The Scientific Method
(1) Observation (2) Question (3) Research (4) Hypothesis (5) Tests (6) Results
composition
Materials
continents, oceanic crust, mantle, outer core(liquid), inner core(solid)
Rheology
Behavior
lithosphere(crust & upper mantle, rigid, brittle) asthenosphere(mantle, ductile)
impact craters
created by celestial bodies such as asteroids or meteors slamming into the Earth's crust and leaving a big hole in the ground
Location of volcanoes related to plate boundaries.
Volcanoes form at mid ocean ridges, and on the continental side of subduction zones
Volcanoes appear at MORs because as the oceanic plates split apart, new lava must replace the rock being subducted at the other ends of the plates.
Volcanoes appear on the
spreading/divergent/MOR
A place in the Earth's crust where the crust is splitting apart
Typically seen at mid ocean ridges (MORs)
convergent/subduction/continental collision
A place where two plates are colliding
When an oceanic plate collides with a continental plate the oceanic plate subducts because it is denser.
This creates a subduction zone
When two continental plates converge they slam into each other to create massive
transform
a place where two plates move parallel to the surface and eachother
continental margins: active vs. passive.
Active margin- the place of a subduction zone of a continental and oceanic plate
Passive margin- the continental shelf dips below sea level for some time before reaching an oceanic plate.
Continental drift
the idea that continents have moved and are still moving slowly across the earth's surface
glacial striations
glacier scratches in sediment
leaves evidence
fossils
fossil occurrences proved land animals existed in both paleozoic and mesozoic eras
seafloor magnetic anomalies
Around mid-ocean ridges
Magnetic Stripes that are symmetric above MOR
Strength of earths real dipole field and at a given place
Occurs where basalt has normal polarity
Basalt adds to force to get stronger magnetic signal
seafloor spreading
Divergence at MOR
The MOR pushes rock away at a slow rate to push continents farther away from each other.
The rocks near the continents are old subduct
The rock near the MOR is new and young
Driving forces: ridge push
Ridge push- As the crust around the MOR rises due to mantle upwelling and the extra crust surrounding MOR, the combined forces try to push the plates down and apart.
Driving forces: slab pull
Slab pull- as a part of the oceanic crusts subducts into the mantle, the subducting crust pulls the surrounding crust down in a chain reaction that goes across the entire plate until it reaches the MOR on the other side.
This is more powerful than ridge p
Driving forces: convection
Convection- currents in the mantle that cause continental and oceanic plates to collide. Convection is the underlying force that creates subduction zones and MORs
Definition of a mineral
Solids
Naturally occurring
Inorganic
Crystalline structure
Specific chemical make-up
Atomic structure of elements
All atoms consist of a protons, neutrons, and electrons
The protons and neutrons are in the nucleus and contain most of the atom's mass while electrons orbit the atom in energy shells
Protons are positively charged
Neutrons carry no charge
Electrons are n
ionic bonding
Ionic bonds are created when an atom gives up electrons to another atom
This creates a positively charged cation and a negatively charged anion
Ex: Table salt, (NaCl)
Are relatively weak and can typically be broken if the compound is placed in a solvent s
covalent bonding
Covalent bonds are created when two or more atoms share electrons
The atoms do not create ions nor are they charged
The sharing of electrons is typically much stronger than ionic bonds
Ex: Sugar (C2H12O6)
metallic bonding
Metallic bonds
Metals share electrons freely and electrons can pass from one atom to the next without creating any charges
Electrons can be freely passed from one metal to another
Ex, an electric current running through a nickel and copper wire
Metals are
Silica tetrahedra (charge)
A silica tetrahedral has a charge of -4
independent silicates
Independent silicates are ultramafic
single chain silicates
Single and double chain silicates are mafic
double chain silicates
Single and double chain silicates are mafic
sheet silicates
Sheet and framework silicates are felsic
framework silicates
Sheet and framework silicates are felsic
Polymorphs
minerals with the same chemicals but different structure
phase diagrams and relationship to density
shows change in chemical make-up of minerals at different temperatures and pressure
Location of key minerals in the Earth (olivine, quartz, feldspar)
Feldspar&Quartz found in continental crust Olivine found anywhere deep in the mantle(ultramafic)
Mantle minerals (olivine, spinel, modified spinel, perovskite, postperovskite)
Olivine-Upper mantle
Modified Spinel-Upper mantle
Spinel-Upper mantle
Perovskite-Lower mantle
Postperovskite-Lower mantle
Rocks Definition
a coherent, naturally occurring solid, consisting of an aggregate of minerals or a mass of glass
igneous
created from liquid rock
sedimentary
formed by deposits building up in layers
Clastic- minerals deposits build up over time in layers
Chemical- substances come out of solution and are deposited on the crust
Biochemical- life forms take minerals and create shells or create shelters in the for
metamorphic
Created by sedimentary and igneous rocks changing in a combination of heat and pressure.
The rock cycle
igneous rocks can only be formed by liquid rock
Sedimentary rocks are formed through the weathering and erosion of Igneous, Metamorphic and Sedimentary rocks
Metamorphic rocks are formed when Igneous, Sedimentary, and Metamorphic rocks are put under heat
Melting: thermal
heat transfer?
Melting: decompression
occurs where hot mantle rock rises to shallower depths
Melting: wet
Water pockets get sucked under land, crates addition of heat melting. Occurs in subduction zones.
Bowen's reaction series, its relationship to crystallization/melting temperatures of differentsilicate minerals
The sequence of mineral-producing reactions that take place in a cooling, initially mafic, magma.
Magma differentiation processes (fractional crystallization
cooling magma crystalizes mafic components
mafic minerals get left behind while felsic materials stay in magma
Magma differentiation processes assimilation,
incorporation of country rock into magma
makes magma more felsic
Magma differentiation processes partial melting
increases temperature so only part of the rock melts
melt is more felsic than original rock
Magma migration
fracture the crust/country rock
melt
magma rises because it is less dense. moves through fractures and causes some melting.
Intrusive vs. extrusive textures
EXTRUSIVE: aphanitic,porphyritic, pahoehoe, aa, bombs, vesicles, pumice, ash
INTRUSIVE: coarse, plutonic, porphyritic
Intrusive rocks (granite, gabbro, peridotite)
Felsic----Mafic----Umafic
Granite--Gabbro---Peridotite
Igneous texture
fine grained = extrusive/volcanic, cant see individual crystals cools quickly
coarse grained = intrusive/plutonic,porphyritic, can see crystals cools slowly and at depths
pluton
cooled magma chamber
batholith
a chain of plutons
dike
a vertical planer magma body
sill
a horizontal planer magma body
vein
are monominerolic (containing only one mineral)
Created by hydrothermal fluids
Extrusive rock type variation with composition (rhyolite, andesite, basalt)
Felsic-----Int-----Mafic
Rhyolite-Andesite--Basalt
porphyritic
contains both large and small crystals
pahoehoe
ropey, is relatively hot at eruption
aa
chunky/sharp, is relatively cool at eruption
vesicles
formed when gas escapes cooling lava, often contains trapped gasses
pumice
lava that has many vesicles, often floats in water
aphanitic
no crystals are formed, glassy in appearance
bombs
the volcanic formation from a fountain eruption
ashfall tuff
ash columns?
tuff
pyroclastic igneous rock composed of ash, fragmented lava and pumice
welded tuff
tuff formed by the welding together of hot volcanic glass shards at the base of pyroclastic flows
ignimbrites
pumice-dominated pyroclastic flow deposits with subordinate ash
well-compacted, often partially welded, layers that in some cases resemble lava flows
lahar
massive mudslide
Controlling factors of volcanic eruptive power: silica content, gas content
Silica content affects the viscosity of the magma
The higher the silica content, the more viscous the magma
Gas content affects how violent the eruption will be
Higher gas content creates more violent eruptions
shield
mafic
Shield volcanoes are broad, low-profile features
cinder
Cinder cones
-fountain eruptions
-relatively small
-1 eruption
-cinder sand
-near larger volcanoes
stratovolcano
Their lower slopes are gentle, but they rise steeply
form at convergent plate margins, where one plate descends beneath an adjacent plate at the site of a subduction zone.
ash flow
Ash flow Volcanoes
-"big beasts"
-super volcanoes
-pressure gets so hot that it explodes and it collapses on itself
-creates a caldera
-lots of volume
-felsic magma
-viscosity important
fissure eruptions
fissure eruptions are generated at several contemporaneous sites along a linear fracture
Hazards pyroclastic flow
-really dangerous, horrible, hot gas, moving faster than anything else
-extremely strong blasts
Hazards lahars
-when snow melts and mixes with ash and creates mud flows
-mudslides
Hazards ash
-have warning systems
-USGS
Volcanoes and climate
-ash can cool down the earth when ash covers sun
Why study geology?
major pattern is plate tectonics and to discover what rocks are made up of
How do we study geology?
Observations,
calderas
formed when a volcano becomes dormant and erodes. The volcano eventually collapses into its massive lava chamber and a caldera is formed.
salt domes
created when salt veins reach the Earth's surface and rain dissolves and washes the minerals away leaving a crater in the ground.
Location of earthquakes related to plate boundaries.
Earthquakes occur along plate boundaries and are caused by movement in the crust
This movement can be a subduction, a "push" on a continental collision boundary, a spreading at an MOR boundary, or two plates moving rapidly past each other in a transform b
atomic number
Atomic number is determined by the number of protons an atom has in its nucleus
atomic mass
Atomic mass is determined by the number of protons and neutrons located in the nucleus Atoms with the same number of protons but differing numbers of neutrons are called isotopes
formation of ions
There are two types of ions called cations and anions and are formed when an element gains or loses electrons
Cations are positively charged ions
Were created when an element lost its outer electron shell to be reduced to a full electron shell at a lower
continental crust
felsic
Density=2.7
42km thick
oceanic crust
mafic
density=3.0
8kn thick
mantle
ultramafic
density=3.3
Mafic
igneous rocks or magmas that are rich in iron and magnesium but relatively poor in silica
Felsic
igneous rocks that are rich in elements forming feldspar and quartz
Ultramafic
igneous rocks or magmas that are rich in iron and magnesium but poor in silica