Geology Review Q2 (Complete)

IGNEOUS ROCKS, VOLCANOES, SEDIMENTARY ROCKS, METAMORPHIC ROCKS, EARTHQUAKES

Earthquake Prediction

Long-term statement that an earthquake will occur in a region

Tsunami

Earthquake hazard: Large waves triggered by displacement of seafloor for submarines earthquakes

Liquefaction

Earthquake hazard: Fluid-like behavior of water-saturated sediments in response to earthquakes

Ground Failure

Earthquake hazard: landslides triggered by ground shaking

Fault Rupture

Earthquake hazard: Displacement of ground surface along fault traces

Ground Shaking

Earthquake hazard: Trembling/shaking of land, causes structures to vibrate, affected by resonance

Plate Boundary Seismicity

Idea that most earthquakes occur near plate boundaries where sliding is most common

Magnitude

Amount of energy released during an earthquake: measured with Moment Magnitude (1-10)

Earthquake Location

Found using intervals from P- and S- waves, multiple stations to triangulate location

Surface Wave

Seismic waves that travel on surface, causes destruction, R/L

R-Wave

Seismic waves: Surface wave that rolls ground in oval motion, DESTRUCTIVE

L-Wave

Seismic waves: Surface wave that laterally move ground with no displacement, LESS DESTRUCTIVE

Body Wave

Seismic waves that travel in earth’s interior, no destruction, P/S

P-Wave

Seismic waves: longitudinal wave parallel to travel, primary energy movement, FAST (4-7km/s), (slinky)

S-Wave

Seismic waves: transverse wave w/ shearing motion, secondary to first wave, SLOW (2-5km/s), (rope)

Elastic Rebound Theory

Method of creating earthquakes, defined by stick-slip behavior (breaking ruler)

Active Volcano

Forecasting: volcano has erupted frequently and will most likely continue (Mt Etna)

Dormant Volcano

Forecasting: volcano has erupted before but not in living memory (Mt Fuji)

Extinct Volcano

Forecasting: volcano has not erupted in thousands of years, usually eroded (Tamu Massif)

Lahar

Volcanic hazard: Secondary, fast-moving water and rock from volcano (Nevado Del Ruiz 1985)

Degassing

Volcanic hazard: Secondary, volcanic gas released between eruptions, comes out through fumaroles

Pyroclastic Density Currents

Volcanic hazard: Primary, FAST clouds of hot gas/volcanic matter, obliterates in seconds (Pompeii)

Ashfall

Volcanic hazard: Ash remains in air for long periods of time after eruption, thins out with distance from volcano, made of glass (Mt. St. Helens)

Lava Flow

Volcanic hazard: Structures are burned due to thick flowing (Kalapana, HI)

Volcanic Explosivity Index (VEI)

Logarithmic scale used to measure amount of erupted material from 0-7

Pyroclastic Deposits

Accumulated fragments (tephra) ejected from volcano: Ash, Lapilli, Bombs, Blocks…

Pahoehoe Flow

Lava flow: Mafic, smooth rope surface with flow underneath, sometimes in ‘lava tubes’

A’a Flow

Lava flow: Mafic, partially solid/jagged surface, moves as pasty mass

Effusive Eruption

Mafic lava flow w/ low viscosity, usually slower

Explosive Eruption

Felsic lava flow w/ higher viscosity, usually faster, debris ejected into air

Magma Viscosity

Magnitude of resisting friction/lava flow, increases w/ more silica content and decreases / temperature

Stratovolcano (Composite Cone)

Morphology: Intermediate in slope/size, cinders build steep sides, capable of effusive/explosive eruptions

Cinder Cone

Morphology: Made of pyroclasts, very steep, smaller than normal,

Shield Volcano

Morphology: Gently-sloped, made of solidified lava, very broad

Caldera

Volcano anatomy: expanded crater occurring and growing after large eruptions

Crater

Volcano anatomy: found at summit, hole which magma escapes/erupts

Edifice

Volcano anatomy: landform made from accumulation of erupted material, makeup of volcano

Magma Chamber

Volcano anatomy: scales the height of volcano, contains magma to feed through conduit

Conduit/Fissure

Volcano anatomy: connector from magma chamber to vent

Vent

Volcano anatomy: hole in volcano where magma escapes/erupts, stems from conduit

Volcano

Landform built from products of eruption, built from vent

Glassy (Texture)

Igneous textures: No visible mineral crystals, VERY rapid cooling, high silica content

Porphyritic (Texture)

Igneous textures: Large crystals amid non-visible crystals, indicates slow then sudden rapid cooling, usually extrusive rocks

Aphanitic (Texture)

Igneous textures: fine-grained crystals unseen with the naked eye, indicates rapid cooling, extrusive rocks

Phaneritic (Texture)

Igneous textures: Visible coarse-grained crystals, indicates slow cooling, intrusive rocks

Intrusive Rocks

Igneous rocks that cooled under Earth’s surface, usually aphanitic textured, formed with minerals under high temperatures (granite)

Extrusive Rocks

Igneous rocked that cooled above Earth’s surface, usually phaneritic textured, gas vesicles formed (basalt)

Bowen’s Reaction Series

Details rate and order of minerals cooling into crystals, starts ultramafic (olivine) and goes to felsic (quartz) with decreasing temperature

Partial Melting

Magma composition: Some minerals melt earlier than others, runs from mafic to felsic, relative to source rock, opposite of fractional crystallization

Fractional Crystallization

Magma composition: opposite of partial melting, crystals are removed from magma with respect to mineral composition

Magma Mixing

Magma composition: Combining of two different melts of different compositions, can form new melts

Assimilation

Magma composition: incorporation of surrounding rock into magma

Source-rock Composition

Magma composition: Magma composition usually reflects the source rock in which it came from

Heat-transfer (Melting)

Melting: hot rocks soften adjacent cooler rocks to form magma, common near volcanoes

Flux (Melting)

Melting: melting temperature is reduced through volatiles like water or CO2, common near subduction zones

Decompression (Melting)

Melting: mixture of high temperature and lowering pressure, rocks move from Geotherm curve to Solidus to Liquidus

Felsic (Composition)

Igneous composition: Highest silica content (Quartz)

Intermediate (Composition)

Igneous composition: mid-level silica content (Plagioclase)

Mafic (Composition)

Igneous composition: low silica content (Pyroxene)

Ultramafic (Composition)

Igneous composition: very low silica content (Olivine)

Igneous Rocks

Rocks formed from the solidification of magma or molten rock with a crystalline texture and silicate minerals

Sedimentary Basin

Stored with sediment over time to be preserved, size is determined by sea level and subsidence (sinking)

Fossils (Sed. Rocks)

Floral and faunal assemblage, helps denote type of environment land once was

Mudcracks

Sedimentary structures: cracks in the surface of bedding resulting from wetting and drying cycles

Ripple Marks

Sedimentary structures: ridges that form on surface bedding from wind or water, informs of depositional environment, preserved in beds ‘cross-bedding’

Bedding

Sedimentary structures: arrangement of sediment into distinguishable bounds, reflects origins through thickness, presence, variability

Sedimentary Structure

Layering/arrangement of grains in clastic rocks

Transport Distance

Clastic characteristics: roundness of grains decrease, grain size decreases, sorting increases

Transport Medium

Clastic characteristics: controls max grain size, water/ice/wind/mass wasting

Roundness

Clastic characteristics: shape of grain, runs from Angular to Rounded, increases w/ weathering

Sorting

Clastic characteristics: uniformity of grain size, runs from Very Poorly to Very Well

Grain Size

Clastic characteristics: runs from Mud to Boulders, founds within clastic rocks, sorted by length

Lithification

Rock formation: sediment is compacted, condensed into solid rock

Detrital (Rocks)

Rock formation: sedimentary rocks that undergo lithification (breccia)

Biogenic (Rocks)

Rock formation: sedimentary rocks comprised of animal shells in marine environments (chert)

Organic (Rocks)

Rock formation: sedimentary rocks comprised of accumulated live matter (coal)

Chemical (Rocks)

Rock formation: sedimentary rocks formed by precipitation of minerals from surface-water solutions (rock salt)

Spheroidal (Weathering)

Weathering: chemical weathering resulting from water entering into a rock and peeling off layers

Oxidation

Weathering: chemical weathering combining oxygen and iron (rust)

Incongruent Dissolution

Weathering: chemical weathering where only some ions are lost through dissolution to form new compounds (hydrolysis)

Congruent Dissolution

Weathering: chemical weathering where all mineral is completely dissolved

Dissolution

Weathering: Breakdown of mineral into aqueous components

Chemical (Weathering)

Weathering: Materials undergo changes to match environment equilibrium

Thermal Expansion

Weathering: physical weathering where cracking occurs due to repeated heating/cooling of rock

Plant Wedging

Weathering: physical weathering where root growth in joint, fracture, or bedding causes expansion

Salt Wedging

Weathering: physical weathering where salt growth in joint, fracture, or bedding causes expansion

Frost Wedging

Weathering: physical weathering where ice crystal growth in joint, fracture, or bedding causes expansion

Jointing

Weathering: physical weathering where applied/released stress develops a natural fracture

Physical (Weathering)

Weathering: Processes that break rocks into smaller parts w/ no change to mineral composition

High Grade (Metamorphism)

Metamorphic grade: highest temperature and pressure, close to partial melting (gneiss)

Intermediate Grade (Metamorphism)

Metamorphic grade: Some temperature and pressure (schist)

Low Grade (Metamorphism)

Metamorphic grade: Little temperature and pressure, close to shale (slate)

Regional (Metamorphism)

Metamorphism over wide areas and considerable depths, associated w/ orogenesis, Mid T L/H P

Hydrothermal (Metamorphism)

Metamorphism in presence of water, Low P/Low T, produces ore minerals

Contact (Metamorphism)

Metamorphism adjacent to igneous intrusions, High T/Low P, produce non-foliated rocks

Metasomatism

Metamorphism w/ introduction of ions from external source

Protolith Composition

Metamorphism factors: mineral content of metamorphic rock is same as chemical composition of parent rock unless changed w/ fluids trapped inside rock (Limestone→Marble)

Foliation

Metamorphism factors: alignment of mineral grains/sedimentary particles, applied w/ differential stress

Differential Stress

Metamorphism factors: different magnitudes of stress in different directions, leads to foliation

Confining Pressure

Metamorphism factors: applied equally on all sides of a surface (submarine)