final!

Earth's mechanical layers in order

Earth's mechanical layers in order

lithosphere, asthenosphere, mesosphere, outer core, inner core

earth's compositional layers in order

crust, mantle, core

oceanic crust

thinner, more dense, younger crust making ocean floor; about 6-7 km thick

continental crust

portion of crust that primarily contains granite, is less dense than oceanic crust, and is 20-50 km thick

plate tectonics

theory that describes the lithosphere as a dozen large plates that move from convection in the solid mantle

what causes convection in the mantle?

heat flowing from the core and rising

What is concentrated along plate boundaries?

earthquakes, volcanoes, & topography

Topography

land formations on earth's surface that break smooth curvature (largest being continents & oceans); measured above sea level

divergent boundaries

plate boundary where new lithosphere is created from mantle becoming liquid & rising so plates move away from each other

convergent boundaries

plate boundary where lithosphere is destroyed & plates move towards each other

transform boundaries

a boundary where two plates slide past one another without creating or destroying lithosphere; special case of a strike-slip fault occurring at a plate boundary

mid-ocean ridge

occur along divergent plate boundaries; an underwater moutain chain where new ocean floor is formed

mid-ocean ridge process

hot mantle rock rises --> melt forms under lithosphere --> new lithosphere forms once magma erupts/rises to the surface as seafloor spreads

magnetic anomalies

pattern of long, narrow bands of high or low magnetic intensity (based on variation of magnetism of rocks) on seafloor parallel to the crest of a mid-ocean ridge

subduction zone

the region where an oceanic plate sinks down into the asthenosphere at a convergent boundary, usually between continental and oceanic plates

collision zones

a specific type of tectonic boundary where two or more tectonic plates are actively colliding with each other, often pushing rocks up & forming large mountain ranges

trench

long, narrow depressions on the seafloor that form at the boundary of tectonic plates where one plate is pushed, or subducts, beneath another (subduction zone)

typically formed at convergent plate boundaries

arc volcanoes process

occur at subduction zones where sinking oceanic plate melts & magma heats up & rises to surface from buoyant forces, leading to creation of volcanoes that form arc-shaped pattern along boundary

How do igneous rocks form?

cooling and crystallizing of magma or lava as it rises from buoyant forces (either intrusion or eruption)

How do metamorphic rocks form?

minerals re-equilibrate to combination of pressure, heat, & fluid conditions

extrusive igneous rock

igneous rock that forms when magma erupts & cools above the surface of Earth

intrusive igneous rock

igneous rock formed from the cooling and solidification of magma beneath Earth's surface

difference between rocks and minerals

Minerals are PURE - one substance. Crystalline structure.

Rocks are MIXTURES of minerals and other substances.

crystallization

process where atoms of a gas or liquid come together in proper arrangement or proportions to form a solid substance (crystal)

coarse-grained vs fine-grained texture

COARSE: grains are large enough to be seen w/ naked eye

FINE: grains not large enough to be seen

mineral

a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition

rock

naturally occurring solid mixture of one or more minerals or organic matter

igneous rock

rock that forms when magma cools and solidifies

sedimentary rock

a rock that forms from compressed or cemented layers of sediment

sediment

small, solid pieces of material found at Earth's surface as layers of loose particles from weathering & erosion, such as sand, silt, & organism shells

weathering

The chemical and physical processes that break down rock at Earth's surface.

erosion

The process by which wind, water, ice, or gravity transports soil and sediment from one location to another

metamorphic rock

A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions (solid-state transformation)

Where do sedimentary rocks form?

where sediment is deposited, such as ocean basins & continental margins

Where do igneous rocks form?

Mid Ocean ridges, volcanic arcs at subduction zones, hotspots

Where do metamorphic rocks form?

Deep beneath the Earth's surface in convergent margins, divergent margins, or collision zones

hotspots

places where molten material from the mantle reach the lithosphere

what two features classify igneous rocks?

texture and chemical/mineral composition

Felsic rocks

poor in iron and magnesium & rich in felsic minerals (silica & feldspar) as well as Na and K; have less pressure & more water content; tend to be lighter in color; lowest melting point (650-800 °C)

Mafic rocks

poor in silica, rich in magnesium, iron, & calcium; have more pressure & less water content; darker color; highest melting temp (1000 to 1200 °C)

what are the three types of melting?

decompression, volatile flux, & thermal (heat transfer) melting

magma chambers

large pools of molten rock that form in lithosphere as rising magmas melt & push aside surrounding solid rock

three locations of magmatism

mid ocean ridges, subduction zones (fluid-flux melting), & hotspots (thermal melting)

what is meant by extrusive/intrusive equivalent?

Extrusive & intrusive igneous rocks form 2 parallel sets of igneous rocks → identical in composition & only differed in texture

Intermediate igneous rocks

midway between felsic and mafic rocks; neither rich nor poor in silica; midway in Na, K, Fe, Mg, Ca content; melting point (800 - 1000 °C)

decompression melting

melting that occurs from a decrease in pressure w/o any additional heat

volatile flux melting

melting caused by adding volatiles (such as water); not changing pressure or temp but adding water causes rock to melt at different conditions

thermal melting

melting caused by increase of temp; occurs at hotspots

partial melt

the process by which a fraction of a rock has melted at a given temp since different minerals in rock melt at different temps (cold to hot); felsic rocks melt first

Compositions of melt & solid residue left behind differ from both each other and the starting rock

magmatic differentiation

rocks of varying composition can arise from uniform parent magma, as different minerals crystallize at different temperatures

fractional crystallization

process where liquid melt in rocks are separated from crystals formed in cooling magma (hot to cold)

• creates range of mafic to felsic rocks

concordant intrusion

an igneous intrusion whose boundaries lie parallel to layers of bedded country rock

mantle plumes

a localized column of hot magma rising by convection in the mantle that causes volcanic activity in hot spots

Earth's interior temperature ______ with depth

increases

Earth's interior pressure ______ with depth

increases

Intrusive igneous rocks

rock formed from the slower cooling and solidification of magma beneath Earth's surface when rocks force their way into surrounding rock; large, interlocking composition

Extrusive igneous rocks

rock that forms from the rapid cooling and solidification of lava at Earth's surface; fine-grained texture or glassy appearance

What does the temp a rock melts at DEPEND on?

other than temp, depends on mineral composition, pressure, & absence/presence of volatiles

magma composition - hottest to coldest

• HOTTEST: Ultramafic magma (low silica)

• Mafic magma (basaltic)

• Intermediate magma (andesitic)

• COLDEST: Felsic magma (rhyolitic; high silica)

plagioclase feldspar

continuous minerals in igneous rocks where calcium (mafic) & sodium (felsic) substitute for one another in same crystal structure

Siliciclastic sedimentary rocks

• Formed from clasts of primarily silicate sediments

• Classified by SIZE & MATERIAL

physical weathering

takes place when solid rock is fragmented by mechanical processes, such as freezing & thawing, that do not change its chemical composition

chemical weathering

processes by which minerals in a rock are chemically altered or dissolved

types of currents

• Strong currents = faster than 50 cm/s, carry gravel along w/ abundant supply of smaller particles

• Moderate currents = between 20-50 cm/s, lay down sand beds

• Weak currents = slower than 20 cm/s, carry muds composed of finest clastic particles

What is the driving force of chemical & biological sedimentation?

precipitation

Currents that move across Earth’s surface generally flow _______ & accumulate in ______

1. downhill

2. depressions in Earth’s crust

subsidence

broad area of crust sinks (subsides) relative to surrounding crust and forms depressions, mainly driven by plate tectonics

continental shelf

the edge of a continent that lies under the ocean

Carbonate

Sedimentary environments where sediments are rich in carbonate minerals

Evaporite

Sedimentary environments where sediments result from the evaporation of water

Siliceous

Sedimentary environments characterized by sediments rich in silica.

Wetland

Sedimentary environments associated with wetlands, often involving organic-rich sediments

Show how minerals are classified by grain type (3 groups)

• Coarse-grained: gravel and conglomerate

• Medium-grained: sand and sandstone

• Fine-grained: silt and siltstone; mud, mudstone, and shale; clay and claystone

gravel and conglomerate

• Gravel = coarsest siliciclastic sediment, consisting of particles larger than 2 mm in diameter & including pebbles, cobbles, & boulders

• Conglomerate = lithified equivalent of gravel

sand and sandstone

• Sand = medium-sized particles (0.62 - 2mm in diameter) that can be seen by naked eye & moved by moderate currents

• Sandstone = lithified equivalent to sand

silt and siltstone

• Silt = siliciclastic sediment w/ grains between 0.0039 - 0.062 mm in diameter

• Siltstone = lithified equivalent to silt

mud, mudstone, and shale

• Mud = siliciclastic sediment containing water where most particles are less than 0.062 mm in diameter deposited by rivers & tides

• Mudstone = one equivalent of mud that are blocky & show poor or no bedding

• Shale = one lithified equivalent of mud composed of silt and significant component of clay, causing them to break readily along bedding planes

clay and claystones

• Clay = most abundant component of fine-grained sediments & sedimentary rocks, with particles that are less than 0.0039 mm in diameter

• Claystones = rocks made up exclusively of clay-sized particles

What are carbonate sediments? Give an example of a rock it would form.

sediment formed from accumulation of carbonate materials directly or indirectly precipitated by marine organisms

• EX: Limestone = dominant biological sedimentary rock lithified from carbonate sediments & composed mainly of calcite

What are evaporite sediments? Break them down further into their 2 subcategories.

chemical sediment that is precipitated from evaporating seawater or lake water

• Marine evaporites = formed by seawater

• Non Marine evaporites = form in arid-region lakes

Energy (force of materials moving) of environment is critical for what?

control on particle size

• Transport mechanisms = ice, air, water

High energy environment

can carry large grains like cobbles, gravel, & coarse sands

• Glaciers, mountain rivers, reefs, beaches

Intermediate energy environment

can carry grains such as sand & mud

• Meandering rivers, delta, continental shelf & slope, deserts (dunes)

Low energy environment

carry fine sand, silt, & mud

• River floodplains, tidal flats, continental shelf & slope, deep sea, deep lakes

Describe the 3 types of sedimentary rock and what they are classified by, also including examples of each rock.

1. Siliciclastic = forms from clasts of primarily silicate sediments

• Classified by grain size & material of particles

• sandstone

2. Biological = primary material is precipitated by microscopic organisms

• classified by type of organic material & texture

• chert, limestone

3. Chemical = precipitate from evaporation of water & deposited locally

• Classified by chemical composition

• Gypsum, Halite, Anhydrite

Where are all 3 types of sedimentary rocks formed?

passive continental margins, where there is an edge of a continent that is not a boundary

how do passive continental margins form?

Form by subsidence

• Cooling of lithosphere after rifting

• Weight of sediment pushes down surface of lithosphere

Transgression

landward movement of shoreline due to rising sea level or sinking of lithosphere (sea moves out more)

• depositional environments move inland, leaving sedimentary deposits behind

Regression

seaward movement of shoreline due to falling sea level or rising continent (sea goes out)

• depositional environments move seaward, forming layers of sediment

3 main factors in metamorphism

Change temp

Change pressure

• Confining pressure (pressure due to weight of rocks)

• Tectonic stress (applied force in particular direction)

Change fluid conditions

• release/transport elements by fluids

Net results of metamorphism

Low P minerals transform into high P minerals; new minerals form with long axes parallel to minimum stress

Types of metamorphic changes

Change mineral composition

Change in texture

• Change mineral type

• Develop fabric (preferred orientation of minerals)

  • Foliation

  • Cleavage

  • Schistosity

Foliation

parallel alignment of platy minerals (such as mica or chlorite) in distinct layers or sheets from intense P and/or T

Cleavage (metamorphic)

tendency of certain minerals to break along foliation

Schistosity

type of foliation w/ metamorphic materials in wavy/wrinkled layers, where minerals grow in direction of minimum applied stress (since it is easiest)

When it comes to metamorphic changes, in general…

increasing _____ = increasing ______ size = enhanced ______ & _______ _______

• grade

• grain

• schistosity

• compositional banding

What are the 3 metamorphic grades in terms of pressure and temperature? What type of mineral is a cause of these grades?

1. Low grade - low P, low T

2. Intermediate - low P, high T OR high P, low T

3. High grade - high P, high T

Index minerals are diagnostic of metamorphic grade

The set of minerals in a metamorphic facies depends on…

the protolith (original rock type; igneous or sedimentary)

metamorphic minerals that grow depend on ______ composition

parent composition

• different parents under same P-T conditions = different minerals!

actualism

physical processes that exist now also operated similarly in the past