internal patterns of a rock; orientation & size of grains/crystals INSIDE.
felsic to mafic. In between = intermediate. Type depends on proportion of free quartz, Feldspars, Fe-Mg minerals.
type of igneous rock; cannot see individual crystals
type of igneous rock; can see individual crystals
type of igneous rock; started cooling and was shot up
type of igneous rock; shot up, cooled too fast, cannot form crystals.
type of igneous rock; shot up from volcano, formed air bubbles/vesicles.
made from another rocks, organisms or chemical changes. Carried in a fluid, deposited and lithified, or precipitated. Clastic and Chemical
transformed from sediment to rock
Clastic / detrital
type of sedimentary rock; mechanical breakup of other rocks. Named after clast = grain size.
ANISOTROPIC (will not break the same way, but can find weakpoints (where material meets)). porous. Generally hard. 5.5-7
type of sedimentary rock; crystals form from precipitation or growth from solution. may have large biological components. mobile. Organic or inorganic, isotropic-anisotropic, soft 2-4, soluble. SENSITIVE TO WATER AND PH. We build with them.
round against other grains
angled against the grain
type of sedimentary rock; congolmerate or breccia rock.
2 – >0.0625
type of sedimentary rock; sandstone
0.0625 – >0.004
type of sedimentary rock; silstone, shale
type of sedimentary rock; claystone, musdtone, shale
Organic chemical deposit
type of sedimentary rock; skeletal remains or excretions. Limestone or chalk.
Inorganic chemical deposit
type of sedimentary rock; precipitation due to evaporation.
made from pre existing rocks; recrystallized without melting, crystals got bigger/rearranged/recomposed. MOSTLY anisotropic, can be iso. Some characteristics of old rock remain. Crystaline/BENT LAYERS. hardish elongated NON-POROUS
Types of metamorphic rocks
Caused by changes in pressure or tempertaure, buried. Contact or regional.
Cooling of a plutonic body (solidified magma chamber). 100’s of meters.
Stress and heating related to plate tectonics. 100’s of KMs.
preferred orientation in elongation; is a weakpoint.
Transition of a rock into another type via processes: Weathering, sedimentation, lithification (sedimentary) Heat & Pressure causing recrystallizing and deformation (metamorphic. Melting and crystallization (igneous)
Large scale movement of the lithosphere (crust) or asthenosphere (partly molten upper mantle). WHERE THINGS GO WRONG.
Plate Tectonic theories/history
Snider 1855 – Puzzle idea Wegener 1912 – Continental drift Du Toit 1937 – Gondwanaland, glacial deposit, ice movment
Visual evidence of plat tectonics
99% of continents fit, similar environment across oceans, marine fossils far from ocean.
Magnetic minerals align themselves with the magnetic point of earth when at the curie point
Polar wandering curves
60’s, Irving. Alternating strips of magnetic north on ocean floor. Cracked floor, magma pours up, aligns to current magnetic north.
oceanic = 200 Ma continental = 3.96 Ga
opening and closing of the oceans. made super continents. Have had at least 3 of these.
Hot material moves up, little comes through the crust, rest goes to the side. Gravity pulls heavy plate down.
Movement rate & directions
plates move around 2-3 CM a year. hawaii like places move 11.
3 plate types
divergent transform convergent
Divergent plate boundary
move apart due to mantle uprising. Tensile thinning, lots of volcanoes in upper 12 KM. Creates new crust. ICELAND.
Transform plate boundary
Plates move past each other; shearing displacement. ripping. LOTS of shallow earthquakes, mostly moderate. No volcanoes. SAN ANDREAS
Convergent plate boundary
Plates bump into each other. Denser plate subducts; deep trenches, volcanoes, earthquakes. Lighter plate will obduct; build mountains.
continental-continental = butt heads, huge mountains, volcanoes are hard to reach surface. oceanic-oceanic – form islands and volcanoes oceanic-continental – classic; makes rocky mountains.
Sudden slippage (rupture) along fault zones in response to stress. Seismic slip
Disruption and displacement of sea floor. 1000kph. Increases in frequency as approaching shore. High magnitude =/= mean tsunami
Indian ocean Tsunami Warning System. ? Monitors sea level data and the rate of lateral change Issue warnings, including expected time of arrival and possible wave heights Only works if the tsunami originates far enough away
Fire from Earthquakes
Usually more damaging than the quake itself. Water lines are often broken.
Some material is prone to slipping, quake is just the trigger. Most ground isn’t “Stable”.
Volcanic island that had coastline collapse.
Change in arrangement of water in structure of clay/sand. Shaking makes a slurry. Common in marine clays (they are held together by salt).
Sand from below mixes with water, becomes less dense, floats up. Rolls downhill.
Results from loss of sanitation, shelter, contamination,
With pattern recognition, we can estimate when events make an earthquake likely.
Risk assessment principles
Assume stresses act continuously. Faults with lots of seismic activity ARE safer. Look for seismic gaps/earthquake cycle.
Short term prediction
Compare changes to normal background noise. Precursor phenomena: Drops in seismic waves Uplift/tilting ground Increased radon in water Geophysical changes Anomalous animals Increase in ground temperature.
Controlling strain release
#1 fluid injection – lubricate fault system. Rocky mountain chemical pumping. #2 Explosives – release small quakes. Or HUGE ones. Liability issues.
doesn’t shake buildings as much
Remove excess water. Want SOME. too much is the issue.
Slack in linear structures
Accommodate seismic activity. Pipelines that will move.
Fluid magma temperature
Composition of magma
Depends on geography. SiO2, Fe, Mg, others.
Amount of SiO2 in magma
determines melt type, melt viscosity, gas release ability.
rock types determine what melts. Little bits will melt and head towards low pressure.
Magma gas release
More SiO2 makes for cooler, more viscous magma that hardens faster, and traps gas.
Places to avoid during volcano
Areas with silicate rich magma (continental & water rich material) Subduction zones Continental hot spots/mantle plumes
Stationary locations in planet; plates move over top. Possible sites of heat making radioactive elements.
Types of mafic volcanic eruptions
Fissure, shield, cinder cones
Runnier (less silica), so less volatile.
Majority of all volcanic activity; occurs along spreaking ridges and drifts, low hazard/risk.
Is a fracture(s). Multiple exit points; one main vent fed by multiple feeders. No guarantee WHERE it will erupt. Not very viscous, flows downhill easily, covers a lot of area. Kilawaya; lots of activity. Watch at night to see activity. Hawaii is actually 10KM high and 100KM across!
Found with various compositions ? Common with gaseous mafic lavas ? Small (generally ? Fairly symmetrical, steep sided (~35°) cones don’t really hold lava. Pimples on the island. SHORT LIVED features. Lava in area is viscous and gassy. ONE vent. Plugs up itself. Pressure blows it up.
Shallow dipping slopes ? Thick and spatially extensive Lots of lava, extends over a large period of time. They formed the hawaiian islands. Affect the climate.
Is a fracture(s). Multiple exit points; one main vent fed by multiple feeders. No guarantee WHERE it will erupt. Not very viscous, flows downhill easily, covers a lot of area.
Felsic, intermediate. High, steeped. Made of volcanic rubble. Cools rapidle.
? AKA stratovolcanoes ? Intermediate to felsic lavas ? Steep sided, large and explosive ? Layered ? Related to subduction zone Snow and ice.
? Large, negative features ? NOT restricted to volcano type or composition ? Eruption is sudden and often catastrophic ? Formed by one of two methods: 1)Phreatic eruption 2)Collapse
Do NOT erupt frequently. When they do erupt, it is bad ass.
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? Explosion caused by water boiling in pores and fractures ? Generally occurs in volcanoes adjacent to or surrounded by water ? Example: Krakatau, Indonesia 1883 All eruptions are phreatic, technically.
? Rapid emptying of the magma chamber during eruption ? Chamber collapses Example: Mt. Mazama, Oregon ~6800 BP
? Hot, fragmented, welded or solidified volcanic material ? Range from ash (1/16 mm) to bombs and blocks (house-sized) ? Eruption can cause shockwaves ? Types: ? Volcanic ash eruption ? Volcanic ash flow (Nuees ardentes)
Volcanic ash eruption
? Mainly ash and dust (Very soft; pulverized glass and rocks. Gets everywhere. Just like lime; mixes with water and becomes concrete. Is super acidic. Slippery. Super heavy when wet.
Volcanic ash flows
AKA: nuees ardentes; grey eruptions • Hot, dense clouds of ash and gases • Speeds can easily exceed 100 km/hr • Temperatures often >1000°C • Unpredictable • Generally associated with composite volcanoes most common death of volcanologists.
Both a primary and secondary event. Causes flooding elsewhere, as it displaces water. Happens when you have sources of water near the eruption. Downhill; follows any drainage patters. SUPER thick. Will pick up stuff. Things float really well; like buildings. Primary = melting snow and ice Secondary = ash has fallen and rain begins
Rare to kill; mostly bad luck. Do not generate enough to kill people. ? Generally dense like CO and CO2 . ? Not usually a problem ? Build up in water may be a hazard
Volcanic fog/smog – VOG
Gasses & particles of ash. Parts of volcanic national parks are often closed from vog
Secondary Volcanic effects
? Indirectly caused by the eruption ? Usually atmospheric, but there are others! ? Short or long-term ? Duration depends on layer of atmosphere or size of land area affected ? Severity depends on amount of material ejected ? Localized or widespread
Volcanic 2ndary atmospheric effects
If in the stratosphere: ? Affects are global and long-term ? Affects global temperatures (blocks sunlight) If in the troposphere: ? Local temperature changes and effects ? Short-term (
SO2 from sulphide gases emitted during the eruption ? In troposphere: removed as acid rain ? In stratosphere: stays for years ? Can circle the globe ? May cause ozone depletion
ash with water (melted snow and ice)
ash with rain from volcano
3, now 4 ways Active, Dormant, Extinct, Erupting. Active – last 10,000 Dormant – not in last 10,000. CAN still erupt. Long wait. Extinct – Unlikely to ever erupt again. Cinder cone… ON TOP OF something active.
swarms in earthquakes. Sudden increase. harmonics; two signatures. A type is rocks breaking. B type is the harmonic; often masked, sound of magma moving.