EOSC 210 - Midterm 1

Classification of Igneous rocks

1. Felsic 2. Intermediate 3. Mafic 4. Ultramafic

Types of Rocks

1. Igneous: formed from the colling and crystallization of magma 2. Metamorphic: formed by alteration of pre-existing igneous or sedimentary rock 3. Sedimentary: formed when weathered fragments of other rocks are buried, compressed, and cemented together or when minerals precipitate directly from solution

How rocks melt

1. Increasing temperature 2. Reducing Pressure 3. Adding volatiles (flux melting)

Anatomy of an Eruption

1. Magma forms in mantle or crust 2. Gas is dissolved in magma because of high pressures 3. Magma rises through crust due to density differences 4. Gas bubbles begin to form due to lower pressures: -Viscous magma traps gas bubbles which causes pressure to build and eruption is explosive -Non-viscous magma allows gas to escape and is non-explosive

Main factors that control metamorphic processes

1. Mineral composition of parent rock 2. Temperature at which metamorphism takes place 3. Amount and type of pressure during metamorphism 4. Types of fluids (mostly water) that are present during metamorphism 5. Amount of time available for metamorphism

Facies

A distinctive rock unit that forms under certain conditions of sedimentation reflecting a particular process or environment. Vertical and lateral differences reflect change in conditions over time and space.

Cross-cutting relationship

A principle stating that a disruption in the original rock layers such as igneous intrusions and faults is younger than the rocks they break

Lithosphere

A rigid shell made up of the uppermost part of the mantle and the crust which is broken into tectonic plates.

Formation

A series of beds that is distinct from beds above and below

Karst Topography

An area that has a land surface or topography with numerous depressions called sinkholes.

Flood Plains

Areas of deposition where streams overflow their channels and flood adjacent areas. Deposits are characterized by layers of fine-grained sediment deposited by floods, terrain is good for agriculture.

How sedimentary rocks are formed

Either formed by deposition or by precipitation from a solution which often occurs in "sedimentary basins" such as oceans

Deltas

Formed when streams enter a large body of water such as a lake or ocean and fine grained sediment is deposited from the energy change.

Principle of Biotic Succession

Fossils can help determine the age of rock units by looking at the organisms which have evolved over time

Alluvial Fans

High gradient streams enter a flat valley floor causing a loss of energy and deposition of large particles in a fan shape.

Bed

Layer of sediment or sedimentary rock with a recognizable top and bottome

Metamorphic Rocks

Made when heat, pressure, or fluids change one type of rock into another type of rock

Breccia

Pebbles with angular grains

Conglomerate

Pebbles with rounded grains

Identifying Minerals

Physical Properties: 1. Colour: not always a good diagnostic 2. Lustre: how the mineral reflects like, non-metallic or metallic 3. Streak: colour of powdered form 4. Hardness: relative resistance to scratching, softest being talc, hardest being diamond 5. Cleavage: tendency to break along weak planes 6. Fracture: the absence of cleavage Other tests include reaction to acid, magnetic properties, specific gravity, taste, radioactivity, habit

Subduction zones

Places where oceanic plates are pushed down into the upper mantle at a convergent boundary. Water is driven out to aid the melting process.

Fossils

Preserved traces of animals, plants, or organisms that are found in sedimentary rocks. Fossils help us identify and correlate sedimentary rocks at different sites.

Fluvial Processes

Processes associated with streams and rivers

Erosion

Processes by which rock, sand, and soil are transported by natural processes

Metamorphic Textures

Refers to the shape, size and arrangement of mineral grains and crystals.

Princple of Superposition

Rock layers above are younger than the rock layers below

Principle of Lateral Continuity

Rock units with similar characteristics are correlated across layers of rock

Marine Regression

Sea level falls relative to land surface, continental sediments (coarse-grained) are deposited on top of the marine (fine-grained) sediments

Marine Transgression

Sea level rises and moves towards land, marine sediments (fine-grained) are deposited on top of the continental (coarse-grained) sediments

Sediment Deposition

Sediment is deposited when the energy level of the stream decreases

Principle of Original Horizontality

Sedimentary rocks are deposited in horizontal layers due to gravity

Sediment Erosion

Sediments are eroded due to dissolution, abrasion and entrainment

Atomic properties vs. mineral properties

Some elements are native minerals however, most minerals are formed through ionic bonding of different elements

Discharge

The amount of water flowing in a stream at a particular location at an instant in time: Flow Rate (Q) = Area (A) x Average Velocity (V)

Structure of the earth

The earth is made up of the Crust, Mantle, and Core which are layers organized by least dense at the sturface to most dense in the center of the Earth.

Precambrian

The era before major life forms that comprises of 88% of geologic time. Composed of Hadean Eon, Archaean Eon and Proterozoic Eon.

Uniformitarianism

The idea that the geologic processes that operate today can be used to explain geological processes in the past

Drainage Basin

The movement of fluid from higher elevations to lower elevations through a converging network of rivers

Asthenosphere

The weak solid layer of the upper mantle on which the lithosphere "floats" since it behaves like a viscous fluid.

Plate tectonics

Theory that Earth's surface is made of rock plates that move with respect to each other due to convection cells in the mantle

Minerals

They are the building blocks of rocks. 1. Naturally Occurring 2. Inorganic 3. Solid (except mercury) 4. Crystalline Structure 5. Consistent chemical composition 6. Physical properties reflect chemical composition

Sedimentary Rocks

Weathered and eroded sediments are demented and compacted together to form this rock type.

Walter's Law

When a depositional environment migrates, sediments of one depositional environment come to lie on top of a different depositional environment.

Chemical Sedimentary Rocks

-Evaporites that come from precipitation of minerals from solution, often requires restricted basin in warm arid climate -Minerals come out of a water solution due to evaporation and are deposited at the bottom of a basin -Common evaporites are Halite and Gypsum -Also can be found in the mediterranean sea, hot springs or caves

Sedimentary Structures

-Features formed during deposition give clues to the environmental conditions at that time and place -Planar bedding -Cross lamination -Ripple marked bedding -Imbricate (overlapping) fossil shells -Cut and fill bedding

Graded Streams

-Fluvial systems will eventually establish an equilibrium condition with a longitudinal profile that is typically smooth and concave up -Caused by erosion over a long period of time -The base level of a river or steam is the lowest point to which it can flow

Causes of changes in Sea Level

-Isostatic rebound: rise of land that was under pressure from glaciers -Formation of glaciers -Sediment loading of the crust -Increased spreading ridge activity

Volcanic Hazards

-Lava flow puts people and infrastructure at risk -Tephra emissions which are small particles of volcanic rock can be emitted into the atmosphere and cause respiration problems or aircraft damage -Pyroclastic density current: hot mixture of gasses and volcanic tephra flows down the side of the volcano and destroys anything in its way -Pyroclastic fall can choke airplane engines and affect climate -Lahars are a flow of mud and debris down a channel away from a volcano that can be triggered by an eruption or severe rain event, will destroy anything within the channel

Mineral groups

-Minerals are categorized in groups based on their anions -Oxides: hematite -Sulphides: galena, pyrite -Sulphates: gypsum -Halides: fluorite, halite -Carbonates: calcite -Phosphates -Silicates: quartz, feldspar, olivine -Native minerals: gold, diamond, graphite

Felsic Magma

-Rich in elements forming feldspars and quarts -Lighter in colour -Lower in specific gravity -High viscosity -Low melting temperatures -ex. Granite, Rhyolite

Mudrock

-Rock made up of fine-grained silt and/or clay -Mudstone: does not break in layers like shale, nod bedded -Shale: thinly bedded that splits along parallel surfaces, dominated by clay -Siltstone: more silt than clay

Magma

-Rock that is hot enough to the point of being entirely molten which happens between 800˚-1300˚ depending on composition and pressure of rock -Magma is usually formed in the upper mantle and is linked to volcanic activity

Composite Volcanos

-Steep conical shape -Magma varies from felsic to mafic -Always associated with subduction at convergent plate boundaries

Sea-Floor spreading

-The process by which molten material adds new oceanic crust to the ocean floor -First hypothesized that the earth's crust moves laterally away from long volcanic active oceanic ridges -Fe rich minerals on the ocean floor aligned parallel to the earth's magnetic field -Mid-ocean ridges marked structurally weak zones were new ocean floor was generated from rising magma -Youngest rocks coicncided with mid-ocean ridges -Concluded that the continents moved after the generation of new crust at these mid-ocean ridges

Lithification

-The process that converts sediments into solid rock by compaction or cementation -Compaction: the process by which pressure reduces the volume of sediments due to a reduction in void space caused by burial -Cementation: the process by which clastic sediments are converted to rock by the precipitation of mineral cement along grains

Story of Earth's Crust

-Theory: the continents once belonged to a supercontinent called pangea -Observations: jig-saw puzzle fit of continents, alignment of geologic features and similar rock types, alignment of fossil finds, alignment of similar climates -Led to continental drift theory which had no concrete evidence

Gradient

Change in elevation over distance

Magma and Plate Tectonics

-At divergent boundaries, decompression lowers the melting point and partial melting of magma occurs, ultra mafic mantle rocks produce mafic magma -At convergent boundaries, water lowers the melting point of mantle (flux melting) and results in a range of magma compositions

Uncomformities

-Boundary between discontinuous layers of rock -usually caused by erosion

Shield Volcanos

-Broad volcanos with gently sloping sides -Composed of basalt flow and magma is always mafic -Eruptions are effusive -Found at mantle plumes (hotspots), and some are found at divergent boundaries or spreading ridges

Channel Types

-Channel types are determined by channel gradient, type of material the channel is flowing through, and the type and amount of sediment being transported -The terrain the rivers flow through impacts the type of sediment being transported -Two types: braided streams, meandering streams

Sandstone

-Composed of sand-sized particles that are cemented together -Quartz sandstone -Arkose -Lithic wacke

Types of Metamorphism

-Contact: small-scale metamorphism due to heat from adjacent rocks/magma -Regional: occur in subduction zones within continental crust, greatest at the roots of mountain ranges where there is intense heat and pressure

Mantle Convection

-Convection is the transfer of heat by motion of a fluid or fluid-like material from differences in temperature within that fluid -Mantle heat is derived from ongoing radioactive decay -When a plate subducts new material is delivered by convection into that ridge and causes movement between tectonic plates

Foliated Rocks

-Crystals arranged in parallel layers or bands -Heat and compressive forces act perpendicular to the orientation of recrystallization -In increasing grade: -Slate: fine-grained, good rock cleavage, weak -Phyllite: small platy minerals with a glossy sheen -Shist: medium-coarse grained, composed of mica inerals, breaks along foliation, most abundant metamorphic rock -Gneiss: medium-coarse grained, banded appearance, dense, strong

Clastic Sedimentary Rocks

-Detrital, grains or particles -Composed of fragments of weathered and eroded rocks -Different types of clastic rocks whose names are based on their most common particle by size

Geological time scale

-Developed in the 19th century using relative dating and fossil assemblages -Relative time: age of units relative to one another -Absolute time: specific age of a unit in years

Proving earth's structure using seismic waves

-Earthquakes generate seismic waves: P waves which are compressional waves that can travel through both solids and liquids, and S waes whih are transverse waes that only travel through solids -After an earthqueae, the P waves are observed to travel through the core where as the S waves do not -Conclusion: part of the earth must be liquid

Ripples

-Equal symmetrical ripple slopes (beach) indicate that waves that moved in two directions -Asymmetrical ripples (dune)

Unconformities

-Erosion surfaces will occur when rocks or sediments are exposed at the surface, particularly at times of low sea level -Angular unconformity: younger sediments rest upon tilted eroded surfaces -Disconformity: contact between younger and older beds is marked by a visible, irregular or uneven erosional surface -Paraconformity: beds above and below the unconformity are parallel and no erosional surface is evident -Nonconformity: develops between sedimentary rock and older igneous or metamorphic rock that has been exposed to erosion

Bowen's Reaction Series

-Experimented with cooling different rocks to observe the speed of crystallization -Two sequences: 1. Continuous crystallization: plagioclase feldspar changed from ca-rich to na-rich rocks 2. Discontinuous: mafic minerals changed from olivine -> hornblende -> biotite to felsic minerals orthoclase -> muscovtie -> quartz -Minerals with the highest melting point crystallized first and the last to crystallize were the first to melt

Divergent boundaries

-Extensional forces act on the lithospheric plates; plates move apart -Mostly found at mid-ocean ridges but also found where continents break apart (rift)

Magma composition

-Felsic, Intermediate (mix of mafic/felsic composition), or Mafic molten rock -Coarse-grained or fine-grained -Felsic magmas are more viscous, mafic magmas have a higher melting temperature

Braided Streams

-Flow in broad, shallow, channels and consists of multiple subchannels which are separated by islands or bars -Steep topography -Develop when the stream is unable to transport the available bedload continuously -Form in regions where elevation loss is high and coarse sediments are transported and then deposited as bars

Organic Sedimentary Rocks

-Formed from the remains of plants or animals -Limestone -Chalk: has a very high fossil content -Coal

Fluvial Systems over time

-Gradient, base level, discharge, sediment can change a fluvial system -The type of river channel also depends on these parameters -Rivers erode the valleys in which they flow over time

Intrusive Igneous Rocks

-Magma moves the crust in different ways by 1), Diapirism: rising blobs of lower density molten rock, then 2) Stoping: magma intrudes brittle "country rock", then 3) Melting: magma melts country rock -Plutons result from rock cooling deep in the earth's crust -Intrusive rocks follow fractures/planes of weakness: 1.Stocks or batholiths are large irregular shaped plutons 2.A sill is a flat plane, parallel to an existing layer (concordant) 3.A dyke cools straight up (discordant)

What happens to rocks when metamorphosed

-Minerals change -Crystals grow larger -Crystals realign creating foliation or bonding -Rock density increases -Low-grade vs. High-grade metamorphism has to do with increasing heat and pressure -Folation texture alters with increasing grade of metamorphism -At a certain temperature rock begins to melt and turns to igneous rock -Metaphorphic rocks always remain solid

Silicates

-Most abundant minerals in Earth's crust -Have a tetrahedral arrangement since silicon tends to produce an ion with a charge of +4 -The tetrahedra arrangement can be composed of single units (olivine), pairs, rings, chains or sheets (mica minerals) -The bonding between sheet silicates, which exist as clay-sized fragment, is weak and often swell up with water -Classified as either ferromagnesian or ferromagnesian depending on whether or not they have iron and or magnesium in their formula

Core

-Most dense part of the Earth -Consists of a fluid outer core and a solid inner core due to high pressures in addition to the high temperature -Outer core contains iron which generates the earth's magnetic field

Non-foliated Rocks

-Only heat is involved in metamorphism -Quartzie: formed from sandstone, quartz grains are fused together to create some of the strongest rocks -Marble: formed from limestone, coarse, crystalline, calcite grains are fused together and crystals grow larger

Crust

-Outermost, least dense, and thinnest layer -Oceanic Crust: high density, 10km thick, younger in age because it always subducts under continental crust -Continental Crust: low density, 35km thick, older in age

Sediment Erosion and Deposition Graph

-Particle diameter on horizontal axis -Flow velocity on verticle axis -Erosion curve: the velocity needed to get the particles moving -Settling curve: the velocity at which particles stop moving -Deposition: when a moving particle stops moving -Shows that small particles require a high velocity to begin erosion but are transported large distances

How Transportation Affects Clastic Sedimentary Rocks

-Particles can be transported as suspended loads, dissolved loads and bed loads -With increasing distance of transport... -Coarse grained -> fine grained -Angular -> abrasion -> rounded -Well graded (variety of sized rocks) -> poorly graded (all same size)

Transform boundaries

-Plates slide past each other, no production/destruction of material -Connect segments along mid-ocean ridges but can also cut through continental crust (St. Andreas plate boundary)

Convergent boundaries

-Produced by compressional forces and cause a high frequency of earthquakes -Ocean-Continent: Subduction zones where more dense ocean plate subducts under continental plate producing continental volcanic arcs (ring of fire) -Ocean-Ocean: Older plate descends beneath younger plate and produces volcanic island arcs on ocean floor -Continent-Continent: Suture zones where continental plates weld together and produce uplit creating mountain ranges

Carbonates

-React with HCl due to release of CO2 -Calcite is a carbonate which is the primary component of limestone/marble -Caronates can cause sinkholes due to erosion

Mafic Magma

-Rich in Magnesium and Iron -Darker in colour -Higher specific gravity -High melting temperatures -Low viscosity -Gabbro, Basalt

Igneous Rocks

-Rocks formed from the cooling and crystallization of molten rock -Extrusive: fine-grained, solidify near surface of earth's crust, cool quickly -Intrusive: coarse-grained, cool slowly within the earth's crust

Sediment Transport

-Saltation (bouncing) and Traction (being pushed along by the force of flow) of bedload (large particles) -Suspend load -Dissolved load transport

Sulfide Minerals

-Sulphur combines with other elements, especially metals creating them a rich source of metals such as Pb, Cu, Zn, Ni -Economic wealth from mining sulphides

Mantle

-Surrounds the core -Temperatures range from 100˚ at the upper boundary to ˚3500 degrees at the boundary with core -The mantle is a solid but behaves like a visous fluid

Quaternary Period

-The age where humans develop -We are currently living in the Holocene Epoch

Magma Composition from Volcanoes

-The explosiveness of a volcano is dependent on the viscosity and gas content of the magma -High viscosity and high gas content magma = explosive (felsic) -Low viscosity and low gas content = non-explosive (mafic) -Composition and temperature affects magma viscosity

The Rock Cycle

-The rock cycle is driven by 1) the Earth's internal heat engine which moves material around in the core and mantle, and 2) the hydrological cycle which is the movement of water, ice, and air at the surface powered by the sun -Any kind of rock can be turned into any other rock type

Parent Rock

-The rock you start with that has the same chemical composition as their parent -Examples: -Sandstone (Parent) -> Quartzite (Metamorphic) -Granite(Parent) -> Gneiss(Metamorphic) -Shale(Parent) ->Schist(Metamorphic) -Limestone(Parent)->marble(Metamorphic)

Velocity

-The time it takes a particle of water to travel a certain distance -Is dependent on position and irregularities in stream channel, and stream gradient -The velocity is greatest on the surface in the centre of the channel -Larger particles flow more than small ones

Radiometric Dating

-Using radioactive decay and half lives to date fossil and rock units -The ratio of parent (unstable radioactive isotope) to daughter (staple isotope resulting from decay) reveals the half life passed -Has helped in determining the age of the earth as 4.6 billion years old

Meandering Streams

-Wide, flat flood plains with a low gradient that follow a sinuous course -Erosion occurs in areas of high velocity (inside edge of stream) which can result in an oxbow lake

How minerals are formed

1. Cooling and crystallization of magma below or above the earth's surface 2. Precipitation out of a solution such as water 3. Chemical changes within a rock from heat and pressure produce a new mineral 4. Preciptation from biogenic activity