COA401_Geology

decreases

as pressure increases, melting point

increases

both pressure and temperautre ____ toward the center of the Earth

Lithosphere

hard, birttle part of the upper mantle

→ physical state of rocks change with increasing depth

→ higher temperature override the effect of pressure, causing a tiny portion of the rocks to melt

Asthenosphere

partial melting zone in the lithosphere where rocks flow plastically

→ lower part gradualyl becomes rigid as pressure increases

→ rocks are no logner plastic at 350 km below the Earth Surface

Mesosphere

More rigid zone of the mantle that reaches the top of the core

Hydrosphere

exterior envelope that composes of all free water on earth

97% composed of ocean water

Biosphere

exterior envelope comprising of all living and non living organic matters

→ consists largely of carbon, hydrogen, and oxygen compound

→ org matter recycled into the lithosphere

Escarpment

long, steep slopes seperating areas of different heights

Transform faults

type of tectonic motion where fractured rocks slide past one another, casuing segementations of a geologically active area

creates a zig zag pattern

Fracture zones

inactive arms of transform faults that extend into deep-ocean basins

consit of lienar vallyes and elongated, faulted hills that are orientated at 90 degrees relative to its axis

characterized by escarpment

Contential Slope

Seward shelf breaks, inclined at 4 degrees

base lies at water depths of 2-3 km

consists of mud and sand eroded from the conteint that lies underneath the slope

→ hosts submarine canyons

Submarine Canyons

Deeply inclined land forms that cut into sedimentary depoists

serve as chutes of sedimentary depsoits from contnetial margins to deep ocean basins

Continental shelf

nearly flat plains at the top of the sedimentary wedge beneath the drowned edges of contieints

sliopes seaward at a .5 angle

ends at a shelf break, where the contneital shelf edns on the ocewna side the sea bottom steepns appreciably

shelf break

where the contiental shelf ends on the ocean side, the sea bottom steeps appreciably

occurs at water depths of 130 m

Continental Rise

part of the contiental margins, located at the basin of the continental slopes

ocean bottom flattened to a 1 degree gradient

• Can extend more than 500km from the base of the continental slope to water depths approaching 4 km 

• No great topographic relief, except in areas where submarine canyons extend their channels onto the rise 

• Underlain by deposits of sediment that are very thick

  • Derived from the erosion of rock and sediment from nearby landmasses

Continental margins

part of the continent that is submerged underwater

sand and mud eroded from continents transported to the shores and accumulated> become shaped into a thick sedimentary wedge along the continental edge

immense deposits of sediments at contential edges comrpise the contnetial margins

composed of: Shelf, shelf break, slope

Abyssal plains

flattest areas of deep ocean basins

regional slope <.5 degrees

drops vertically less than a meter across 1 km of seafloor

composed of land dervied sediments

→ buried irregular volcanic topography of the solid crust of the ocean

→ debris moved from submarine canyons and spilled out to cover the crust of the deep sea

abyssal hills

domes of deep ocean basins, elongated hills of 1,000m

composed of:

• volcanic rock

• covered in a thin layer of fine grained sediment that has setllted down through the water above

Seamount

part of the deep ocean basin

made of extinict or active volcanos

conical toop and steep sides

Guyots

flattoped sea mounts that were once active volcanos

tops were leveled and flattened by wave erosion

Deep sea trenches

steep, long and narrow depressions basins

can be 3-5km deeper than surrodning ocean floor

deepest regions on earth

close to land, nestled aganist continental margins or chains volcanic islands

associated with active volcanoes and earth quakes

partially filled wit sediment that has been eroded from the nearby landmasses above them

Granite

Contential crust is composed of

Basalt

oceanic crust is primarily composed of

moho

the boundary between the crust and upper mantle

warm, shallow seas

During the age of Pangaea, large portions of the central and western parts of North America were covered by

Mid-ocean ridges

a continuous submarine mountain range that winds its way through all oceans

covers 1/3 of the ocean floor

summit of each ocean ridge is convex or occupied by a rift valley

→ formed by faulting

→ geologically active: characterized by frequent shallow earthquakes

→ show seismicity and volcanism

Submarine canyons

rivers and currents that cut into sedimentary desposits, forming steep V shaped profiles

topographic relief of 2 km

one of the most deeply inclined landforms on Earth

serves as chutes to transfer sediments from contiental margins to deep ocean basins

part of the contiential slope

isostasy

the balance of an object floating upon a floating meidum

→ deep ocean basins and thin and dense, thus do not rise as high above the mantle

thickness, density

Height of the landmass aboe and below the surface of a medium is controlled by____________ and ___________

Alimetry

orbiting satellites use radars to radpily measure the height of the sea surface

→ variations in the height of the ocean reflect the bathymetry below

→ can detect water bound of water over a submarine mountain or volcano

→ can be used to map the ocean’s large scale bathymetric features

Echo-sounding

a sound transmitter mounted on the bottom of the vessel sounds out a sound pulse into the water

→ wave reflects off the ocean floor, where it is recorded by a hydrophone

Side scan sonar

sound directed is sideways to produce a map of the sea bottom traversed by the ship rather than a mere profile of the bottom

valuable for locating sunken ships

seismic reflection

sound pulses reflect on the ocean floor

can ID features within the bottom, revealing the shape and thickness of sediment and rocks beneath the sea floor

uses strong sound pulses and lower frequencies than an echo does

seismic refraction

sound waves bend as they travel through sediment, rock, and waves

reveals: densities, depths, rock thickness

relies on high energies and low frequncies

→ can give the geologic strucutre of crust and mantle

→ most powerful sound pulses

Alfred Wegner

proposes a theory of continental drift based on the fit of contienntal outlines, fossil evidence, geological evidence

100-150 mya

Pangae formed

Mid atlantic ridge

Oceanic ridge algined in the middle of the Atlantic basin

cut by long, linear tranform fauls and fracture zones that divie the ridge axis into many segments, each offset from one another

normal faults

topographic scarps where crustral rocks have broken and dropped past another, creating a valley

occurs along the edges of rift valleys as zones wehre crustal rocks are displaced vertically

→ forms fresh cr

older, distance

baslatic crust becomes increasingly __________ and _____with distance from the ridge line, because of a longer history of spreading and sediment accumulation

Paleomagnetization

occurs as other minearl crystalize, they lock in and trap the alignment of the magnetic grains

grains record the strength and direction of the geomagentic field at the time they crystallized into solid

→ will reflect the polairty of the earth at the time of freeze

Reverse polarity

the periodic switching of Earth’s polarity

has reversed 183 times in the last 83 million years, and at least several hundred times in the past 160 milliom years

magetnic anomaly stripes

reading of the magnetomere that measures either high or lower readings based on the polarity of the earth at the time of magentiization

→ as basalt crust is split at the crest, paris of these are about EQUAL WIDTH, mirror images of eachd other on each side of the flank

1-10cm/yr

rate of sea floor spreading

Tectonism

the deformation of Earth

s crust

Subduction Zones

zone where two plates converge, and one sinks under the other

associated with deep sea trenches and volcanic arcs, deep sea trenches and volcanoes, and mountain belts

→ slab going down generates strong earthqaules as its upper surface slips against the rock above it

→slab melts partially at depths of 100-200kkm

->hot lava rises to the surface and spewed out as volcanic arcs

→ one part of the sea floor plunges below another into the asthenosphere

→ balanced by sea floor spreading (plate growth)

ocean-ocean collisons

type of subduction events where two oceanic plates converge

→ deep sea trenches and volanic arcs

→ aleutian islands

ocean-continent collisons

type of subduction event where a contiental crust and ocean crust converge

→ topography: deep sea trench, volcanoes

→ Andes Mountains

Continent-Continent

type of subduction zone where Continent and continent collison

→ topography: mountain belt

→ no intensity

→ Himalyan Mountains

Thermal Convection

ductile rocks of the asthenosphere begin to rise upward

slow moving currents exert drag on the bottom of the lithosphere plates, setting them in motion

→ drags along the the overlying lithosphere plates away from the crests of ocean ridges

leads dense edges of the lithosphere at subduction zones to pull plate downward, as it sinks to th ehotter astehnosphere

Mantle plume

plume of hot mantle material rises through the lithospehre, spilling out as lava on top of the plate

forming a large volcanic mass

causes the growth of volcanic islands: volcanic plates sticking up past the water surface

Growth of volcanic islands

large volcanic mass at a hot spot are added to a pile, creating a volcanic cone on the ocean floor as the pacific plate drifts over the hot spots> plates stick up past the water surface, can form islands

-> North to North west fomration

→ islands become older and more eorded and lower in elevation as the lithospheric plate drifts north

Embyronic Basin

part of the wilson cycle

spllintering og granite contiental crust, forming long linear rift valleys

fractured by normal faults

motion: uplift

ex: East African rift valley

Juvenile Basin

Occurs when contients are separated into two indepdent masses

baslatic crust forms between them along a young spreading ocean ridge

narrow sea way forms

→ Red Sea

Mature

contiuned sea floor spreading

broad plate ruptures where lithsophere is old and supporting heavy sediment load when large piles of sediment accumlates

→ ocean basin with continental margins

→ Atlantic and Artic Oceans

Declining

Subduction begins where one side of the framented plate overrides the other

elimates much of the sea floor and oceanic ridge

ex: East Pacific Rise

Terminal Stage

when contients on either side of a subduction zone collide, and the last of the sea floor is eliminted

characterized by crust and sedimentary despot uplift

creates a young mountain belt folded and faulted marine sedimentary rocks

→ narrow irregular seas with young mountains

→ ex: Mediterranean Sea

Suturing

plates become sutured tighly togehter throughs edimentary deposition

oceanic crusts are buckled and thrust upward into a mountain range

→ Ex: Himalayan Range

Red Sea

type of juvenille ocean basins that is a result of divergence ebtween african palte and arbian plate

along the center: narrow axial with a expanse of 1000m w/ new baslatic ocean crust forming at the cetner of the sea

→ began to develop 20-30 mya as grantic crust of the plates were stretched until it broke apart a system of normal faults

→ large faults splintered the thick granitic crust into large blocks

→ brine water typically fills the axial trough as a result of flow of groundwater through fractures in underlying rocks

San Andreas fault

example of a transform fault where the sea floor spreading ridge of the Gulf of Califronia with the spreading ridge off of Oregon and washington. Plate motions result in seismic activity

Cascadia Subduction Zone

• 1,000km long dipping fault from northern Vancouver Island to Cape Mendocino Cali 

• Separates the Juane de Fuca and NA Plates

  • New Juan de Fuca plate is created offshore>

  • Shoved beneath the NA plate (continent) 

Benioff Zone

Area of increasingly deeper seismic activity along subduction zomes (45 degrees)

intermeridate and deep earthwuakes ordiante within an incline zone that is tilted away from the deep-sea trench toward volcanic arc

extends to 700km

gravel>sand>mud>colloid

graditation of paricle size (largest to smallest)

Terrigenous sediment

• Fine and coarse grains that are produced by the weathering and erosion of rocks on land 

• Sand or mud

Biogenous sediment

• Fine and coarse grains derived from hard parts of organisms 

• Lime: composed of calcium carbonate 

• Siliceous: composed of silica 

• Formed by shells of skeletal debris 

• Micro and macro algae and organisms 

Hydrogenous sediment

• Particles precipitated by chemical or biochemical rxns in sw near the seafloor 

Volcangeous Sediment

particles ejected from volcanoes

ex: Ash

Cosmogenous sediment

tiny grains that orignate from outer space, mixed into terrigenous and biogenic sediment

particle size distribution

energy conditions at site of deposition

determing factors of sedimentation

high energy conditions

in these conditions, fine grains are contiunally resuspended after momentary settlement.

Constant agitation seperates small grains and transport them into less turbulent water

coarse sand deposited under these condtions

low energy conditions

in these conditions, fine grain sediment settles. Coarse grain are lacking bc weak currents cannot transport them to these sites

mud accumlats here

heterogenous

rapid erosion results in high rate of sedimentation, has this type of depositional form

energy

average particle size is _____ to the energy level present at the time of deposition

homogenous

low rates of sedimentation result in a this type of deposition

Hjulstrom Diagram

shows the average current velocities necessary for erosion, transportation, and deposition of sediment

→as you go down the graph and decreasing particle size, the average velocity needed for erosion decreases then increases again when it hits clay and slt

systematic decrease

in shelf sedimentation, sediments sort them selves into this order (under normal conditons)

150m

2 mil years ago sea levels dropped _____

relicit sediments

sediments locted on the outershelf that were depsoited during low sea levels, thus are LARGER than expected/ would have been depsoitied in normal conditons

2/3

amount of sedimentation that is made up of relicit sediments

tides, waves, currents, and depth

shelf sedimentation is strongly controlled by

river supplied terrigenous deposits

temp/mid lats sedimentation types

Biogenic sediment, primarily calcium carbonate derived from coral

equator/subtropics sediment

glacial till or ice rafted debris

polar shelves sedimentation

repeated glaciation events

The ‘dominant’ Earth-shaping event of the past million years has been

sediment laden bottom currents

submarine cnayons were deepened during interglacial periods by

passive-type continetal margins

distinict conteintal edge w/ a long history of sedimentation

wedge of sediment deposited between the basalt and granite plates forms> contiental margin is widen and thickened as terrigenous sediment erodes to the shelf

> crust and underlying matnel cool and contract

>weighed down by sediment load, edge of contiennt sinks continually, allowing river sediments to flow in

>NOT tectonically active

deep sedimentation

Accretionary prism

a compressional zone situtated between the deep sea trench and the volcanic arc that widens with the time as sediments are deformed and plastered to its seqared

→ mud is scraped off it as it is subducted

→ material from underwater landlsides are crushed aganist this

Active-Pacific type margin

Continental margin where compression from subduction squeezes the bed of sediment between colliding plates, folding and faulting the sediment layers

sedimentary layers and basalt scraped off the top of the plate is forced downward

→ continental shelf tends to be narrow and to have an irregular surface

→ near shore fills with sedimetn form volcanic activity, fills any troughs or depression in the rust, and erosion is trying to fill up the lower spots