ES2001 Vocab

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Geodynamics

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191 Terms

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Geodynamics

The study of the large scale evolution of the solid earth

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Plate Tectonics

Broad area of study of how planets behave

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Geoid

A reference surface representing the elevations. Worldwide, at which gravitational potential energy is the same

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Plate

One of about 20 distinct pieces of the relatively rigid lithosphere

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Divergent

Plates move apart Oceans form if process continues

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Transform

Plates slide laterally; May involve a component of extension

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Convergent

Plates collide If one or both plates are oceanic then subduction occur If both are continental then continental collision occur

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Isostatic Equilibrium

The condition that exists when the buoyancy force pushing lithosphere up equals the gravitational force pulling lithosphere down

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Pratt theory

Blocks of some mass are different densities Ocean vs continental crust explanation

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Airy theory

Blocks of same density different masses Himalayas are high and Aus is close to sea level

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Mid-Ocean Ridge

A k-km-high submarine mountain belt that forms along a divergent oceanic plate boundary

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Rift

The process by which continental lithosphere stretches horizontally and thins vertically

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Transform Boundaries

A boundary at which one lithosphere plate slops laterally past one another

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Transform Fault

A fault marking a transform plate boundary; along mid-ocean ridges, transform faults are the actively slipping segment of a fracture zone between two ridge systems

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Transpression

Makes narrow linear mountain belts

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Transtension

Makes narrow linear basins

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Subduction

The process by which one oceanic plate bends and sinks down into the asthenosphere beneath another plate

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Subduction Zone

The region along a convergent boundary where one plate sinks beneath another

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The Wilson Cycle

The balance of creation and destruction of tectonic plates

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Metasomatism

The process by which a rock’s overall chemical composition changes during metamorphism because of reactions with hot water that bring in or remove elements

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Subduction metamorphism

Metamorphism occurs both in the subduction zone and in the arc and back arc environment The P and T conditions are very different in each part

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Obduction

The sideways and upwards movement of the edge of a crustal plate over the margin of an adjacent plate. Tectonic failure

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Ophiolite

A slice of oceanic crust that has been thrust onto continental crust

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Orogen(esis)

Mountain building process. Mountain belts

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Shield

An older, interior region of a continent. North America has the Canadian

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Supercontinent

A very large continent formed by the suturing together of smaller continents

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Facies

A group of rocks and primary structures indicative of a given depositional environment Texture, Structures, Bedding Geometry, Bedding Contacts, Fossils, Colour

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Cross bed

Internal laminations in a bed, inclined at an angle to the main bedding; cross beds are a relict of the slip face of dunes or ripples

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Planar

Occurs when crest of the dune or ripple is a straight line which are called 2D Ripples

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Trough

Occurs when cross beds have a curvy or non parallel forest leads to little scoops in the rock. The crest of the dune is not a straight line

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Newtons 1st law

Inertia (object will remain at rest or in uniform motion unless acted on by an external force)

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Newtons 2nd law

Force = mass x acceleration

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Newton’s 3rd Law – equal and opposite reactions

When a grain reaches a constant settling velocity, only drag on the grain balances the net force between gravity and buoyancy

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Archimedes’ principle of levers and torque

Work = force x length of lever (moment) arm = FL

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Sediment Entertainment

When grains start to move

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Suspended load

Grains remain in water column until conditions change

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Bed load

Large particles such as sand, pebbles, or cobbles, that bounce or along a stream bed

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Traction transport

The geologic process whereby a current transports larger, heavier rocks by rolling or sliding them along the bottom

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Saltation

The movement of a sediment in which grains bounce along their substrate, knocking other grains to the water column (or air) in the process

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40

Benoulli’s Principle

Within a horizontal flow of fluid, points of higher fluid speed will have less pressure than points of slower fluid speed, i.e. within a horizontal water pipe that changes diameter, regions where the water is moving fast will be under less pressure than regions where the water is moving slow. Just another way of saying that water will speed up if there;s more pressure behind it than in front of it.

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Buoyant force

Buoyancy is an opposite and equal force to gravity if a grain is not in motion (but driven by the fluid density, not grain density)

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Stokes Law

An expression describing the resis5ng force on a par^cle moving through a viscous fluid and showing that a maximum velocity is reached in such cases, e.g. for an object falling under gravity through a fluid.

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Terminal velocity

The highest velocity attainable by an object as it falls through a fluid (air is the most common example). It occurs when the sum of the drag force (Fd) and the buoyancy is equal to the downward force of gravity (FG) acting on the object.

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Tides

Motion of water around the Earth due to gravitational forces set up by the alignment of the sun, Earth and moon Highest high and lowest low water – spring tides (max. range) Lowest high and highest low water – neap tides (min. range)

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Transitional waves

When water depth is
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46

Transgression

flooding due to sea-level rise. Sediment belts shift landward; strata ‘deepen’ upward.

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Retrogradation

is the landward change in position of the front of a river delta with time.

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Regression

exposure due to sea level fall. Depositional belts shift seaward; strata ‘shallow’ upward. tied to erosion; less likely to be preserved.

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Progradation

the growth of a river delta farther out into the sea over time.

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Walther’s Law

Any vertical progression of facies is the result of a succession of depositional environments that are laterally juxtaposed to each other.

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Hadean

4.5 Ga (formation of the earth) to 3.8 Ga (sometimes 4.0 Ga; the oldest preserved rock)

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Late heavy bombardment (LHB)

~3.8-3.9 Ga? Created the majority of the moon’s craters

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Zircon (ZrSiO4)

the oldest remaining mineral on Earth. Grains over 4 billion years old can reveal information about Hadean surface conditions Rocks can’t be used to determine if habitable conditions existed. Zircon is very resistant to melting and withstand many impaces

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System component

reservoir of matter or energy, system attribute, or as subsystem

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Positive coupling

a change in one component produces a change in the same direction in the linked component

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Negative coupling

a change in one component produces a change in the opposite direction in the linked component

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Archean-Proterozoic Boundary

2.5Ga Appearance of modern-style cover sequences (unconformity-bound sedimentary packages on continental crust) Sediments are being deposited over the cover sequence

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Shaw Granitoid

(~3Ga) In AUS Weathered old rock that has been metamorphosed

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Stolzenberg Pluton

(3.4-3.2 Ga) Multiple generations of magmatism

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Greenstone belts

pillow upon pillow basalt…

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Greenstone

mostly stones that are greenish and form belt shapes During low grade metamorphism basalt turns into a green colour Basalts are really abundant during the Archean

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Komatiite

An Archean oddity Ultramafic extrusive rock. Commonly displays spinifex texture of large acicular olivine and pyroxene crystals Likely indicates very hot mantle melting conditions Its rare because it comes out to the surface and solidifies It was only abundant in the Archean Theory is that the mantle was much hotter in the ArcheanThe elements didn’t separate which created cement basically

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63

Hydrothermal Barite (BaSO4)

Dark colour of otherwise white barite crystals reflects inclusions of fluids, minor organic matter, and pyrite Contains sulphur gas which makes it dark

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Cross bedding in sandstone between pillow basalts

(3.4 Ga) Evidence of erosion and sediment transport Less quartz rich and less mature sediment Sedimentary process occurred similar to today

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Stromatolites

microbial structures, orientated towards the Sun Microbial mats create a sticky organic film Photosynthesis locally removes CO2 and increases the pH

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Strelley Pool formation

Stromatolite reef at 3.4 Ga Steep angle cones interpreted as evidence of sticky microbial mats that trapped sediment grains

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67

The faint young sun paradox

The sun was dimmer in the Archean and has become hotter over timeThe modern greenhouse effect would not have been strong enough to keep the Earth above the freezing point of liquid water until about 2 Ga More greenhouse gases were needed to explain evidence of liquid water

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68

Macropalaeontology

Invertebrate & Vertebrate

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Micropalaeontology

e.g. forams, diatoms

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70

Palynology

pollen, spores

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71

Palaeobotany

fossil plants

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72

Ichnology

trace fossils, e.g. burrows, tracks

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Palaeoecolgy

interactions between fossil organisms and their environments

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74

Phylogeny

Evolutionary relationships between biological taxa

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Phylogenetic Trees

Phylogenetic trees may be used to investigate the sequence & timing of origination of particular features of organisms

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Crown group

defined by a shared common ancestor of a clade, as well as all the descendents of the common ancestor

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Stem group

a grouping of extinct species related to, but basal to (on the stem), the crown group

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Clade

a group that includes an ancestor (node) and all of its descendants (all shallower nodes and terminal taxa that descend from that node) on a phylogenetic tree

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Sister taxa/sister groups

Parts of terminal taxa/clades that branch from a common node

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80

Morphology

The study of animal from. In palaeontology it refers to the study of bone anatomy and function, and the muscle reconstruction from evidence of muscle attachments on bone. May also be used to infer behaviour which is usually bases on anatomy and behavioural biology of modern day animals

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81

Tomography

Most widely-used method to visualise fossils in 3D is X-Ray computed tomography. This allows non destructive, high resolution reconstruction of the whole fossil

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Taphonomy

The process from death to fossilisation

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Decay experiments

does decay introduce bias into the fossil record? Soft vs. hard tissue

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Melanosomes

Contain melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for colour and photoprotection in animal cells and tissues

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The Cambrian

541-485Ma

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Cambrian ~515 Ma

Big diversification in animal taxa Swimming Predation Increased body size Defence Massive radiation in Phyla with bilateral symmetry

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Burrowing Biomineralization

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The Cambrian Explosion

Huge diversification of animal life Appearance of all major animal body plans Big changes in mode of life (burrowing) Marked predator/prey relationships

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Burgess Shale

~508 Ma Discovered by Charles Walcott in 1909, in British Columbia, Canada soft - tissue preserved as carbonaceous remains

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What caused the Cambrian Explosion?

Red Queen Hypothesis

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Diversification driven by biological predator-prey relationships (biotic)

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What caused the Cambrian Explosion?

The Court Jester Hypothesis Diversification drive by the physical environment (abiotic)

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Trilobites (arthropoda; Trilobita)

First appearance 521 Ma, lasted until ~252 Ma (lasted ~270 Myr)

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Bryozoa

Filter feeding zoids that form sessile colonies with a shared exoskeleton

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GOBE

Great Ordovician Biodiversification Event

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Planktonic Revolution

Late Cambrian-Early Ordovician Marks the arrival of fossil planktonic organisms into the fossil record Explosion in diversity of phytoplankton→basis of marine food chain Followed by various zooplankton

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Graptolites

Colonial animals that lived in an interconnected system of tubes; skeleton made of collagen. Incredibly useful for relative dating and biostratigraphy throughout the Ordovician to the mid Devonian. Morphological Change Sessile to planktonic mode of life Single type thecae (Graptoloidea) Biserial stipes

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What caused the GOBE?

Ordovician marked by a warm global climate → subsequent high sea levels result in flooding of continents and expanded shelf habitats Biotic factors → primary significance at the local, community level scale Abiotic factors → likely to have been of importance at the larger palaeocontinental scale orogenesis; tectonics; volcanic activity Palaeogeography increased tectonic activity resulted in numerous and widely separated continental platforms

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99

Requirements for modern reefs

dominated by aragonite Scleractinian corals → corals can be fussy! Dominantly tropical waters Well-lit within the photic zone

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Clear water symbiont photosynthesis; suspended sediments clog corallites

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