Solid Earth summary and notes




Solid Earth summary and notes


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Solid Earth summary and notes


Earth Science 300

Summary notes.

Solid Earth



      definition – naturally occurring, inorganic solid, unique chemical structure

      made of elements, some just one, most more than one

      rocks = aggregate of minerals

      atomic structure – protons, neutrons, electrons

      ion = atom which has gained or lost one or more electrons

      atoms bond to form compounds

            ionic bonding (some atoms lose electrons, others gain them; opposite charges attract)

            covalent bonding (atoms share electrons) - eg. in water to bond H and O atoms

            metallic bonding

      bonded chemical groups often found in minerals, e.g.

            carbonate, sulfate, hydroxyl, silicate

      mineral properties

            crystalline structure





            specific gravity (density)

            hardness (Mohs scale)


4000 named minerals, 8 elements make up bulk of these minerals and represent over 98% of the continental crust:

            O (46.6%), Si (27.7%), Al (8.0 %), Fe (5%), Ca, Na, K, Mg

            Si + O make up silicates = most common mineral group (75% of earth’s crust) –

                  silica tetrahedron, chains

            2 groups of silicates:

                  ferromagnesian (contain Fe and Mg) – dark in color


            feldspars are most plentiful – over 50% of earth’s crust

            quartz = 2nd most abundant

silicates form from molten rock as it cools, and crystallize at different temperatures

¼ of the earth’s crust are nonsilicate minerals:

      carbonates = eg. calcite (major constituent of limestone and marble)


      halite (salt)

gemstones (many have names different from their mineral names)


      sapphire = corundum = aluminum oxide + impurities

            with titanium + iron (blue sapphire)

            with chromium (red ruby)



      The Rock Cycle

      Igneous Rocks

            form as magma cools and crystallizes

            sometimes ejected in volcanic eruptions (extrusive or volcanic), contain vesicles

            sometimes crystallizes at depth in the earth (intrusive or plutonic)

if magma cools slowly – large crystals, quick cooling – small crystals, instant quenching – no crystals (glassy)

Bowen’s series for crystallization temperature

Classification of igneous rocks –

      by amount of silica present

            rich = felsic (eg granite, rhyolite)

            intermediate (eg diorite, andesite)

            poor = mafic (eg. basalt, gabbro)

            low in silica = low viscosity = flows easily

            high in silica = high viscosity

      kinds of feldspars present, other minerals


      Sedimentary Rocks

            weathering moves particles and deposits them as a sediment

            compaction and cementation

            majority of rocks exposed at earth’s surface are sedimentary

            important for determining earth’s history (put down in layers, contain fossils)

            lithification (= transformation of sediments into sedimentary rock)

2 sources of particles (solid – from weathered rock = detritus) (soluble material = chemical sedimentary)

detrital – dominated by clay minerals and quartz

      classified by particles size (eg. conglomerate, sandstone, shale)

      particle size related to distance from source and transport mechanism

chemical sedimentary rocks

      material carried in solution to lakes and seas

      physical precipitation

      biochemical (water ingested by water-dwelling creatures and solid material is

            precipitated out to make hard parts - eg sea shells)

      most abundant = limestone (calcite), 90% is biochemical

      halite (rock salt), gypsum, chert


      Metamorphic Rocks

            can form from igneous, sedimentary or other metamorphic rocks

            changed by heat, pressure, chemically-active fluids

            metamorphic changes take place a few km below earth’s surface

            metamorphism can align grains in rocks

            contact metamorphism – rocks are heated by adjacent mass of hot rock

            limestone -> marble

            sandstone -> quartzite

            basalt -> amphibolite


Plate Tectonics

evidence for movement of plates:

            continental fit

            glacial (including pattern of striations)


            mountain ranges (Appalachians extend into Greenland)

magnetic evidence (trace the apparent direction of the Earth’s N. magnetic pole)


            discovery of Mid-Atlantic Ridge

            evidence of sea-floor spreading

types of crust:

continental, oceanic –  density difference – oceanic is thinner and denser, continental is lighter and thicker.  When 2 plates come together the oceanic plate is the one that subducts

      plate boundaries:

            divergent vs convergent – know structure of these (eg. subduction cross-section)


oceanic: Mid-ocean ridges with rift valley

continental: eg. East African rift valley


      oceanic-oceanic: volcanic island arc, offshore oceanic trench, eg. Aleutian islands

      oceanic-continental: volcanic mountain belt, orogenic mtns, eg. Andes

      continental-continental: (collisional) mountain belt (only minor volcanism) eg. Himalayas


            fault valley, eg. San Andreas fault

            right lateral vs. left lateral

            driving force = convection in the mantle, push-pull force in slab


      fixed point sources of heat (rising magma)

      moving plate causes chain of islands to form



      focus (= location of rupture within the earth)

            shallow, intermediate, deep

epicenter = point on earth’s surface above focus

            determining the position of the epicenter

location of earthquakes (on plate boundaries)

      seismic waves

            body waves (P and S waves)

P waves = primary = compression waves = fastest

S waves = secondary = perpendicular to direction of propagation, do not travel through liquids, slower (do not travel through outer core, produce shadow zone)

            surface waves (produce rolling or swaying motion)

      determining earthquake location from 3 seismographs

      intensity and geology (build your house on rock)

      magnitude (Richter scale)

      intensity (Mercalli scale)


Internal Structure of Earth

inner core – solid (iron with nickel)

outer core – liquid (iron + nickel)

mantle = silicates

      lower mantle = rigid

upper mantle = asthenosphere (plastic) + lithosphere (solid – includes oceanic (basaltic) and continental crust(granitic))


Mountain Building

deformation of rocks and metamorphism of rocks are results of mountain building

response of rock to stress depends on temperature, pressure, strain rate and rock type

stress = pressure = force/area

compressional (usually in mtn building)

tensional (eg. Rift valley)

shear (eg. faults)

strike-slip faults vs dip-slip faults

normal fault, reverse fault, thrust fault

hanging wall and footwall

horst = uplifted block with faults on either side

graben = block that has dropped down

materials which break under stress = brittle

materials which deform permanently = ductile

folds = ductile deformation

folds which arch upwards = anticlines

folds that bend down = synclines

plane along middle of fold = axial plane

      dip = angle layer makes with the horizontal



      molten rock below surface = magma

      molten rock on surface = lava

      types of igneous rock

relationship between amount of silcate in rock, viscosity of rock, type of volcanic explosion, type of volcano, ie.:

  • basalt, low in silica, dark in color, runny, flows easily, can flow through cracks (fissures), comes from mantle and molten oceanic crust, forms non-explosive volcanoes, shield volcanoes (broad domes)
  • rhyolite, high in silica, light-colored, thick and viscous, comes from molten continental crust, explosive, steep-sided volcanoes, stratovolcanoes (steep sides)
  • andesite, intermediate rock (named from Andes mtns) when melted oceanic crust or magma from deep in mantle mixes with molten continental crust, eg. under oceanic-continental convergent plate boundary

      3 places where volcanoes occur:

Rifts (oceanic or continental )

Hot spots

Subduction zones


Geologic Time

  • relative dating – use geological record to order events sequentially
  • principle of superposition – oldest layers under newer layers
  • sediment settles in horizontal layers
  • principle of cross-cutting: fracture must be younger than the rock it cuts; feature that cuts across a rock must be younger than the rock it cuts
  • principle of inclusions – fragments of rock contained within another rock are older than the rock layer containing the inclusions


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