GEOL 201 Exam 1 Review Questions

Introduction- Nature of Science and Global Earth Systems

what underlying assumptions about the universe does science depend on?

universe is comprehensible and follows predictable regularities

describe the scientific process

1. observe something

2. develop a hypothesis

   1. propose explanations base on observed patterns

3. test hypothesis

   1. generate expectations/predictions from new observations/testing

   2. modification or rejection based on new observations)

4. Create Theory

   1. Confidence in theory increases as more independent observations support its predictions

   2. Theory is well-supported & built from many tested hypotheses

what are the purposes of science?

1. explain the world around us

2. not about accumulation of facts

3. theories are the goal and focus

   1. bring unifying explanations

differentiate between Methodological Naturalism and Epistemological Naturalism

1. methodological naturalism

   1. scientific inquiry

   2. how we should investigate nature

2. epistemological naturalism

   1. knowledge and justification

   2. what is knowledge/justification and how should we study it)

what are the 3 principal sources of energy that drive earth systems? what does each particularly do?

1. gravity

   1. important for all earth systems, keeps earth together

2. energy from the sun

   1. drives climate system, source of energy for nearly all of earth's ecosystems

3. energy from earth's interior

   1. drives plate tectonic systems, movement of plates, our volcanoes

how does differential heating of the earth's surface drive atmospheric circulation?

differential heating of the earth's surface drives atmospheric circulation because heat rises, and then lowers as it cools, so it causes a current throughout the planet

what are Hadley Cells?

-warm, moist air rises at the equator

-surface winds blow toward the equator as trade winds due to the Coriolis effect

-tropics and subtropical deserts

-hot and dry

-hot and wet

what are Ferrel Cells?

-between Hadley Cells/Equator and Polar Cells/Pole

-surface air flows poleward and eastward, while upper-level air moves equatorward and westward

-cool and wet

what are Polar Cells?

-at the poles

-cold, dense air sinks at the poles, flows towards equator along surface

-cold and dry

describe the hydrologic cycle:

water cycle

1. evaporation

2. condensation

3. precipitation

describe the rock cycle:

1. igneous rocks

   1. comprise 95% of earth's crust

   2. rocks formed when hot molten magma cools

2. sedimentary rocks

   1. formed from sediment and dissolved chemicals produced by weathering and erosion

3. metamorphic rocks

   1. pressure and heat alter composition and texture of rocks

of the 3 principal types of rock, which composes 95% of the earth’s crust?

igneous rocks

what causes the earth to be very hot at the center? what does this energy do and how does it get “lost” over time?

energy from earth’s interior

• trapped heat from gravitational collapse at origin and from radioactivity

  • gradual release to space by conduction and convection

what are the layers of the earth in order from the core out?

1. core (inner and outer)

   1. metallic iron and nickel (gold)

2. mantle (lower and upper)

   1. upper mantle contains asthenosphere and lithosphere

3. crust (continental and oceanic)

   1. aluminum rich silicates

which layers are solid, which molten and why?

• solid inner core

• molten outer core

• solid lower mantle

  • partially melted zone in upper mantle

what is the asthenosphere?

Partially melted zone in upper mantle

• partially melted with slow convection

  • upper layer of mantle, below lithosphere, low resistance to plastic flow

what is the lithosphere?

rigid uppermost mantle and crust

• what we know as the “plates” that move relative to each other over underlying asthenosphere

why are some layers of the earth molten and some solid?

• partial melting in mantle where temperature exceed melting point

  • pressure increases temperature that must be reached for it to melt (playing between the two to find the zone where there is more pressure than temperature (solid) or more temperature than pressure (liquid))

how do temperature and pressure change with depth?

they both increase with depth

at what average depth does flux melting begin to occur on the top edge of crustal plates?

150m

what is flux melting?

a geological process where the addition of water and other volatile gases lowers the melting point of hot solid rock, turning it into magma

why can rock at great depths remain solid at very high temperatures?

pressure increases melting point

what generates the earth’s magnetic field?

combined effect of rotating solid metallic inner core and convection of outer core

what is more dense? oceanic or continental crust? why?

oceanic because of the pressure on it from all of the ocean water on top of it, and the sediment being compacted onto it as well

what energy drives plate tectonics?

convection currents of asthenosphere

• divergent boundaries correspond to zones of rising hot mantle, and convergent boundaries to zones of sinking cooler and denser mantle

describe what tectonic situations created pushing forces, pulling forces?

1. gravity “push” from mid-ocean ridges

   1. ridge push

2. gravity “pull” from cold dense sinking lithosphere at subduction zones

   1. slab pull

what evidence suggests that earth’s crustal plates have been in different positions in the past?

1. match of continental margines

2. similarity of geology and fossils on now separated continents and not within the ocean

3. patterns of distribution of ancient climates (glacial deposits, sand dunes, coals, etc.)

how can we know scientifically how fast the plates are moving? when they were at other positions?

• from the age of seafloor crust and sediments

• current relative motions can now be measured by GPS satellites

  • calculated in cm/yr

who first proposed the idea of continental drift and when?

Alfred Wegener, 1915

why did it take more than 50 years to be accepted?

new evidence to support idea of lateral movement of continents and new evidence from seafloorh

ow can we know earth’s magnetic poles have moved and even reversed with time?

The direction and inclination of the earth’s magnetic field at a particular place and time can be recorded in iron bearing rocks

• thermo-remnant

• detrital remnant magnetism

• chemical remnant magnetism

what is thermo-remnant magnetism?

iron oxide minerals in igneous rocks such as basalt may preserve the orientation of the magnetic field when they cool below the curie point

what is detrital remnant magnetism?

magnetic grains in sediments may align with the magnetic field during deposition

what is chemical remnant magnetism?

magnetic grains grow within rock and record the magnetic field direction at the time of their formation

describe tectonic situations that coincide with seafloor spreading in continental and sea floor crust:

rifting at center of ridge with eruption of magma from underlying mantle → creates new ocean crust

describe tectonic situations that coincide with subduction zones in continental and sea floor crust:

• oceanic lithosphere is destroyed and recycled back into the mantle

• cool lithospheric slabs sink into the underlying mantle

• deep ocean trenches

• volcanic island chains

  • melting of ocean crust → explosive volcanoes

describe tectonic situations that coincide with hot spots in continental and sea floor crust:

region with thinner lithosphere crust/hotter mantle/magma underneath, where volcanic activity occurs

what is the Wadati-Benioff zone?

inclined earthquake zones mark where there are subduction zones/close to them

describe the divergent continental margins and how the collision zones between different continental margins vary

• shallow earthquakes, tensional faulting

• upwelling of magma from mantle, basaltic lava flows

• 2 types:

  • mid ocean ridges: formation of new ocean

  • continental rift valleys: may lead to formation of new ocean basins

describe the transform continental margins and how the collision zones between different continental margins vary

• curved fracture zones

• shallow earthquakes → lateral fault movement

• 2 types:

  • lateral offset of mid-ocean ridges

  • continental transform fault

describe the convergent continental margins and how the collision zones between different continental margins vary

3 types:

1. ocean-ocean

   1. one plate subducts under the other, lithosphere melts, and becomes magma → creating volcanoes

   2. explosive volcanoes

2. ocean-continent

   1. ocean goes underneath continental

      1. produces volcanoes/mountains island

3. continent-continent

   1. deformation and uplift of mountains

   2. regional metamorphism

   3. large earthquakes

subduction zones associated with ocean-ocean and ocean-continent

describe the passive continental margins and how the collision zones between different continental margins vary

transition zone between continental and oceanic crust, but it is not on a plate boundary (difference between crusts, but all one plate)

what is the ring of fire?

belt of active volcanoes and frequent earthquakes surrounding the pacific ocean due to being at tectonic plate boundaries

what is an island arc of volcanoes is Hawaii an island arc?

Island arc: chains of volcanic islands formed along subduction zones where one oceanic plate sinks beneath another, producing explosive volcanism and intense seismic activity

Hawaii is not an island arc

• formed by hotspots, not subduction zones

what are atoms, protons, and electrons?

Atoms: smallest unit of an element that retains all its properties (composed of protons, neutrons, and electrons)

what is an element, what defines them?

element is defined by the number of protons (atomic number)

what makes an element “stable”?

balanced number of electrons and protons (8 electrons in outermost shell)

what are cations? anions? iconic and covalent bonds? why are covalent bonds so stable?

cations: positively charged ions

anions: negatively charged ions

ionic bonds

• transfer of electrons from one element to another

covalent bonds

• sharing of electrons

• strong because they share, creating stable configuration for each atom involved

• ex: diamonds

metallics bonds? why are metals malleable, ductile, and electrically conductive because of their bonds?

• outer electrons of metallic solid are free to move around (electrons not bound to any atoms)

• freely moving electrons result in malleability, ductility, and electrical conductivity

what are the characteristics of minerals? minerals are the building blocks of rocks

characteristics

• crystal structure

• cleavage

  • break in preferred directions

  • due to planes of weakness from bonds or spacing of atoms

• set chemical composition

• naturally occurring

• homogeneous

• solid (at room temperature)

what are crystals?

• molecules/atoms arranged in highly ordered, symmetric, 3D pattern

• internal crystalline structure

what are the common cleavage planes of minerals that we studied and why do they exist in each? ex: graphite cleaves in single sheets of carbon atoms, arranged in groups of 6 carbon atoms because of weak bonds between C of adjacent sheets

cleavage: (controlled by internal arrangement of atoms) planes of weakness due to types of chemical bonds or spacing of atoms

types:

• 1 plane

• 2 at 90

• 2 not at 90

• 3 not at 90

• 4

describe the chief properties of minerals (hardness, density, color, streak, luster) and how can they help identify mineral specimens?

1. hardness

   1. determined by strength of atomic bonds

   2. Moh’s relative hardness scale (1-10)

2. density

   1. increase with mass of elements and closeness of their spacing in the crystal structure

3. color

   1. highly variable (due to trace elements)

      1. high iron content → dark

      2. aluminum → light

4. streak

   1. color of mineral when powdered

5. luster

   1. quality and intensity of reflected light from mineral surface

why are silicate minerals so abundant, especially in exposed surface rocks?

• oxygen and silicon comprise 75% of earth’s crust

• fundamental unit of silicate minerals is silicon-oxygen tetrahedron

• more than 90% of rock forming minerals are silicates

describe the crystal formation of Olivine Group minerals. how are the isolated silica tetrahedra held together to form Olivine?

• silica tetrahedra held together by ionic bonds with iron (Fe)++ and magnesium (Mg)++

• held together by cations between silica tetrahedra

• no planes of weakness and thus no cleavage

• hardness 6.5-7

why is quartz so hard and yet has conchoidal fracture patterns? describe arrangement of silica tetrahedra in quartz crystals

• quartz is so hard because of its covalent Si-O bonds which are nearly equal strength in all directions

  • all silica tetrahedra joined with no cations - SiO2

• it lacks weak planes where it can split easily, therefore stress cannot travel along preferred path, so bonds break randomly causing conchoidal fracture

describe the crystal formation of Pyroxene Group minerals. how are the isolated silica tetrahedra held together to form Pyroxene?

• held together in single chains

  • chains joined by ions of Fe, Mg, Ca, Na, and Al

  • cleavage 2 planes at 90

  • hardness 5-6

describe the crystal formation of Amphibole Group minerals. how are the isolated silica tetrahedra held together to form Amphibole?

• held together in double chains

  • chains joined by ions of Fe, Mg, Ca, Na, and Al

  • cleavage

    • 2 planes at 56 and 124

  • hardness 5-6

describe the crystal formation of Mica Group minerals. how are the isolated silica tetrahedra held together to form Mica. how is Biotite different from Muscovite?

• sheets of tetrahedra bound by aluminum and hydroxide (OH-) ions, double sheets loosely bound by Potassium ions

• perfect single cleavage

• biotite

  • dark, iron and magnesium rich mica

• muscovite

  • light, iron poor mica

describe the crystal formation of Feldspar Group minerals. how are the isolated silica tetrahedra held together to form Feldspar?

• oxygen atoms of silica tetrahedra are shared forming a 3D framework

• most abundant rock-forming mineral

how are orthoclase feldspars different from plagioclase feldspars?

• orthoclase

  • K feldspar

  • has 2 at 90

how do plagioclase feldspars vary continuously in their Ca/Na concentration (think Bowen’s series)

• plagioclase

  • Na to Ca feldspar

  • 2 at 86

what are halide minerals? how do they form?

• ionic solids formed with elements with only one electron short of a stable number

• evaporite minerals

what are carbonate minerals? how do they form?

• ionic solids with complex carbonate ions

• cations join with carbonate ion

what are sulfate minerals? how do they form?

• ionic solids with complex sulfate ion (SO4)2-

• evaporite minerals (Anhydrite, Gypsum)

what are sulfide minerals? how do they form?

• bonding of element with sulfide ion (S2-)

• Pyrite FeS2

• includes ores of important metals (Copper, Zinc, Lead)

• most have a metallic appearance

what are Oxide minerals? how do they form?

• oxygen bonded to other elements, usually metallic ions

• most metal oxides have ionic bonds

what minerals tend to occur as native elements?

• some elements occur as pure minerals in nature

• Copper, Gold, Silver

• Sulfur

how do igneous rocks form? differentiate between extrusive and intrusive igneous rocks

• form from solidification of magma

  • magma from melting of mantle or lower crust

  • magma rises toward surface

• intrusive igneous rocks

  • intrude into surrounding rock below surface

  • intrusive rocks crystallize beneath the earth’s surface from magma

• extrusive

  • extruded at surface

  • extrusive rocks form from lava that erupts onto the surface

describe 3 different causes of melting magma? what is flux?

• decompression: rising mantle decreases in pressure lowering the melting point of rock

• addition of volatiles (flux): adding volatiles such as water and CO2 to hot mantle rock lowers its melting temperature; this occurs at subduction zones

• heat transfer: rising very hot magma from mantle transfers heat to surrounding crustal rock

what is partial melting?

• as the temperature of rocks are raised, the minerals within them melt at different temperatures

• minerals with higher silica content melt first because of lower melting temperatures, minerals with high magnesium and iron have higher melting temperatures

• mixture of melt and crystals produced

how are igneous rocks classified based on mineral composition and texture/crystal size?

• Bowen’s reaction series describes the sequence in which minerals crystallize from a cooling magma

  • increase in silica content with cooling

  • increase in sodium (NA) and potassium (K)

  • decrease in iron (Fe) and magnesium (mg)

• Felsic: high silica and potassium rocks

• Mafic: high iron and magnesium rocks

what aphanitic?

• fine grained texture

• microscopic mineral grains

• rapid rate of cooling

• small or sheet-like intrusive magma bodies at shallow depths

• extrusive igneous rocks, lava flows

what is phaneritic?

• coarse grained texture

• slow rate of cooling

• intrusive igneous rocks

• large bodies of magma cooling below surface

what is porphyritic?

• large crystals in a fine-grained matrix

• result of cooling at different rates

what is pegmatitic?

• extremely course grained igneous rock

what is pyroclastic?

• volcanic rock fragments fused together

• volcanic tuffs, ash with pumice fragments

how does silica composition change in magma as it rises up to the surface?

silica composition increases in magma as it rises

describe Bowen’s series

felsic

high silica and potassium rocks

mafic

high iron and magnesium rocks

how can a single magma produce many different kinds of igneous rock?

• crystallization of magma

• different minerals crystallize from cooling magma at different temperatures

• as mineral grains form, the composition of the remaining liquid changes

• composition of crystallizing minerals and liquid continually changes as magma cools

what are country rock?

pre-existing older rock

what are xenoliths?

chunks of wall rock incorporated into magma

what is stoping?

step-like areas from rock removal

what are laccoliths, dikes, sills, plutons, and batholiths?

intrusive igneous bodies

what are laccoliths?

intrude between rock layers but force upper layers upward

what are dikes?

cut across pre-existing layering

what are sills?

intrude between rock layers and are parallel to layers

what are plutons?

masses of tens of meters to tens of kilometers across

what are batholiths?

composite plutons put to hundreds of kilometers long

what is a volcano?

• primarily a vent, opening through which magma and gas escape

• form of col