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Geology terms from "Earth's Dynamic Systems" Chapters 1-6

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Simple 3 part composition of the earth
Crust-Mantle-Core
Lithosphere
Crust and upper part of mantle
Asthenosphere
Less rigid upper part of mantle. Material melts or nearly melts here. Rocks lose strength and become plastic here.
Mesosphere
Strong, rigid mantle area. High pressure at this depth offsets the effect of high temperature
Solid Inner Core
Dense part of core
Liquid Outer Core
Circulation of this part of the core generates Earth's magnetic field. Flows because of heat loss from the core and rotation of the Earth.
Atmosphere
-.0001% (2mm over surface)
-all air has water (few % to 100%)
-resting time = 10 days
-it's small, but important, especially storms and distance of water
Hydrosphere
-Definition: total mass of water of surface of our planet
-Covers about 71% of the surface
-98% in oceans
-Water permitted life to evolve and flourish; every inhabitant on Earth is directly or indirectly controlled by it
-Necessary for life
-Regulates climate
-Transfers heat/mass
-Most important erosion agent on land
-Trap for sediment
Biosphere
-Definition: the part of the earth where life exists
-Consists of more than 1.6 million described species, 3 million more not yet described
-Uneven, more biomass/species near the equator (warm and wet)
-Fossil fuels from biosphere
-Model for oil/gas environment
-Model for environment of past life
-Model for sedimentary rocks
-Role of life in evolution of crust, atmosphere, hydrosphere
-Main factors controlling the distribution of life on our planet are temperature, pressure, and chemistry of the local environment
-Formed all the Earth’s coal, oil, and natural gas
-Much of the rock in Earth’s crust originated in some way from biological activity
Crust
-Elevation difference between ocean and continent
-Water runs downhill to basins
-Continental crusts and oceanic crusts
Continental Crust
Include shields, stable platforms, and folded mountains
Shields
-complex of metamorphic rocks and a variety of igneous rocks
-the upper surface is flat and commonly eroded to near sea level
-complexly deformed ancient crystalline rocks exposed at surface
-also called basement rocks, basement complex
-low relief (elevation difference between the low and the high spots), few 100’s of meters elevation, local relief – variability resistant rocks
-complex structure and rock type
Stable Platform
-no major tectonism
-shield + veneer of sedimentary
-flat lying sedimentary rocks (broad domes, basins)
-craton
-when a basement complex is covered with a veneer of sedimentary rocks
Craton
the stable continental crust, including the shield and stable platform area
Basement complex
rocks of shields are high deformed igneous and metamorphic rocks, covered with a layer of horizontal sedimentary rock
Folded Mountains
-rock resistant to erosion, folded, intruded
-along continental margins
-when eroded, form shield, basement
-less dense than ocean
-ancient
-deformed by horizontal stress during slow collision between two lithospheric plates
Oceanic Crust
Includes oceanic ridge, abyssal floor, seamounts, trenches, and continental margins
Oceanic Ridge
-continuous broad fractured rise,
-top of ridge as much as 3000 m higher than adjacent ocean floor
-rift valley
Rift Valley
crack like surface that runs along the axis of the ridge throughout much of its length, long fracture zones
Abyssal Floor
-relatively broad and smooth
-abyssal hills cover much of the sea floor
-abyssal plains
Abyssal Plains
near continental margins, land derived sediment completely covers abyssal hills
Seamounts
-isolated peaks of submarine volcanoes
-some are chains, like Hawaii
Trenches
-lowest areas on Earth’s surface
-invariably adjacent to chains of volcanoes called island arcs
-linear
Continental Margins
-continental shelf
-the zone of transition between a continent and an ocean basin
-continental slope-more dense
-young
-not folded like mountain belts
Continental shelf
submerged part of continent
Continental Slope
marks the edge of the continental rock mass, found around the margins of every continent and around smaller fragments, longest and highest slopes on Earth
Heat Exchange
-Makes the planet dynamic
-Drives from the interior of the earth
-Convection moves mass
Dynamic
a system that is composed of individual items or components that work together to make a unified whole, and in this, material and energy move about and change from one form to another
Conduction
Heat transfer through a mass
Convection
Heat transfer as a result from the movement of a mass
Radiation
Heat tranfer from electromagnetic waves from the sun
Heat Transfer
-drives hydrologic and tectonic systems
-heat transfers from hotter to cooler regions always
Heat Flow
Flow of heat from the interior of the earth
4 systems of weather and climate
evaporation, precipitation, condensation, transpiration
Atmospheric Circulation
-Hydrologic systems redistribute water across the earth
-Moisture rises with warm air, air cools water falls
Hydrosphere Budget
-Ocean 97.5% many sources, sinks, evaporation, residence time 3,000 years
-Ice (glacial in Antarctica and Greenland) 2% residence time of 10,000 years
-Groundwater .5% occurs almost everywhere in subsurface, residence time 1 month-100’s of thousands of years, depending usually on how deep it is
-Lakes residence time: 100-200 years
-Rivers residence time: 20 days
-Plants remove a lot of water from the ground
-Streams, ice, waves, groundwater modifies most of surface of continents
Residence time
average amount of time a tiny bit of water spends in wherever
Why does the hydrosphere move?
-Gravity – how does it get to a high location – why not all flowed long since to oceans and stayed there?
-Storms—circulation—heat flow
-Heat source (sun)
-General circular pattern, water vapor redistribution by atmosphere
-currents—driven by wind, upper 300m of ocean
Water vapor redistribution by atmosphere
-warm, moist air rises at equilibrium, drops rain
-depleted in moisture, cools, drops, warms at 30 degrees
-evaporates water, moves toward poles
-meets cool air at 50 degrees – storms and precipitation
Reservoirs
Ocean, Ice, Groundwater, Lakes, Atmosphere, Rivers, Living Organisms
*These are driven by convective heat transfer
Ocean
-97.5% water
-90% returned by precipitation, 10% runoff
-only sink is evaporated
-resting time = 3000 years
Ice
-80% not in ocean (2% of total)
-nearly all in Antartica and Greenland
-resting time = 10 ka
-melt, sea level change 100m
Groundwater
-20% not in ocean (.5% total)
-nearly everywhere on land
-soil rest time = 1 month, deep aquifers t=ka to ma
Lakes
-.7% not in ocean, .02% of total
->half in fresh lakes, mostly in Great Lakes, Baikal, East Africa
-resting time = 100-200 years for large lakes (long time to flush pollution)
Rivers
-.0001% at any moment
-resting time = maybe 20 days
-small, but important, Transfers water between land and ocean, erosion, transport, etc.
-instantaneous volume is small, but carry large volume over time
Living Organisms
transpiration – remove perhaps as much water from ground as rivers
Effects of Hydrosphere
-enormous energy involved
-modifies and destroys effects of tectonic system
-Finite amount of water
-Can locally change water avail (Las Vegas)
-Irrigation, builds salt, need to flood fields to flush, depletes aquifer, subsidence, etc
-Alter sediment budget, costal erosion, Colorado River
Tectonosphere
-Helps explain why mountain ranges and mid ocean ridges are located where they are
-Temperature is an important factor
3 Ways Plates Interact with Each Other
-Move apart from each other, mainly at mid ocean ridges
-Plates come together
-Plates slide past each other
Theory of Plate Tectonics
-Movement can be measured (not a theory)
-Mechanisms that drive motion uncertain (being tested theory)
-Plate Tectonics is to geology as DNA is to genetics: unifies, clarifies, explains major features of the earth
-Radical change in the view of the earth
Features of Plates
-Continental margin + plate margin not always same
-Some plate have no continental material
-Some boundaries uncertain
Convergent Boundaries
plates come together, produces volcanism, types: oceanic crust to oceanic crust, continental crust to oceanic crust, continental crust to continental crust
Transform Boundaries
-Boundary between two moving lithospheric plates, usually along an offset segment of the oceanic ridge
ex: San Andreas Fault
Divergent Boundaries
plates pulled apart
Divergent Margins
-Spreading, upwelling, form of new crust, hot—low p—high, high heat flow (convection)
-Offset by trans. Faults
-New margin – Red Sea vs Atlantic
-Lower top and deeper water at lithosphere cools away from the ridge
-Motion perpendicular to ridge
-Pangaea: super continent that broke up a long time ago
-Lithosphere beings to pull apart
-Rift valley thins
-Crust becomes thin so it produces oceanic lithosphere
Convergent Margins
-Geology complex and varied
-Cool, hi-p plate descends (subduction) (convection)
-Subduction not necessarily perpendicular to ridge
-Accetionary wedge
-Oceanic-oceanic “island arc”
-Ocean-continent(with and without magmatism)(with and without mountain belts)
-continent-continent (not true sub—underring, thickening, compression)
Intraplate Processes
-Plumes (Hawaii, Yellowstone) (convection)
-Age vs time relation
Tectonic Feature of MOR
divergent margin
Tectonic Feature of trench
convergent margin or sub zone
Tectonic feature of folded mountain belt or volcanic arc
convergent margin
Tectonic feature of volcanism
margins of all types
Definition of Mineral
-Naturally occurring
-Inorganic solid (one exception)
-Internal structure
-chemical composition varies within limits
-exhibits physical properties
-stability limits – but may be broad or narrow
-basic building blocks of rocks
Atom
-comprised of protons and neutrons, surrounded by electrons, distance across atom is about an angstrom (A with circle over it)
-elements unique by number of protons, and variation in electrons and neutrons
-if e≠Z, it’s an ion (charged)
-the type of bond has a strong influence on mineral property
Covalent Bonds
-share electrons
-these are strong
Ionic Bonds
-occurs when one atom in bond gives up an electron/s and the other one takes it, so they become ions with opposite charges, and opposites attract
-these are weak
-tend to come apart in water, soluble in water
Most Common Elements
H, O, Si, Al, Fe, Mg, Ca, K, Na, C
Why do Mg and Fe substitute?
Mg^2+ is .72 ang; Fe^2+ is .78 ang.
Important properites of structure and composition in minerals
crystal form, cleavage, hardness, density, color, streak, etc.
Rock Forming Minerals
-feld, mica, amph, px, ol, qtz, cc, dol, clay, halite, gypsum
-make up almost all of the upper mantle and crust
Solid Solution
-can vary within minutes
-Olivine can have formula between MG2SiO4 and Fe2SiO4
-you can’t think of a crystal as a molecule
-for every 19 magnesium atoms, there’s an iron
-narrowly defined limits
-atoms can substitute for each other based on size and charge
-a lot of solid solution substitutes occur for elements on the same column on the periodic table
Physical Structure of Diamond and Graphite
-Diamond, made out of carbon (covalent bonds really strong)
-Graphite, made out of carbon
-Diamond and Graphite differ in the way the bonds work
Hot Spots
-melting beneath lithosphere, islands get older and older, Hawaii Island example, Yellowstone
Plates
-Plate continental boundaries may be, but need not be, in the same location
-Plate motion differs at boundaries: divergent perpendicular, transform parallel, convergent between
Internal structure of Pyroxene
-There is a unique manner in which the atoms are bonded together, specific geometric pattern
-Example of a mineral that shows unique internal structure
Which mineral always has a fixed composition?
Pyrite (FeS2)
Cleavage
how a mineral breaks
Meta Stable
rock just waiting to be pushed off a cliff, needs the pushing energy to change
What is the most abundant mineral in the earth's crust?
Feldspar
Magma
-Molten rock [melt+/-gas+/-crystals] cools to igneous rocks
-Hot, partially molten rock material. Most are a combination of liquid, solid and gas.
-Forms igneous rocks when it cools
-Intrusive rock – Magma that solidifies below the surface
-Extrusive rock – Magma that has reached the surface (becoming lava) without completely cooling and flows out over the landscape.
Texture of Magma
-glassy
-aphanitic
-porphyritic-aphanitic
-porphyritic
-phaneritic
-porphyritic-phaneritic
-pyroclastic
Glassy texture
Taken from a temperature when crystals would normally form and then cooled rapidly/quenched.)
Aphanitic texture
-microscopic crystals [extrusive, cooled quickly, but not too fast, not glassy]
-Relatively rapid cooled
-Made of numerous small spherical or ellipsoidal cavities called vesicles. They are created by gas bubbles trapped in the solidifying rock.
Examples of rocks with Aphanitic texture
-Rhyolite – Has the same silicic composition as granite. Not common along ocean ridges or oceanic islands but is more common on the continents
-Andesite – Most abundant lava type after basalt. Occurs mostly along convergent plate margins in island arcs and along continental margins. It is rare in oceanic islands.
-Basalt – Most common aphanitic rock. It is abundant on the seafloor
-Komatiite – Rare volcanic rock. Found mostly in very ancient rock sequences exposed in the continental shields.
Porphyritic-aphanitic texture
aphanitic rock with phenocrysts [like aph, but erupted magma with x’ls]
Porphyritic texture
-2 stages of cooling: Initial stage of slow cooling in which large grains develop Followed by a period of more rapid cooling during which the smaller grains formed
-Phenocrysts – larger, well-formed crystals
-Smaller crystals – matrix and the groundmass
Phaneritic texture
-visible crystals [intrusive, cooled slowly]
-Uniform (very slow) rate of cooling and large crystals
-Composed of grains large enough to be recognized without a microscope
Examples of rocks with phaneritic texture
-Granite – coarse grained igneous rock composed predominantly of feldspar and quartz
-Diorite – Similar to granite in texture; Plagioclase feldspar is the dominant mineral
-Gabbro – Not usually found at the at the earth’s surface. Makes up the lower part of the oceanic crust and is present at some intrusions. Composed of pyroxene, calcium-rich plagioclase, and olivine.
-Peridotite – Composed mainly of olivine and pyroxene. Makes up a large portion of the mantle and is not common on the surface.
Porphyritic-phaneritic texture
rock with phenocrysts [intrusive, cooled slowly in two stages]
Pyroclastic texture
-ash, crystals, pumice, rock fragments [explosive]
-Produced when explosive eruptions blow crystals and bits of still molten magma into the air as a mixture of hot fragments called ash
Examples of rocks with pyroclastic texture
-Ash – dust sized pieces
-Pumice – vesicular froth glass common among the lager fragments
-Tephra – shards of volcanic glass, pumice, broken phenocrysts, and foreign rock fragments
-Tuff – the rock resulting from the accumulation of pyroclastic fragments
Extrusive Rock Bodies
-basalt lava flows
-silicic
-explosive volcanism
Basalt Lava Flows
-Aa – moves slowly. The hardened crust is broken into a jumbled mass of angular blocks and clinkers.
-Pahoehoe – more fluid than aa flows. “Fossil gas bubbles” make the rock light and porous.
-Vesicles – Small holes formed in a volcanic rock by a gas bubble that became trapped as the lava solidified
-Fissure eruptions – Instead of issuing from a central vent, basaltic lava is commonly extruded from a series of fractures in the crust (fissures).
-Lava lakes – Collapsed caldera (summit craters) that may fill with lava
-Lava tubes – Fluid interior breaks through the crust and flows out.
-Bombs – large projectiles blown from a volcano
-Cinder cone – larger particles that accumulate close to the vent
-Shield volcano – Fluid basaltic lava flows freely for some distance, spreading into a thin sheet or tongue before congealing. Shield volcanoes have wide bases.
-Columnar joints – flows that cool, contract and may develop a system of polygonal cracks. Similar to mud cracks.
-Pillow lava – Extrusion of basaltic lava into water produces a flow composed of a multitude of ellipsoidal masses
Silicic
-Rhyolite domes
-Stratovolcano or composite volcano – a high, step-sided cone centered around the vent formed by alternating layers of tephra and thick, viscous lava flows or domes
(Lavas, Tephra, Lahar, Calderas)
Explosive Volcanism
-Like shaking a can of pop – When opened CO2 comes out violently – In a volcano H2O, CO2 and magma come out of solution violently
-Expands and rises in a cloud of ash, pumice, crystals and country rock
-Airfall or flow at hundreds of km/hr at hundreds of degrees Celsius
-Airfall (ash?) – Smaller particles of ash that form ash cloud?
-Welded Tuff – a rock formed from particles of volcanic ash that were hot enough to become fused together
-Lateral blast – blast occurring laterally
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