Earth Science

catastrophism

earth began as a molten ball, as it cooled went through a series of intermittent global convulsions. All independent creations (religious dogma)

Uniformitarianism

(gradualism) the present is the key to the past, processes observed today happened in the past and will continue to happen at similar rated over unlimited time

Oldest matter

found in meteoroids, obtained from primitive asteroids. Formed 4.567 billion years ago same as solar system

Oldest mineral

crystal of zicron 4.404 billion years

earths age

4.54 billion years (meteoroids average age)

Principle of Superposition

sedimentary rock layers are desposited on top of each other

Principle of Original Horizontality

they layers are flat when they are deposited

Principle of Original Lateral Continuity

they are deposited over wide areas

Principle of Cross Cutting Relationships

a fault is younger than the youngest rock it cuts, strata above an unconformity is younger than the strata below, any feature that cuts across a rock must be younger than the rock it cuts

Principle of Faunal Succession

same layer in different parts of the country based upon its fossil content

Unconformities

horizons representing a time break during which erosion of a rock sequence took place prior to the deposition of a more recent sequence

Subdivisions of Time

designated by the emergence and extinction of fossil life forms, eras are global extinction events

Radioactivity

the progressive breakdown of the nucleus of an atom or isotope

Relative Age Dating

determines the chronological order of events and rock layers using stratigraphic principles without needing numerical years

Absolute Age Dating

uses radiometric decay of radioactive isotopes to assign precise numerical ages to rocks and geological boundaries

Dynamo Model

electric currents are generated by enormous dynamos driven by circulating hot currents in the liquid metal outer core and magentic fields surround these electric currents

Layers of the Earth

inner core, outer core, lithosphere, asthenosphere

Inner Core

solid metal ball (iron), roughly as hot as the suns surface (5000-7000)

Outer Core

thick layer of liquid metal driving earths magnetic dynamo model

Lithosphere

the rigid brittle outer shell consisting of the curst and the outer portion of the mantle

Asthenopshere

the hot plastic mobile part of the upper mantle beneath the lithosphere

Seafloor Spreading

proved through magnetometers recording magnetic striping patterns and radiometric dating of basalt rocks

Spreading Rate of Seafloor

rate = distance/time

Paleomagnetism

the study of earths magnetic field through rock magnetism

Subduction Zones and Trenches

mark convergent boundaries where cold, dense oceanic lithosphere is compressed, breaks and sinks back down into the asthenosphere

Transform Faults/Boundaries

breaks where tectonic plates slides horizontally past one another without creating or destroying curst

Divergent

tensional stress where plates pull apart (spreading centers)

Convergent

compressive stress where plates collide (subduction zones)

Transform

shearing stress where plates slide past each other

Hot spots and Mantel Plumes

stationary columns of hot magma rising from the core-mantle boundary, formed by deep thermal anomalies creating large reservoirs of magma to push upward against lithosphere

mantle

large volume, dense silicate and oxide minerals (mesosphere, asthenosphere, lithosphere)

Mesosphere

lower thick zone, very dense rock behaves as a solid

Differentiation

process of heavy material moving to the planets core and lighter material outwards

Accretion and Impact Heating

kinetic energy liberated during impact

Core Formation Heat

when initially homogeneous planets sort themselves out into their structures release of gravitational potential energy

Heat From Dissipation of Tidal Energy

gravitation pulls from the sun and moon create small tidal distortions in earths mantel, braking earths rotation and converting that energy into heat

Heat From Radioactivity

radioactive isotopes undergo decay releasing particles and energy

Short Lived Radioactivity

abundant in early earth and now virtually extinct, providing massive early heat

Long Lived Radioactivity

isotopes like K, U, Th that produced heat through early history and continue to do so

Normal Faults

caused by tensional stress which results in crustal lengthening and one side slipping down

Reverse and Thrust Faults

caused by compressive stress where rocks on one side are pushed over the other at a low angle resulting in crustal shortening

Strike-Slip or Transform Faults

caused by shear stress which results in a tearing or lateral motion

Elastic Deformation

reversible deformation where the rock springs back if stress is released

Plastic Deformation

non reversible deformation under higher stress

Brittle Failure

sudden fracture and fault slip which produces an earthquake

Elastic Rebound Theory

progressive tectonic deformation causes rocks to bend and following rupture, both sides snap back to their original straight shape, releasing stored energy

Focus/Hypocenter

the exact along the fracture plane where failure or rupture starts

Epicenter

the point on earths surface directly vertically above the focus

Creep

the process where blocks on either side of a break move smoothly and continuously without accumulating major stress

Foreshocks

Small micro fracture earthquakes that precede a major rock rupture

P-wave

fast compressional waves that travel through solids liquids and gases by momentarily compressing atoms and molecules (5to8km/s)

S-wave

shear waves that oscillate up and down, travel slower pass through solids but cannot travel through liquids

Body waves

combining p and s because they travel through the body of earth

Surface waves

slow waves that travel along earths surface and cause the most destruction

Modified Mercalli Intensity Scale

a subjective scale based on observed damage, witness accounts and structural impacts

Richter Magnitude Scale

an objective empirical scale created using a nomograph to measure the amplitude of energy waves

Moment Magnitude Scale

calculates total energy released based on total ruptured fault area, fault offset amount and rock strength

Liquefaction

intense shaking causes water saturated, poorly compacted sediment to lose grain to grain contact and behave like a liquid, buildings tip over and produce sand blows

Precursors

micro fractures and foreshocks, ground deformation and swelling measured via tiltmeters or GPS, changes in seismic wave velocity or electrical conductivity, water level fluctuations and sudden increases of radon gas in deep wells, unusual animal behaviour

Megathrust Earthquakes

greater than 7 and commonly around 9 magnitude

Tsunami

a set of ocean waves caused by any large erupt displacement of water

Pacific Tsunami Warning Centre (PTWC)

headquartered in Ewa beach Hawaii

1.detects major earthquakes across the pacific region

2.determine whether those earthquakes have generated a tsunami

3.provide timely warnings to participating pacific nations to minimize hazards

Seismic Gaps

locked sections that go periods of time without significant movement or earthquakes

Creeping Segments

experience a series or continuous small motions and minor earthquakes

Shaking Acceleration Based on Material

solid bedrock, consolidated sediment, unconsolidated fill and soft mud

Paleoseismology

the sub division of geophysics focused on studying ancient earthquakes to assess future seismic probabilities

Subduction Zone Volcanism

most dangerous, magma undergoes extensive modification making it silica rich, highly viscous and explosive

Volcano Percentage

90% closely associated with tectonic plate boundaries

10% from hot spots

Factors that Affect Viscosity

temperature, chemical composition, crystal content, volatiles (water)

Magma Formation

at oceanic spreading centres, divergent plates cause hot asthenosphere rock to rise close to the surface where a decrease in pressure triggers decompression melting

Ring of Fire

occurs where oceanic lithosphere subduct beneath another place, forming extensive belts like the pacific

Flux Melting

water saturated in the top layer of the sub-ducting slab is driven upward into the overlying hot asthenosphere wedge as it encounters higher heat lowering the melting temp of the rock

Magma Modification Processes

as the primary basaltic melt rises through the thick continental crust its composition is altered via, assimilation, fractional crystallization and magma mixing. Results in cooler explosive eruptions

Assimilation

magma fractures surrounding country rock, melts blocs of old granitic continental crust and incorporates their composition

Fractional Crystallization

denser, high temp mineral crystals from early and settle to the bottom of the magma chamber, removing specific elements from the remaining melt

Magma Mixing

different batches of magma combine to produce intermediate compositions

Volcanic Hazards

lava, gas, lahars, pyroclastic (ash)

Prediction Methods

seismic activity, ground tilt and deformation, gas evolution, thermal anomalies, and earth tides

Seismic Activity

short period earthquakes indicate magma chamber fracturing, while long period earthquake indicate magma is actively rising toward the surface

Ground Tilt and Deformation

measured using sensitive tilitmeters and GPS satellite networks to track the inflation and deflation cycle of swelling magma reservoirs

Gas Evolution

tracking the ratio of CO2 and SO2 as well as monitoring summit lake temperature, ph changed and colour

Thermal Anomalies

satellite infrared remote sensing detects heat anomalies as magma moves close to the surface

Earth Tides

gravitational pulls from the moon and sun can trigger minor eruptions if magma is already positioned high in the vent

Long Term Prediction and Danger Assessment

geological record, volcanism trends, volcanic explosively index

Geological Record

historical records are often incomplete, geologists rely on mapping ancient lava flows, ash deposits, and pyroclastic layers to determine long term behavioural patterns

Volcanism Trends

global volcanic activity is not on the rise apparent increases in historical graphs largely reflect better reporting and modern monitoring systems

VEI

an open ended logarithmic scale from 0 to 8 used to measure the explosively and volume of erupted tephra, where each increase represents a tenfold leap in scale

Flood Basalts

massive outpourings of basaltic lava that erupt on land from rifts fed by the tops of mantle plumes or super plumes. when they occur on oceanic curst, continental crust, or a mix of both

Mantle Boundary

around 3000 km deep

Life Threatening Hazards

global cooling and global warming

Global Cooling

dust and sulfur dioxide