History of Geology

Mid 1600s

-believed the eart was created Oct. 22, 4004 BC

-James Ussher

-Archbishop of Armagh, Ireland

-came up with the idea that the earth was created oct. 22 4004 bc based on old testament events

-the belief that the earth was shaped primarly by huge catastrophes

"young earth"

-a scottish physician

-considered the father of modern geology

-"the present is the key to the past"

-believed in a "old earth"

Uniformitarianism

4.6 Billion years old

Nebular Hypothesis

the idea that the sun and plants were formed from a single blob of gas and dust (solar nebula)

the process is believed to have started about 5 billion years ago and is thought to still be happening today

(in order...top to bottom)

-Crust (continental and oceanic)

-Mantle 

-Core

-thick

-low density silicate minerals

-thin

-intermediate density silicate minerals

(in order from top to bottom)

-Lithosphere

-Asthenosphere

-Mesosphere

-Outer Core

-Inner Core

-consists of the crust plus the upper mantle

-cold and rigid

-behaves like "normal" rock

-consists of the mantle below the lithosphere

-hot, soft, and capable of slow flow

-lower mantle

-more rigid than the asthenosphere

-outer: molten (liquid metal)

-inner: solid metal

Observation

-facts; data

-foundations of scientific inquiry

-a well tested; widely accepted view that best explains a wide ranging set of observations

-the goal of science is to derive theories

-theories explain how the world works

-the earth's lithosphere is divided into discrete plates that are in motion relative to eachother

-interactions between plates are main cause of volcanism, earthquakes, mountain building, and many other geologic phenomena

-plate motion driven by mantle convection 

-convergent

-divergent

-transform

-nucleus is the central core of the atom

-has an equal number of protons and electrons

-atoms bond together to form compounds

-controlled by interactions between electrons

-naturally occuring

-inorganic

-crystalline solid

-set chemical composition that varies only within certain limits

-quartz, diamond, graphite, salt

-NOT sugar, mercury, dietary "minerals"

-metals

-fertilizer

-industrial/construction materials

-silicates

-carbonates

-oxides

-evaporites

-based on silicon-oxygen tetrahedron
 -Si-O bond is relatively strong

-the linking of Si-O tetrahedra to each other determines mineral properties

-these are very common, widespread minerals

-quartz

 -feldspar

-mica

-garnet

-based on the carbonate ion (CO₃^2-)

-commonly form in the sea

-Calcite (CaCo₃)

-Dolomite (CaMg(CO₃)²)

-metal/sulfur combination

-important metal ores

-galena (PbS)

-pyrite (FeS₂)

-sphalerite (ZnS)

-metal/oxygen combination

-most widespread as weathering products of other minerals

-hematite (Fe₂O₃)

-limonite (FeOOH)

-magnetite (Fe₃O₄)

-formed by evaporation of mineral-laden water (seawater or desert salt lakes)

-very soluble in water

Examples of Evaporites

-halite (NaCl)

-gypsum (CaSO₄2H₂O)

-mantle

-ocean floor

-continents (??)

-soil

-quartz

-feldspar (plagioclase and orthoclase)

-mica (muscovite and biotite)

-amphibole/hornblende

-pyroxene (augite)

-olivine

-garnet

-isolated tetrahedra

-chains

-double chains

-2-D sheets

-3-D networks

-SiO₄ units glued together by other atoms

-olivine

-garnet

-each Si atom shares one oxygen with an adjacent Si atom

-chains glued together with other atoms

-pyroxene

-augite

-pairs of chains cross linked by shared oxygen atoms to form double chains

-double chains glued together by other atoms

-amphibole

-hornblende

-each chain linked to chains on either side to form continuous sheet of Si-O tetrahedra

-sheets glued together with other atoms

-mica (biotite and muscovite)

-clay (kaolinite)

-each Si shares all oxygens with adjacent Si atoms

-other atoms stuffed into gaps where they fit

-feldspar (orthoclase, plagioclase)

-quartz

-dark colored

-contain Fe and Mg

-dense (grav 3.2-3.6)

-olivine, pyroxene, amphibole, biotite

-light colored

-no Fe and Mg

-less dense (gravity 2.7)

-muscovite, feldpar, quartz, clays

minerals: quartz (biotite, muscovite, amphibole), feldspars, orthoclase, plagioclase

rocks: granite 

minerals: plagioclase, pyroxene group, olivine

rocks: basalt 

Composition of Mantle

-minerals: pyroxene group, olivine

rock: peridotite 

-oxygen 46.6%

-silicon 27.7

-aluminum 8.1

-iron 5

-calcium 3.6

-sodium 2.8

-potassium 2.6

-magnesium 2.1

-all others 1.5 

-formed by cooling and crystillization of molten rocks

-are made of interlocking network of mineral crystals

ex. granite 

The earth's temperature increases with depth so...

(1) forcing a crystal rock to great depths will cause partial melting

(2) an upwelling of hot material will also cause melting 

molten rock extruded at surface

*as pressure is released inside the earth, water vapor and gasses are released... this outgassing can be violent and cause eruptions 

molten rock beneath the earth's surface

*molten minerals

*gasses

-water vapor

-carbon dioxide

-sulfur compounds

-nitrogen compounds 

intrusive (volcanic)

and

extrusive (platonic) 

-small crystals

-formed when lava is released from volcanoes and cools at the earth's surface

-rapid cooling which is why they have small crystals 

-formed when magma cools deep underground

-it is slow cooly and because of this has large crystals 

-glassy

-aphanitic

-phaneritic

-pegmatic 

-porphyritic 

the crystals are too small to see

-this is typical of extrusive (volcanic) rock 

-the crystals are large enough to see

-typical of intrusive (plutonic) rocks 

extremely large crystals

these rocks are referred to as pegmatites 

-large crystals (phenocrysts) in a matrix of smaller crystals (groundmass)

-this rock is called a porphry 

ground mass (the matrix of smaller crystals)

and

phenocrysts (the large crystals) 

-when airborne particles solidify then pile up on the ground

-there are many different kinds and ash deposits are normal 

a chart that describes the order that minerals crystallize out of molten rock

it shows how certain minerals are associated with other minerals 

-rocks with abundant feldspar and quartz

-ex. granite and rhyolite 

-these are rich in iron and magnesium

-ex. gabbro and basalt 

-high temperature

-low silica

-medium viscosity

-quiescent eruption style

-found in ocean basins

-medium temperature

-medium silica

-medium viscosity

-violent eruption style

-found in continental margins 

-has a range of composition

-may be viscous or runny 

-blown out by escaping gasses

-solidifies mid air

-dust to car sized blobs

-commonly vesicular 

-shield volcano

-composite cone/ stratovolcano

-cinder cone 

-largest volcanoes

-mauna Loa 30,000 ft. from base to summit

-low-angle slope, broad, round domes

-ex. hawaiian islands, iceland

-basalt (low viscosity lava)

-relatively non violent 

-also called stratovolcanoes

-alternating layers; volcanic ash/lava flows

-classic volcano (steep sided and tall)

-ex. Mt. St. Helens, Mt. Fuji, Mt. Rainer

-intermediate composition (andesite)

-violent, very dangerous eruptions 

-puny (a few hundred to 1000 ft. tall)

-made of pyroclastic debris (cinders)

-commonly formed in last phase of larger eruption

-ex. Capulin Volcano and Sunset Crater 

(1) Cinder Cone

(2) Stratovolcano

(3) Shield Volcano 

-large eruptions of pyroclastic material

-common for felsic magmas

ex. yellowstone area 

-huge outpourings of basaltic lava

-erupt from fissures; there is no central volcano

-can cover 1,000 sq. miles

-ex. Columbia Plateau, Snake River Plain 

(1) Explosions ---> landslides, tsunami

 (2) Ashfall ---> suffocation, building collapse

ex. Pompeii

 (3) Lava Flows ---> start fires, destroty property, destroy roads

ex. Congo 

(4) Nuee Ardent (glowing avalanche) flows at 60-100mph and is 800-1500 deg F

(5) Lahar ---> mudflow on volcano can travel miles down river 

subduction zone

and

mid-ocean ridge 

- tabular (planar) intrusions

-blob shaped intrusions 

-dike- cuts across sedimentary layers

-sill- parallels to layering 

-batholith- worst intrusion and is commonly granite

-stock- small batholith

-laccolith- a dome shaped intrusion that forces its way between sedimentary layers 

rocks formed from the weathering products of other rocks

ex. sandstone (made from sand)

shale (made from mud)

 limestone (made of calcite)

rock salt (made of halite)

clay and dissolved minerals like...

Calcium, magnesium, Iron, Sodium 

the notes say I.p.o.q.

noooo idea what this means :)  

1. weather a pre-existing rock

2. erosion and transport

3. deposition

4. lithification (compactation and cementation) 

-conglomerate (made of sand and pebbles)

-sandstone (made of sand)

-shale (made of mud) 

inorganic: evaporation

organic: mineral precipitation aided by living organisms

Particle size of detritol sedimentary rocks

<2mm 

sediment name- gravel

rock name- conglomerate 

Particle size of detrital sedimentary rocks

1/16- 2mm 

sediment name- sand

rock name- sandstone 

Particle size of detrital sedimentary rocks

<1/16mm 

sediment name- mud

rock name- shale or mudstone 

composed mostly of quartz

"arkose": contains significant feldspar and other minerals

has a grain sorting or grain rounding texture 

made of sand and pebbles (looks like concrete)

indicates a desposition in a very high energy environment... like mountain stream, raging flood, pebble beach 

-limestone

-dolostone

-chert (flint, jasper, agate)

-evaporites

-coal 

-10% of sedimentary rocks

-composed of calcite

-most precipitated by marine organisms; forms in the sea

-some inorganic (cave deposits) 

-composed of mineral dolomite

-most formed through alteration of limestone 

-micro-crystalline quartz

-composed of siliceous shells of marine microorganisms 

-rock salt; halite

-rock gypsum 

-pickled plant remains behind

-forms in oxygen poor environments

-often found in swamps 

Depositional Environment

High Energy 

-fast water

-deposits wil contain lots of large particles

ex. mountain stream, beach with large waves 

Depositional Environment

Low Energy 

-slow water movement

-deposits will contain mostly very small particles (mud)

-ex. lake bottom, swamp, sluggish river 

-all quartz: it had a lengthy sediment transport

-lots of feldspar, etc: minimal sediment transport 

-well sorted: lengthy sediment transport

-poorly sorted: minimal sediment transport 

-well rounded: lengthy sediment transport

-poorly rounded: minimal sediment transport 

have well sorted grains well rounded grains....  almost all quartz

ex. a mature sandstone is one made of well rounded grains of quartz that are all about the same size 

-slate

-schist

-gneiss

-amphibolite 

-marble

-quartzite

-greenstone 

Foliated- has cleavage

original rock- shale

metamorphic grade- low 

folation- schistosity (flaky)

original rock- shale

metamorphic grade- medium 

foliation- mineral banding (stripes)

original rock- shale felsic igneus

metamorphic grade- high 

foliation- grainy

original rock- basalt

metamorphic grade- medium high 

original rock- limestone

composition- calcite 

original rock- sandstone

composition- quartz 

original rock- basalt

composition- plagioclase, chlorite, and others 

-heat

-pressure

-water 

metamorphic agent

heat 

-deep burial, friction, contact with molten rock

-heated minerals become unstable and change to minerals stable at higher temperatures 

Metamorphic Agent

pressure 

-overburden pressure-- deep burial

-tectonic forces: subduction and plate collision

-rocks bend, stretch, compress, and recrystallize 

Metamorphic Agent

water 

-original pore water in sediments

-water liberated by chemical reactions

-allows movement of ions; facilitate reactions 

minearls will alter to forms more stable at higher temperatures and higher pressure

--garnet

-staurolite

-kyanite

-chlorite

-muscovite

-amibolite

-etc. 

-muscovite

-garnet

-amphibolite 

-parallel orientation of planar features of a rock

-minerals all grow in the same direction

-commonly found in micas

-minerals will grow parallel to the direction of least stress 

-equidimensional minerals grow larger and interlock

-can create strong rock from a weak rock 

-recrystallized limestone

-made of interlocking network of calcite crystals

-has no foliation 

-clay rich regolith frmed from intense in place chemical weathering of bedrock

-commonly retains appearance and structure of original rock

-commonly red or orange (ga red clay) 

-pressure causes rock to crack, water getsin cracks, freezes, and cracks more

-expansion of water to ice

-30,000 psi of pressure

ex. talus slopes and roadway potholes 

-cracks form parallel to surface topography

-creates exfoliation domes and sheeting

-pressure is released which makes large sheets of rocks fall and form large parallel cracks 

Exfoliation

-rock body forms deep in the earth, gets exposed by erosion, and the overburden is removed

-ionic disassociation (dissolution)

-hydrolysis

-oxidation 

-dissolution (add water)

-major factor ony for evaporites (most come from sea water) 

-minerals react with water and carbon

-most important weathering process for silicate minerals

-aided by acidic conditions 

-atmosphere

-microbial respiration products

-CO2 rich groundwater 

Silica weathering products

quartz 

minerals- quartz grains

dissolved material- silica (tiny amount) 

silica weathering products

feldspar 

minerals- clay

dissolved material- silica 

Silica Weathering Products

ferromagnesians 

minerals- clay, iron oxides

dissolved materials- silica 

corners weather away faster

angular boulders become round 

-rock structures (fractures, porosity, foliation)

-minerals (some are more resistant)

*calcite-non resistant in a humid climate

*granite- very resistant to weathering

-climate 

halite and gypsum--- very fast

calcite

most silicates 

-quartz

-clay

-iron oxides 

-different areas weather at different rates

-leaves mixture of high and low features 

O-much organic matter

A- some organic matter; mostly mineral fragments; dark color

E- Little organic matter; clay and soluble material washed out by perculating water

B- material from E accumulates here, clay rich and iron/aluminum rich

C- weathered bedrock 

-Pedalfer

-Pedocal

-Laterite 

-found in the eastern US

-sandy topsoil

-subsoil rich in Iron and Aluminum 

-found in the western US

-enriched in calcite

-light colored 

-found in tropical locations

-no horizons

-enriched in iron and aluminum