does the location where they cool affect the speed of cooling and there crystal size?
Igneous rocks form by cooling of magma underground or lava at the surface. There are intrusive and extrusive igneous rocks. The extrusive ones they cool quickly and have a glassy texture (out of the magma chamber). The intrusive rocks grow together to for
plutonic
volcanic
intrusive
extrusive
aphanitic
phaneritic
porphyritic
pegmatitic
glassy
vesicular
pyroclastic
What does each texture indicate about the rate of cooling?
Intrusive: cools slowly, large crystals (ex. Granite)
Extrusive: cools slowly, small crystals
Plutonic: Large igneous bodies that cool underground (intrusive)
Volcanic: consists of larger fragments of volcanic debris
Aphanitic no identifiable minerals (gr
Where are magmas generated?
What makes magma?
How do rocks melt (3 ways)?
Give an example of the plate tectonic setting that corresponds to each way.
Magma is made of mostly silicon and oxygen but also contain various other elements.
1. rocks can melt by partial melting: only 2-30% of a rock melts to create magma (not hot enough)
2. flux melting: where volatiles enter hot mantle; this happens at subduc
How do the factors of partial melting and where the melting takes place affect the composition of the resulting magma?
The first formed melt will be richer in silica than the original rock. As melting continues, magma becomes more mafic.
Igneous rocks are classified based on there silica composition.
What are the four composition groups?
What is there relative melting temperature order for the compositional groups?
How do Fe -Mg and Si -Na-K vary in the groups?
What minerals would you exp
Magma is
-Felsic: 66-76% silica (light)
-intermedate: 52-66% (medium)
-Mafic: (45-52%) Dark has a large amount of Fe and -Mg
-ultramafic (38-45%) really dark
How does viscosity vary among the compositional groups?
How is this related to the magma temperature and magma composition?
Silica-poor lava (basaltic) is less viscous and flows farther (mafic)
Silica-rich lava (rhyolitic) is so viscous it may pile up (felsic)
From magma to igneous rock: What process is involved?
What is fractional crystallization?
Why does this change the composition of the remaining magma?
Igneous (cooled magma) -> weathering, eroding, deposited-> sedimentary (cemented together) -> weathering, eroision, depositing, compacting -> metamorphic temp higher as it gets deeper -> melting exploding & cooling
Fractional crystallization: when mafic m
intrusions
sill
dike
batholith
vein
Where do they form?
How does magma make its way to the surface?
Dike: a tabular intrusion that cuts across preexisting layering (bedding or foliation)
Sill: a tabular intrusion that injects parallel to layering
Batholith: multiple slabs of igneous rocks over 100 km long
Effusive eruptions:
� Gentle
� Lava
� Low viscosity, low silica, high temp
� Divergent boundary and hot spots
� Kilaua, Hawaii and mid-atlantic ridge
� Release of gas
Pyroclastic
� Violent eruptions
� High viscosity, high silica, low temp
� Traps gas
� Convergent boundary & continental hot spots
� Mt. St. Helens
1. Flood eruptions
� Fissure
� Mafic
� Flat layers
� Columbia river basalt
2. Cinder cones (most abundant)
� Vent
� Mafic lava & pyroclastic rocks
� Steep slopes
� Spits out pumice balls
3. Shield Volcanoes
� Vent or fissure
� Mafic
� Broad gentle slope
4. Splatter cones
� Vent
� Mafic lava
� Steep slope