ES1001 Flashcards

Question

What may be the cause of a non homogenous mineral?

Answer 1

Zonations and crystal defects

Answer 2

Biominerals - formed by a living organism usually inorganic in composition may contain organic material Amber - fossilised tree resin organic composition

Answer 3

Minerals with the same composition but different crystal structure

Answer 4

The number of direct neighbours that an atom/ion is bonded to in a crystal structure. Typically we talk about cations and their surrounding anion-neighbours.

Answer 5

the number of direct neighbours that an atom/ion is bonded to in a crystal structure. Typically we talk about cations and their surrounding anion-neighbours.

Answer 6

A space in a crystal lattice that can be occupied by an atom/ion. It is typically named by its coordination.

Answer 7

Atoms/ions in a crystal lattice can be substituted by other elements, as long as their radius is similar. Ideally, their charge would also be the same! If an element fits readily into a crystal structure, it is called compatible

Answer 8

Island silicates Consist of isolated “islands” of [SiO4] 4– tetrahedrons.

Answer 9

Group silicates Two SiO4-tetrahedrons can share one oxygen and form a group

Answer 10

Ring silicates When a SiO4-tetrahedron shares two of its oxygen corners, we can form rings

Answer 11

Chain silicates Like an unclosed ring, sharing two oxygen corners creates chains

Answer 12

Sheet silicates Sheets of Inosilicates

Answer 13

Framework silicates

Answer 14

The lithosphere is divided into 15-20 plates of varying sizes The plates move relative to each other

Answer 15

Isolated volcanic centres far away from plate boundaries Many lie at the end of a chain of extinct volcanic islands and seamounts known as a HOT SPOT TRACK Hot spot tracks are thought to be the result of plates moving over stationary plumes

Answer 16

A mineral is a crystalline, homogenous, inorganic solid with a defined chemical composition that occurs naturally

Answer 17

Their building blocks (atoms, ions, molecules) are arranged in an ordered and repeated pattern. Aka repeating he UNIT CELL

Answer 18

Mineraloid

Answer 19

Polymorphs are minerals with the same composition but different crystal structure.

Answer 20

crystallisation of a magma due to cooling effectively the same as freezing Magma cools below its liquidus, and starts to crystallise minerals. The mix of melt + minerals keeps on crystallising until it ”hits” the solidus, now all melt has solidified

Answer 21

Pure elements, metals often called “native”... usually bound by metallic (in metals) or covalent bonds

Answer 22

Minerals that have sulphur as anion.

Answer 23

Minerals with halogens (F, Cl, Br, I) as anion.

Answer 24

Minerals with oxygen and/or OH as anion.

Answer 25

… with the carbonate ion (CO3) 2- as anion.

Answer 26

… with the borate ion (BO3) as anion.

Answer 27

with the sulphate ion (SO4) 2- as anion.

Answer 28

… with the phosphate ion (PO4) 3- as anion.

Answer 29

Form 90% of Earths crust Si and O as anions

Answer 30

SiO4 tetrahedredreon 1 Si with 4 O- atoms Si4+ (+) 4o^2- makes [siO4]4^4-

Answer 31

consist of isolated “islands” of [SiO4]4– tetrahedrons. Since a mineral cannot be charged, we have to balance the quadruply-negative charge. A charge balance can be achieved by throwing cations in the mix.

Answer 32

Olivine achieves charge balance by adding two divalent cations per [SiO4]4– island. It can be either Mg2+ or Fe2+ → (Mg,Fe)2SiO4

Answer 33

Two SiO4-tetrahedrons can share one oxygen and form a group: 2 Si4+ + 7 O2- makes [Si2O7]6-

Answer 34

When a SiO4-tetrahedron shares two of its oxygen corners, we can form rings Depending on the number of rings, we get different molecular anions, with different charges… But always a multiple of Si4+ + 3 O2- → [SiO3]2-

Answer 35

Tourmaline, Beryl

Answer 36

Like an unclosed ring, sharing two oxygen corners creates chains 2 Si4+ + 6 O2- → [Si2O6]4-

Answer 37

Pyroxenes have two slightly different cation-sites in their lattice M2 (larger cation site) M1 (smaller cation site) e.g. Augite Amphiboles … are complicated and have a lot of cation-sites, but are a common mineral

Answer 38

Every SiO4-tetrahedron shares three of its corner oxygens Si4+ + 1O2- + 3*½O2- = SiO2.5 = [Si4O10]4-

Answer 39

Every SiO4-tetrahedron shares all four of its corner oxygens Si4+ + 4*½O2- = SiO2 = [SiO2]0 - No charge!

Answer 40

Quartz is a very happy chappy, doesn’t need any cations to charge balance and therefore usually is very pure. Formula: SiO2

Answer 41

Heavy element = heavy mineral (duh)

Answer 42

More atoms = more dense Like more socks = more dense suitcase Relative estimates

Answer 43

colour as a result of interaction with (sun)light (Sunlight = white light contains all wavelengths of the visible spectrum)

Answer 44

Small changes in a crystal can change the way it interacts with light. (e.g amethyst, quartz, citrine)

Answer 45

We can powder” a mineral by grinding it against a hard and rough surface, like an unglazed ceramic tile.

Answer 46

Describes whether a material allows light to pass through.

Answer 47

How a mineral reflects Just make up your own words

Answer 48

Twinning describes the intergrowth of two (or more) crystals of the same mineral through a slight change in orientation of the crystal lattice.

Answer 49

Technically the majority of transparent and translucent minerals double-refract light; CALCITE is so very slay that u can see double

Answer 50

In some minerals, absorbing (high-energy) light results in the emission of (visible) light.

Answer 51

The light emission stops when the high-energy light stops

Answer 52

The light emission can continue for some time after the excitation stops

Answer 53

Magnetite is magnetic

Answer 54

Salty stuffs Halite tastes salty. It is table salt after all. Sylvite tastes salty, too, but has a bitter aftertaste.

Answer 55

Cube Chip Matchbox Pencil Triangular prism Flattened matchbox sidey-ways Stack of cards pushed askew in two directions

Answer 56

cubic tetragonal orthorhombic hexagonal trigonal monoclinic

Answer 57

The mineralogical and structural adjustment of solid rocks to physical and chemical conditions that have been imposed at depths below the near surface zones of weathering and which differ from conditions under which the rocks in question originated.

Answer 58

The precursor rock Pressure Temp Deformation

Answer 59

Conduction (mantel) Advection (magma/hot fluid) Radioactive decay ( U, Th, K etc) Temps of 250 to >1000°C

Answer 60

Overlying rock mass Horizontal tectonic forces Pressure= fore per unit Lithostatic pressure = density x gravity x height

Answer 61

More stable at better conditions Determined by thermodynamics Thus, thermodynamics determines which collection of minerals have thelowest energy for a particular rock composition, pressure and temp

Answer 62

Due to burial Occurs with deformation Occurs over large areas Called belts Shows continental collision (therefore mountain ranges) Occurs formulations to 10s of millions of years

Answer 63

Localised heat sources Occurs around large igneous intrusions (dominated by heating n cooling) Occurs oversmaller areas Area around the intrusion is called the contact aureole Short-lived

Answer 64

Ocean floor basalts interact with hot fluids The basalt is metamorphosed

Answer 65

This occurs when you drop a huge rock from space (meteorite) onto the earth. ¨ Enormous transient pressure and temperature changes ¨ Very short lived - seconds-days ¨ Also called shock metamorphism ¨ Pressure from the impact (force per unit area) ¨ Temperature from friction

Answer 66

Related to brittle or ductile deformation in faults and shear-zones Intense deformation allows new minerals to grow ¨ Sometimes friction can provide additional heat Commonly associated with hydrothermal metamorphism

Answer 67

Composition P and T conditions Deformation

Answer 68

Eg bedding in metamorphosed sediments Eg large igneous crystals from metamorphosed igneous rocks

Answer 69

Minerals of different sizes

Answer 70

Distinct layers Aligned grains (preferred orientation) Folds

Answer 71

Layering Alternating layers of different compositions May include inherited features such as bedding Foliation A planar feature in a rock defined by the preferential orientation of mineral grains Lineation A linear feature in a rock defined by the preferential orientation of mineral grains

Answer 72

Small scale folds

Answer 73

Metamorphic rocks may have some garians that are much bigger than the average grain size

Answer 74

In FAULT related rocks they are metamorphic rocks may have some garians that are much bigger than the average grain size

Answer 75

The big grains in igneous rocks

Answer 76

The finer-grained minerals that host the porphyroblasts are collectively referred to as “matrix”

Answer 77

Individual minerals are called “matrix minerals”

Answer 78

No foliation ¨ Hornfels ¨ Granofels

Answer 79

Foliation/lineation ¨ Slate ¨ Phyllite ¨ Schist ¨ Gniess ¨ Layered or banded gneiss & Migmatite

Answer 80

Intensely foliated and sheared rocks ¨ Mylonite

Answer 81

Is those minerals that appear to co-exist stably in a rock ¨ i.e it is a list of minerals AKA Christmas rock Garnet-clinopyroxene(omphacite)-quartz Metamorphic assemblages are important for constraining metamorphic grade (Pressure & Temperature)

Answer 82

any two rocks with the same chemical composition that are metamorphosed at the same P-T conditions will contain the same minerals in the same proportion ¨ This is governed by thermodynamics ¨ We can use common rock types to define broad P-T regions based on the mineral assemblage they contain These broad P-T regions are called metamorphic facies Metamorphic facies can also be determined using other rock types such as metapelites

Answer 83

¨ Greenschist facies ¨ Amphibolite facies ¨ Granulite facies ¨ Blueschist facies ¨ Eclogite facies

Answer 84

As metamorphic rocks occur at the surface today, they must also experience a period of cooling after metamorphism ¨ We can divide the metamorphic evolution into parts based on whether T is increasing or decreasing T increasing prograde T highest peak T decreasing retrograde

Answer 85

The tall, elongated, clockwise path is characterised by deep burial and exhumation with limited heating The shorter, rounder clockwise red path is represents both substantial burial and heating

Answer 86

In contact metamorphism there is a strong temperature gradient away from the intrusion ¨ This results in changes in mineral assemblages away from the intrusion

Answer 87

Some regional metamorphic belts show a consistent change in minerals across them. ¨ The appearance of a key mineral can be mapped in as an isograd. Each metamorphic zone is separatrated by an isograd

Answer 88

The most important metamorphic environment If metamorphism occurs when continental plates collide then ancient metamorphic belts show us how and when the continents were assembled into their current configuration

Answer 89

If metamorphism occurs in subduction zone then some metamorphic belt tell us where old subduction zones were

Answer 90

Plates move apart ¨ This is where new oceans form if the process continues

Answer 91

Plates slide laterally ¨ May involve a component of extension (transtension) or compression (transpression)

Answer 92

Plates collide ¨ If one or both of the plates is oceanic then subduction occurs ¨ If both are continental then continental collision occurs

Answer 93

Building mountains Mountains represent crust/lithosphere that has been thickened ¨ Sometimes to more than double its normal thickness ¨ Thickened crust is not stable, but occurs because of tectonic forces Mountains are controlled by isostacy (the iceberg effect) ¨ The higher the mountain the thicker the crust/lithosphere

Answer 94

Alps and himalayas

Answer 95

Here we have subduction causing continental collision. There is defm & thickening due to the applied stresses

Answer 96

Two types Ocean-ocean ¨ Makes island arcs ¨ Eg Japan Ocean-continent ¨ Makes continental volcanic arcs and mountains on the continental margins ¨ Eg the Andes These may evolve into collision zones

Answer 97

Subduction involves high pressures. SO the rocks formed in subduction zones are blueschists and eclogites During burial and heating the rock experiences prograde metamorphism. The prograde reactions release water which enters the hot mantle. This water can initiate melting of the mantle: also melting of the slab can occur

Answer 98

The large input of magma heats and thickens the arc crust Arcs are very hot environments Get high T at relatively shallow depths Very high temperatures common in the lower half of arc systems High temperature-low pressure metamorphism due to magmatic heat

Answer 99

Living organisms (biota) and non-living (abiotic) factors from which they derive energy and nutrients

Answer 100

Phototrophy and Chemotrophy

Answer 101

Primary Producers: build organic matter by fixing carbon Provide most organic carbon for the biosphere Cyanobacteria

Answer 102

Cannot fix carbon to form their own organic compounds. Consumes organic compounds/primary producers

Answer 103

The biosphere is an open system with regards to energy → energy flow upwards in a food pyramid is inefficient, and relies on continued primary production

Answer 104

Mass of substance -------------------------- = residence time (10^12kg/year = GtC) of carbon Flux (in or out of)

Answer 105

A feedback is a self-perpetuating mechanism of chang

Answer 106

diminishes disequilibrium to maintain a steady state

Answer 107

enhances the effects of perturbation and drives the system further from equilibrium.

Answer 108

Terrestrial: Coal (land plants in anoxic swamps) Marine: Petroleum in shales (phytoplankton debris)

Answer 109

Carbonates; limestone, aragonite, chalk etc

Answer 110

Bicarbonate produced by weathering of both carbonates and silicates

Answer 111

Single cellular life; chemotrophs and/or non photosynthetic phototrophs Stromatolites: oldest unambiguous fossils at 3.4 Ga. Microbial mats formed of cyanobacteria (modern examples) and interleaved sediments.

Answer 112

True multicellularity has only ever arisen among the eukaryotes Results in: • Specialised cells • Increase in size • Increased morphological diversity • Sexual reproduction

Answer 113

Largely calcium carbonate plus silica and phosphate Likely as a response to predation→ modern food webs

Answer 114

Rapid diversification in body plans, particularly Bilatera • Divergence of nearly all extant phyla • Expansion in mode of life: burrowing, active swimming, pelagic

Answer 115

Rapid diversification after the P-T mass extinction Rise and dominance of the dinosaurs! + grass + flowering plants

Answer 116

Loss of dinosaurs following the K-T mass extinction Rapid diversification and dominance of mammals

Answer 117

Largest know mass extinction: occurred in two waves at ~252 Ma ~90 % of marine species and ~70 % of terrestrial vertebrates lost Siberian Traps: giant volcanic eruption coincident with the P-T extinction Dust, volcanic gases (SO2; CO2), intruded into coals → Global Warming Ocean acidification, enhanced weathering and eutrophication-induced “super”anoxia

Answer 118

Impact at Chicxulub: resulted in 180 km diameter crater. Iridium (+other PGE) spike, shocked quartz, glassy beads (ejecta spherules) Impacted anhydrite or gypsum → massive sulphur release

Answer 119

Hydroelectric power from glacially fed catchments is a major source of energy in some regions British Columbia, Canada: >85% of electricity from hydropower, and in summer 50% of water supplied by glaciers

Answer 120

Largest masses of ice, covering huge countries or continents such as Antarctica and Greenland Characterised by a slow-moving interior plateau and fast-moving edges forming outlet glaciers or ice streams 1-3km thick! Melting would cause 70 m of sea level rise

Answer 121

Large areas of floating ice in embayments or along the margins of an ocean basin, fed by ice streams from a neighbouring ice sheet e.g., Antarctic margin

Answer 122

Its the frozen part of Earth and the most susceptible to anthropogenic climate change • Important for controlling global sea level

Answer 123

Smaller accumulations of ice covering high topography or high latitude regions, characterised by radial flow outwards from the centre

Answer 124

Freezing of sea water at high latitudes Sea ice extent has been declining in recent decades due to climate change

Answer 125

Freeze-thaw activity within the upper “active layer” produces patterned ground structures such as icewedge polygons and pingos

Answer 126

regular pattern of circles / polygons formed in active layer due to cyclical freezing and thawing of water in the pore spaces and frost heaving

Answer 127

Small hills of earthcoveredice that form by expansion of pore water through the active layer as a result of pressure from expanding permafrost underneath

Answer 128

smallest – found in cirque (bowlshaped depression on side of mountain formed by glacial erosion)

Answer 129

A cirque glacier that expands outward and downward into a valley

Answer 130

When a glacier valley is partly filled by an arm of the sea, the valley is called a fjord, and the glacier is a fjord glacier Bits fall off to cause icebergs

Answer 131

Forms when valley glacier spreads out onto lowlands

Answer 132

• Air temperature falls below freezing point of salt water • Consists of freshwater as salt is excluded from ice crystals as they form • First ice to form consists of small crystalline needles: frazil ice (pure H2O) • As more crystals form they produce a viscous mixture at the ocean surface, eventually freezing together to make continuous ice cover • Cold air no longer in contact with seawater and so sea-ice growth then proceeds by addition of ice to base • Melting, sublimation removes ice from surface • But loss at surface compensated by ice crystals added to the base

Answer 133

The sea ice that persists for multiple years • In Arctic, just north of Resolute Bay: can be 3-4 m thick and decades old • In Antarctic, confined to semi-enclosed seas (Ross, Weddell): can be 5 m thick, but <5 yr old

Answer 134

sea ice cover that varies annually • Cause of variation in extent varies between Arctic and Antarctic • Arctic: warmer air temperatures is major factor in retreat of the ice margin • Antarctic: warmer ocean temperatures is major factor in retreat of the ice margin

Answer 135

Compaction by overlying snow • Air penetrates pore space and evaporation occurs at points of snowflakes • Moisture freezes between points, near center • Formation of granular snow called FIRN, intermediate stage between snow and glacial ice • Snow gradually loses interstitial air to become glacier ice

Answer 136

Top 50 m of glacier is brittle –does not flow because has relatively little weight on it • Crevasses form in top layer as glacier bends over topography (e.g., an abrupt change in slope) • Provide a conduit for meltwater from surface to get to depth in glacier through englacial channels • Meltwater can also percolate through firn layer

Answer 137

Some glaciers undergo periodic surges – rapid advances • Several kilometres per year • May be related to buildup of water at base

Answer 138

Mechanisms: • freeze-thaw at base of glacier • abrasion • plucking

Answer 139

Cover 70.8% of the Earth’s surface, Contains 97% of the Earth’s water, Have an average depth of 3.6 km.

Answer 140

Oceanic crust is denser than continental crust, The light thick continental crust floats higher on the mantle than the dense thin oceanic crust

Answer 141

Sea floor spreading creates mid-ocean ridges Subduction creates deep ocean trenches

Answer 142

Dissolved nutrients to support primary production are low in surface waters and then regenerated at depth.

Answer 143

inhibits the vertical mixing of ocean waters, preventing dissolved nutrients being transported back to the sea surface.

Answer 144

Storm mixing and tidal mixing in shelf seas breaks down seasonal stratification

Answer 145

Plate tectonics

Answer 146

Water overfills the basins and spills onto the continental crust

Answer 147

Shelf seas are important for primary production and carbon storage

Answer 148

Ocean features (seamounts, islands, plateau, trenchs)

Answer 149

Eckman Transport is the deflection of surface waters in the upper 100m of the water column, as a result of the Coriolis Effect. Surface waters are deflected 90° to the right in the northern hemisphere and 90° to the left in the southern hemisphere.

Answer 150

Winds create drag on the surface waters, setting them in motion The Coriolis effect deflects surface waters to the right in the Northern hemisphere, so oceanic gyres rotate in a clockwise direction. The opposite occurs in the Southern hemisphere.

Answer 151

The North Atlantic The Weddel Sea (Southern Ocean) Together, temperature and salinity drive the thermohaline circulation of the oceans

Answer 152

Depth profiles of temperature and salinity

Answer 153

To the right in the N Hemisphere and the left in the S Hemisphere

Answer 154

From high density waters

Answer 155

Wind stress creates small ripples in the water's surface. Now there is a pressure difference between the front and back of the wave. The front face is sheltered from the wind and experiences a lower air pressure than the back face, which faces the wind. This pressure difference pushes the wave along.

Answer 156

Water mixing (e.g. shelf sea stratificationSustainable energy sourceShipping hazardErosion/deposition of sedimentsSea level changes

Answer 157

Points with no tide

Answer 158

A flat topped volcanic mountain

Answer 159

Underwater mountain (usually volcanic)

Answer 160

Changes in shelf sea area affect primary production, ecosystem distribution, carbon transport etc. Changes in sea level affect tidal dynamics in shelf seas and the global ocean

Answer 161

The loss of the energy of tidal i.e. moon generated, waves

Answer 162

Using the and age of fossil coral reefs

Answer 163

Metals Organic chemicals Oil Contaminants of emerging concern Nutrients Plastic Noise

Answer 164

These PCBS are probably incorporated into particulate material at the ocean surface which then sinks to the ocean bottom to deliver the contaminant.

Answer 165

Rock formation created by the passing of a glacier. The passage of glacier ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the "stoss" (upstream) side of the rock and plucking on the "lee" (downstream) side

Answer 166

Striations: Produced by small rock fragments embedded in basal ice that scrape away at the underlying bedrock and produce long parallel scratch marks Chatter marks: A series of often crescent-shaped gauges chipped out of the bedrock as a glacier drags rock fragments underneath it

Answer 167

Among the most common and distinctive landforms produced by glacial erosion Bowl-shaped valley formed at glacier head Coire Sgorach on Sgurr a’ Mhaim is a classic northfacingcorrie eroded by a small cirque glacier high on the mountain face during successive glaciations of Scotland

Answer 168

Originates in a corrie, U-shaped (duh) Higher geo

Answer 169

Sharp-edged, narrow ridge of rock separating two valleys Formed when two oppositefacing glacial cirques erode headwards towards each other Also formed when two valley glaciers erode parallel Ushaped valleys Edge is sharpened by freezethaw weathering, and slope is steepened through mass wasting events and erosion Svalbard!

Answer 170

Pointed pyramidal peaks formed from cirque erosion due to multiple glaciers diverging from a central point A classic example is the Matterhorn in the Swiss/Italian Alps A Scottish example is Carn Mor Dearg

Answer 171

Tributary valley well above main valley floor: typically formed when main valley has been widened and deepened by glacial erosion, leaving the side valley abruptly cut off from main valley Steep drop-off usually creates dramatic cascading waterfalls Coire a’ Mhail and Coire Giubhsachanare both hanging valleys, with steep drops at the end into Glen Nevis below

Answer 172

freeze-thaw at base of glacier abrasion plucking

Answer 173

Sediment deposited directly by a glacier is neither sorted nor stratified Heaps of poorly sorted sediment called till are left as glaciers abate

Answer 174

Till can be then reworked by meltwater streams that transports it beyond terminus of glacier where it is deposited as outwash

Answer 175

Ridge-like accumulations of till are moraines Form as sediment is bulldozed by a glacier advancing across the land End moraines form at the terminus of a glacier, with the terminal moraine marking its furthest advance (Longyear glacier, Svalbard) Lateral moraines form at the sides (Lars, Svalbard) Medial moraines form where two glaciers join Moraines are important tools that scientists use to determine the extent of ice coverage during an ancient glaciation

Answer 176

Ice sheets mold oval hills called drumlins Drumlins are elongated parallel to the direction of ice flow Formed by glacial ice acting on underlying unconsolidated till Streamlined hills shaped beneath the ice Common in the central lowlands of Scotland, between Glasgow and Edinburgh

Answer 177

Rivers flowing beneath ice (subglacial channels) leave ridges of wellsortedsand and gravel called eskers

Answer 178

Shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters Form as a result of blocks of ice calving from glaciers becoming submerged in the sediment in outwash plain, which then melt to produce a void filled by a sediment-rich lake Landscapes marked by kettles, now typically occupied by lakes, ponds, or wetlands are clear evidence of previous glaciation

Answer 179

Kames are an irregularly shaped hill or mound comprised of piles of sand, gravel, and till that accumulates in a depression on a retreating glacier and is then deposited on the land surface with further melting of the glacier

Answer 180

The Marine Ice Sheet needs to be heavy (thick) enough to displace the water to be grounded. Ocean warming can melt the ice sheet faster than it moves out to sea thinning the Ice Sheet.

Answer 181

Positive feedback whereby the cliff face can become unstable if not supported by the buttressing effects of ice shelves Leads to rapid ice margin retreat

Answer 182

Viscous mantle flows away from depressed crust under the huge weight of a mountain chain

Answer 183

Crystals of one or more minerals bound together in a mixture

Answer 184

pumice –very frothylight-colouredcellular rock, full of interconnected gas bubbles pyroclastic rock formed from fragments of chilled magma pyroclastic = fiery fragments

Answer 185

Mid-ocean ridges Decompression melting forms mid-ocean ridge basalt (MORB) Continental rifts e.g. East Africa Over time, will become an ocean Mantle plumes e.g. Hawaii Both increased heat flow and decompression Forms ocean-island basalt (OIB)

Answer 186

Changing the chemical composition of the system If you add volatiles to Earth’s mantle (H2O, CO2) you lower its melting temperature

Answer 187

More cooling time means: -coarser -larger grains

Answer 188

A fine matrix with larger crystals

Answer 189

Huge mass of intrusive rock made of numerous plutons

Answer 190

Vertical igneous intrusions to layering

Answer 191

Horizontal igneous intrusions to layering

Answer 192

High silica content Lighter in colour

Answer 193

Low silica content Darker rocks

Answer 194

Mafic minerals crystallise First Felsic are last to Remaining melt becomes more felsic Yet it can also work in reverse

Answer 195

Melting style Opening of plate boundary above mantle creates void = mantle moves up to fill void Melting occurs via decompression

Answer 196

Melting style Hydration of mantle above subducting plate Melting occurs via volatile introduction (flux melting) Mt. Fuji

Answer 197

Source of (original) melt: crust Sediments, metamorphic rocks, igneous rocks Often melt is too viscous and deep enough in crust, so it does not escape Forms granite plutons/batholiths

Answer 198

Melting style: decompression Source of (original) melt: mantle Majority of melt is mafic Some remelting of crust produces felsic volcanoes –BIMODAL volcanism

Answer 199

Vast eruptions of basaltic lava Associated with the initial impingement of a mantle plume under a plate – often continental Can start the breakup of continents – start rifting by weakening/thinning the plate HUGE fissure eruptions of basalt

Answer 200

molten rock that moves over the ground

Answer 201

fragments blown out of a volcano

Answer 202

Expelled vapor and aerosols

Answer 203

1. Composition of melt 2. Crystal content 3. Gas content 4. Temperature

Answer 204

Temperature Increasing temperature decreases the viscosity Crystal content The present of crystals in a melt acts to increase the viscosity of a melt Gas content If the gases are dissolved, the will act as network modifiers (decrease viscosity) If the gases exsolve, they will form bubbles which act against the flow

Answer 205

Magma composition often controls gas content. • Felsic magmas have more gas; mafic magmas less. • Gases are expelled as magma rises (P drops). • Style of gas escape controls eruption violence. • Low viscosity (basalt)—easy escape; effusive eruption • High viscosity (rhyolite)—difficult escape; explosive release • Gas bubbles in rock are called vesicles.

Answer 206

• Composition, especially silica (SiO2) content. • Temperature. • Gas content. • Crystal content

Answer 207

Mafic magma – low viscosity, efficient degassing Andesitic magma – medium viscosity Rhyolitic magma – high viscosity, does not flow – forms domes

Answer 208

Mafic lava—very hot, low silica, and low viscosity • Basalt flows are often thin and fluid. • They can flow rapidly (up to 30 km per hour). • They can flow for long distances (up to several hundred km). • Most flows measure less than 10 km. • Long-distance flow facilitated by lava tubes.

Answer 209

Higher SiO2content makes andesitic lavas viscous. • Unlike basalt, they do not flow rapidly. • Instead, they mound around the vent and flow slowly. • The crust fractures into rubble, called blocky lava. • Andesitic lava flows remain close to the vent.

Answer 210

Rhyolite has the highest SiO2; is the most viscous lava. • Rhyolitic lava rarely flows. • Rather, lava plugs the vent as a lava dome. • Sometimes, lava domes are blown to smithereens.

Answer 211

Volcanoes often erupt large quantities of fragments. Volcaniclastic deposits include: • Pyroclastic debris—lava fragments (of all sizes) that freeze in air. • Preexisting rock—blasted apart by eruption. • Landslide debris—blocks that have rolled downslope. • Lahars—transported as water-rich slurries.

Answer 212

Explosive eruption: Melt, crystals and ‘country’ rock (lithic) fragments are fragmented fragmented = blasted apart …and blown from the vent

Answer 213

Andesitic or rhyolitic eruptions • More viscous magmas; more volcanic gases • Less easy to de-gas = more prone to explode • Explosive eruptions generate huge volumes of debris. • Pumice—frothy volcanic glass • Ash—fragments less than 2 mm in diameter • Pumice lapilli—angular pumice fragments • Accretionary lapilli— rounded clumps of ash forming in moist air

Answer 214

Pyroclastic fall (ash or tephra deposit) Pyroclastic flows Pyroclastic surges

Answer 215

Fallout from an eruptive column/cloud Falls like snow – mantles topography

Answer 216

Avalanches of hot ash (200oC to 450oC) that race downslope. Moving up to 300 km per hour, they incinerate all in their path. Immediately deadly; they kill everything quickly. Many historic examples: Mt. Vesuvius, Mt. Pelee, Mt. St Helens Block and ash flows - Ignimbrites welded by heat of flow

Answer 217

Like a pyroclastic flow, but denser (wetter) Very energetic eruptions Generally colder, lots of water

Answer 218

Earth receives more energy from sun (electromagnetic waves) Seasons due to Earth's xis rotation causing a tilt 30% of solar energy is affected by albedo effect

Answer 219

Earh has an approximate energy balance, energy is returned as blackbody radiation Stefano- Boltzman law: ōT⁴ W/m² (ō is a constant)

Answer 220

Atmosphere and ocean move because equator receives more energy from sun than it emits

Answer 221

To close earth's energy budget, the atmosphere and ocean need to move energy from low latitudes to high lattitudes

Answer 222

We must transport polewardsas we receive more at equator

Answer 223

Pressure decreases with altitude at a rate dependant on temperature

Answer 224

Depends on the temperature integrated between the surface and that level

Answer 225

Warm air is less dense

Answer 226

78% N2, 21% O2, 0.93% Ar and others

Answer 227

When air cannot hold any more water vapor, its saturated , to get air to condense and firm mist, fog, clods and rain, it must cool to saturation

Answer 228

We want to understand this for fundamental scientific discoveries and practical purposes

Answer 229

Comes from east

Answer 230

Comes from west

Answer 231

Comes from north

Answer 232

1. Intrusive - igneous, fine grained basalts 2. Bedded tuffs - pyroclastic deposits, fallen back into vent 3. Tuffisite, ash rich veins that never got to the surface

Answer 233

formed on or near Earth’s surface via erosion, deposition and lithification of sediment transported by water, ice and wind or precipitated out-of-solution by biotic and abiotic processes

Answer 234

clastic: composed of fragments (clasts) of pre-existing minerals/rocks (i.e. a source area or provenance) non-clastic: (bio)chemically precipitated clastic rocks and non-clastic rocks commonly occur together

Answer 235

conglomerate versus breccia: both consist of gravel-sized sediment but their grain shapes are different, rounded vs angular, respectively weathering and erosion of ‘parent’ rocks determines composition of resulting sediment intensity, duration and ‘style’ of sediment transport processes determines the texture of the sediment

Answer 236

As sediment undergoes increasing intensities and durations of weathering and transport, it begins to ‘mature’: •mafic minerals and feldspars breakdown into finer particles and clays •quartz becomes more and more enriched •sediment becomes better sorted and grains more rounded

Answer 237

Source (provenance) Weathering and transport Site of deposition Lithification occurs and the resulting sedimentary rock is classified based on its composition and texture

Answer 238

non-clastic sedimentary rocks are precipitated by organisms or abiotically temperature, salinity, water chemistry and sediment flux (needs to be low) influence precipitation chemical sediments are good indicators of environmental conditions there are numerous types of (bio)chemical sediments: coal, carbonates, evaporites and siliceous precipitates

Answer 239

Calcite Gypsum Halite Potassium

Answer 240

CaCO3 – calcite (aragonite polymorph is metastable); forms limestone*^ (Ca)Mg(CO3)2 – dolomite; forms dolostone* Fe2CO3 – siderite *can form abiotically or biotically ^fizzes with weak HCl (acid)

Answer 241

CaSO4•2(H2O) – gypsum CaSO4 – anhydrite

Answer 242

Fe2O3 – ironstone (iron oxide) SiO2 – chert (flint; opal is SiO2•nH2O)* NaCl – halite *can form abiotically or biotically

Answer 243

characterised by their allochems (grains) • bioclasts (fpieces of fossils) • ooids – small spheres • peloids – fecal pellets • intraclasts – eroded clasts and their interstitial autochem material (kinda like matrix) • lime mud or micrite (micro-crystalline calcite) • cement as coarse carbonate crystals (spar) Ooids are an allochem

Answer 244

deposition due to decreasing flow energy results in graded bedding: coarser grains at the base of beds and finer grains upwards (Reverse grading is also a thing)

Answer 245

layering <1 cm thick is termed laminated layering 1 – 10 cm is termed thin bedded layering 10 – 50 cm thick is termed medium bedded layering 50 – >100 cm thick is termed thick to very-thick bedded

Answer 246

a morphological feature formed by the interaction between a flowing fluid (water, air) and sediment on a bed bedforms inform about flow energy and transport direction

Answer 247

ripples have h <4 cm, dunes have h > 4 cm ripples and dunes inform on direction of sediment transport ripples and dunes often occur together

Answer 248

sediment is carried up the stoss side of a ripple by the flow at the crest, the flow separates from the bed and grains cascades down the lee side flow ‘reattaches’ in the trough causing erosion and that sediment is transported up the stoss-side of the next ripple the progressive cascade and migration of grains forms cross-bedding

Answer 249

when sediment is transported, it becomes organised into stable bedforms (e.g. ripples, dunes) that reflect flow ‘energy’ (velocity) acting on a particular grain size distribution generally, as flow velocity increases, the stable bedforms are: flat beds --> ripples --> dunes --> plane beds --> antidunes by recognising bedforms, and changes in bedforms through a sedimentary sequence, you can reconstruct past flow conditions and sediment transport direction

Answer 250

unidirectional flow generates asymmetric/current ripples oscillatory flow generates symmetric/wave ripples

Answer 251

wind shear generates waves waves on the surface generate a circular motion (‘orbitals’) of water molecules orbitals decrease in size downward; in shallow water these can intersect the seafloor and friction causes the circular motion to become elliptical the horizontal motion of the ellipse at the bed can move sediment and generate symmetric ripples

Answer 252

a depositional fabric in which clasts align and overlap one another, much like a run of toppled dominoes

Answer 253

these form due to gravitational instabilities via loading and by excessive shear stress

Answer 254

characteristic features of fluvial deposits: • point bars (m-scale lateral accretion surfaces) • crevasse splay sands (flat, tabular beds) • overbank or floodplain mud and fine sand • fining-upward trend from gravel in channel, sand in point bar to mud in floodplain/overbank

Answer 255

• coastal zones are the interface between marine and non-marine settings • areas where wave, tide and storm energies are dissipated • sinks for products of physical (sediment) and chemical (ions) weathering • zones of mixing between fresh and saline waters

Answer 256

• cm- to dm-thick sets of low-angle laminae • symmetric (wave) and flat-topped ripples • bioturbation (burrowing)

Answer 257

controls on patterns and characteristics of deposition in marine settings include: • physical processes such as waves, storms and tides • oceanic conditions such as bathymetry (shelf, slope, abyssal plain), salinity and water temperature (the latter two are latitudinal or ‘climatic’) • tectonic setting such as passive vs active margins

Answer 258

low to no siliciclastic flux • warm temperature (20˚- 30˚ C) • shallow water depth (<10 - 20 m) • average to high salinity (34.4 ppm)

Answer 259

The greenhouse effect The carbon cycle Forcing mechanisms and feedback Climate variation

Answer 260

Troposphere Stratosphere Outer atmosphere

Answer 261

Geological time-scales – millions of years Movement of the solar system through the galaxy ~ changes in cosmic ray flux and galactic dust Influence cloud formations - Plate tectonics – movement of continental plates Affects on ocean currents - Mountain building etc etc Affects on atmospheric circulation Weathering Presence/absence of sea ice/ice sheets at poles Albedo affects Multiple feedbacks in the system

Answer 262

Formation of Earth: 4.6 Gya 50-70 Mya later, a Mars-sized object collides with the Earth and the Moon is formed first 600 My of Earth’s history Sun was 30% fainter than at present formed with no “primary” atmosphere, but outgassing resulted in an atmosphere which was likely water vapour, CO2, ammonia, methane, hydrogen sulphide, sulphur dioxide + others no O2 at that time zircons show oceans and continental material had formed by 4.4Gya (0.1Gya after formation)

Answer 263

Impacts occurred from formation through until the Late Heavy Bombardment (about 3.9Gya) Sterilizing impacts probably occurred 6-12 times during the Hadean No real idea what the “temperature” of the planet was at this time

Answer 264

3.9 to 2.5 Gya Oldest rocks on Earth from this period Evidence for lack of Oxygen Witwatersrand gold ore (~3 Gya) Detrital Pyrite (FeS2) Was not oxidized during weathering Evolution of life: 3.7 – 3.5 Gya Evolution of methanogens (prokaryotes) [cannot survive with free oxygen] CO2 + 4 H2 → CH4 + 2 H2O Archean ends with rise in global oxygen levels Evolution of cyanobacteria (eukaryotes) – 2.8 Gya (earlier??) Tectonics different to today Higher heat flow Smaller plates (proto-continents) and many hot spots Temperatures likely warmer than today Oxygen isotopes in Archean rocks suggest oceans twice as warm as today’s tropical oceans (~50oC). This is contentious – but climate was WARM But this is odd as the Sun was less bright!

Answer 265

No Atmosphere? - The Earth should have been “frozen” for the first two billion years 3.8 Gya: Sun’s luminosity 75% of present value Yet – during the Archean liquid water was prevalent on the surface In fact the geological and palaeoclimatic record strongly suggests Earth has maintained a “moderate” climate throughout its history – BUT WITH WOBBLES The Greenhouse Effect!!! CO2 - supplied by volcanoes CH4 - Also from volcanoes - but also requires life - Methanogens!!

Answer 266

Main chemical weathering mechanism that removes atmospheric CO2 Reaction of silicate minerals (CaSiO3) with carbonic acid (H2CO3) to form clay minerals and dissolved ions CaSiO3 + H2CO3 --> CaCO3 + SiO2 + H2O Atmospheric CO2 combines with water = H2CO3 This process accounts for 80% of the CO2 removal CO2 also dissolves in sea water etc Later life – photosynthesis etc etc

Answer 267

Chemical weathering influenced by -Temperature Weathering rates double / 10oC rise -Precipitation H2O – required for hydrolysis H2O increases as temperature increases Vegetation [not relevant for Archean] Respiration in soil increases CO2 CO2 in soils 100-1000x higher than atmospheric CO2 Other factors land formation, mountain building, latitude location etc

Answer 268

If CH4 becomes more abundant than CO2, an organic haze begins to form Haze from UV photolysis (decomposition) of CH4 Creates an anti-greenhouse effect Haze absorbs sunlight in the stratosphere and radiates energy back to space E.g. Titan

Answer 269

A time of significant change Change from “small plates” to modern large plate tectonics Significant rise in O2 due to [evolution] increase of cyanobacteria (blue green algae) Photosynthesis Cyanobacteria: 2.8 Gya (possibly evolved 3.8Gya) Stromatolites Layered Cyanobacteria accretionary structures

Answer 270

Disrupted the balance Solar luminosity – low but increasing! CO2 CH4 + water vapour Increased weathering - oxidation Decrease CO2 Methanogens outcompeted (?) by cyanobacteria – decrease CH4 1st major glaciation 2.3 – 2.2 Gya It did not take much to shift the planet into a glaciation

Answer 271

Tectonic style changed Small to large plates First supercontinent Rodinia: 1 Gya – 750 Mya Bulk of land: mid-latitudes Related Grenville Orogeny

Answer 272

Neoproterozoic Snowball Earth: Cryogenian Multiple periods of severe “global” glaciation Lots of geologic evidence of low latitude glaciation Global temperatures plunged and the whole planet was encased in ice Or in “Slushball” alternative – tropics were ice free

Answer 273

Neoproterozoic Snowball Earth: Cryogenian Multiple periods of severe “global” glaciation Lots of geologic evidence of low latitude glaciation Global temperatures plunged and the whole planet was encased in ice Or in “Slushball” alternative – tropics were ice free

Answer 274

It’s the Greenhouse Effect again Volcanic activity and carbon dioxide release would NOT have ceased during Snowball periods Due to cold conditions, weathering rates were low so hydrolysis rates low and therefore little “scrubbing” of CO2 from atmosphere

Answer 275

Paleeozoic Mesozoic Cenozoic

Answer 276

Started with the Cambrian Explosion A direct response to the late Proterozoic Snowball Earth Quick evolution from “Ediacaran” fauna Initially marine Rapid evolution “empty planet” - many open ecological niches driven by predation competition for “food” resources

Answer 277

Large swings from “greenhouse” to “icehouse” conditions Understanding this long-term variability in global temperatures is not straightforward Underlying hypothesis CO2 is the main driver of global climate change Faint sun less of an issue now Myriad of feedbacks Presence/absence of continents at poles Presence/absence of ICE at poles Hydrolysis: carbonate-silicate cycle

Answer 278

540 - 490 mya CO2 ~ 4500 ppm, 16x pre-Industrial Snowball build up O2 ~ 63% of present Temp ~ 21°, 7° above present Sea level 30-90m above present No ice cover No terrestrial life Trilobites dominant in oceans (became extinct at end of Permian) Slow removal of CO2 through Hydrolysis

Answer 279

415 - 360 mya CO2 ~ 2200 ppm, 8x pre-Ind. O2 ~, 75% of present Temp ~ 20°, 6° above present Sea level 180-120m above present No ice cover Land has some plants and animals Continued removal of CO2 through Hydrolysis

Answer 280

360 - 300 mya CO2 ~ 800 ppm, 3x pre-Industrial O2 ~ 163% of present Temp ~ 14°, 0° above present Sea level 80-120m above present Land is dominated by swamps and forests Some ice cover – south pole

Answer 281

Since the “Snowballs” of the late pre-Cambrian, one of the most extensive glacial periods in earth history until “recent” glaciations of the Cenozoic Devonian to Carboniferous Super continent at poles: Pangea/Gondwana Tropical mountain range Decreasing CO2

Answer 282

300-250 mya CO2 ~ 900 ppm, 3x pre-Industrial O2 ~ 115% of present Temp ~ 16°, 2° above present Sea level >60m to <20m present Pangaea diverse climate states Cold dry at southern polar latitudes North – intense and great seasonal variation Worst extinction event in Earth’s history 95% of species disappeared

Answer 283

The boundary of the Permian and Triassic ~90% of all species died out 95% of species in oceans Marine invertebrates – worst hit! Took place over a 5-10 million year period Slow start – rapid by end Impact event (Nickel-rich Layers From impact or heavy-metal rich mantle-derived lavas) Volcanism (Flood basalt events The Siberian Traps (also another in China) ) Final complete state of Pangaea – extreme climate states Climate Change – hot or cold (or both?)

Answer 284

The emergence of the dinosaurs Predatory reptiles Amphibians living on land and in water Reef Building corals Climate and CO2 levels relatively constant

Answer 285

250 - 200 mya CO2 ~ 1750 ppm, 6x pre-Industrial O2 ~ 80% of present Temp ~ 17°, 3° above present Desert conditions prevail, leads to success of reptiles Late Triassic – emergence of dinosaurs

Answer 286

200 - 145 mya CO2 ~ 1950 ppm, 7x pre-Industrial O2 ~ 130% of present Temp ~ 16.5°, 3° above present High CO2, largest terrestrial animals ever Landscape dominated by coniferous forests and fern plains

Answer 287

145 - 65 mya CO2 ~ 1700 ppm, 6x pre-Industrial O2 ~ 150% of present Temp ~ 18°, 4° above present By end of Cretaceous CO2 levels are approaching Cenozoic levels Another extinction event which wiped out the dinosaurs Emergence of flowers and associated insects Diversification of mammals

Answer 288

Mammals increased in numbers and diversity Grasses and flowering plants expanded on land Ocean life remained relatively unchanged however The Eocene-Paleocene is the last “warm” period in Earth history Early Eocene seen as a “worst case” analogue for where today’s change in climate, as influenced by anthropogenic CO2 emissions, could go………….!!

Answer 289

55 - 35 mya CO2 ~ 385 ppm, 1.5x pre-Industrial O2 ~ 100% of present Temp ~ 19°, 5° above present BUT within this period were some significantly extreme climate states Paleocene-Eocene Thermal Maximum End of Eocene marked beginning of current icehouse climate

Answer 290

External and Internal External to climate system Orbital variations, tectonic effects, sun’s variations Internal to climate system Feedback mechanisms Ocean/atmospherics interactions Ocean conveyor belt El Nino-southern oscillation, Monsoons etc

Answer 291

- obliquity (tilt) It is this tilt that results in the planet having seasons. The larger the angle, the larger the difference between summer and winter - eccentricity How oval it is - pressession The spinning of the earth its self All whilst spinning around the sun

Answer 292

As ice sheets form, global albedo increases Results in a further temperature drop and ice expansion Expanding ice sheets result in a fall in global eustatic sea-level Makes it easier for ice to flow out from the land Further increasing albedo These mechanisms could explain some of the added cooling not explained by Milankovitch theory But still not enough

Answer 293

Acts as a pump transferring CO2 and nutrients from the surface to the deep ocean Carbon–plankton relationship Phytoplankton take up CO2, falls to ocean bottom when dead Released through oxidation – BUT deep oceans are anoxic returned to the surface when the thermohaline circulation is on If circulation slows – carbon is not returned to the surface – global cooling Changes in strength of circulation would also alter energy transfer from equator to poles – especially in N Atlantic (Gulf Stream looses energy)

Answer 294

Extra ice at poles should cause more downwelling exclusion of salt from water in ice formation Increased sea salinity – therefore denser Causing strong thermohaline circulation Colder climate means less terrestrial biological activity – therefore more atmospheric CO2 Colder climate means less moisture vapour in atmosphere less precipitation to feed glaciers Moisture vapour also a greenhouse gas

Answer 295

Ice cores High resolution palaeo archives Greenland ~130,000 yrs Antarctic ~800,000 yrs Greenland data Shows very rapid climate change

Answer 296

The last short major cold event During the transition from the last glacial into the present Holocene Occurred from 12,800 and 11,500 yrs ago General warming trend interrupted by cold reversal

Answer 297

Good quality high resolution proxy data e.g. tree-rings, ice cores, corals, speleothems, historical archives “reasonable” knowledge of the climate over this period Reasonable records of solar and volcanic forcing as input parameters in climate models Last 150 years – anthropogenic period So called “Anthropocene”

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