Geo Oce EXAM 2

Side scan sonar

"fish" instrument towed behind vessel that sends and receives signals; low frequency sound pulses bounce off seafloor to produce picture of seafloor using reflected (returned signals called backscatter

Dropstones

large stones that drop out of icebergs to seafloor

Strata

layer of rock

Lateral continuity

layers deposited in continuous expanses

Original horizontality

layers of sediment deposit first horizontally

Anticlines

limbs dip away from the hinge and the layers fold into a hill - linear fold

Synclines

limbs dip towards the hinge and the layers create a U shape - linear fold

Turbidite

lithified turbidity current sediments that can carve submarine canyons

Deep Sea Trenches

long narrow steep depression in seafloor that is created by subduction - very fine sediment - organisms adapted to high water pressure, cold temp and low food supply

Weak reflector

low density contrast such as water to mud - lighter line

Diatoms

phytoplankton (microalgae) that secrete silica shell (frustule) and are 0.002-0.2mm and are round (centric) to elongated (pennate) structures - make up siliceous ooze

Coccolithophores

phytoplankton (microalgae) with interlocking CaCO3 plates (coccoliths) to form sphere, are less than 0.1mm - make up calcareous ooze

Discoasters

phytoplankton with str-shaped CaCO3 test, are extinct, were 0.005-0.04mm - make up calcareous ooze

Shelf break

point at which angle of seafloor steepens at around 25-550m deep

Inclusions

(a fragment of another rock) a rock including an inclusion must be younger than the inclusion

Things to look for in sediment cores

- Composition shows changes in sediment source or color to see changes in specific minerals, organic matter, and organism remains - Grain size shows nature of deposition such as sand (higher energy) and clay (lower energy) - Layer thickness shows duration of deposition where thicker layers= longer time intervals and thinner layers= brief events like storm deposits

Linear fold symmetry

- Symmetrical; limb angles similar - Asymmetrical: limb angles dissimilar - Isoclinal: tight folds, limbs nearly parallel - Overturned: beds tilted past vertical - Recumbent: beds tilted much past vertical

How do we recognize faults in rocks and in the landscape?

- can create visible shifts in distinct layers of rocks where the layers are no longer continuous on both sides - displacement of natural and human made features - displacement on the fault that offsets ground surface creates a step that is called a fault scarp

Multicore advantages

- collects duplicates at a site at the same depth - provides material for multiple research projects - enables efficient sampling - can be done in deeper waters

Moored Seafloor sediment trap advantages

- data specific to habitat (reef) or source of sediment (river) - used in shallow or deep waters - relatively easy to recover

Sub-bottom seismic profiling uses

- identify and interpret geologic processes, geologic formations, area's geologic history, and biological features like reefs - assess for fossil fuel deposits - identify locations of geohazards like landslides

Gravity core advantages

- provides long record - comparable or longer than vibracores - can be done in deeper waters (100s of m)

Piston core advantages

- provides long record (longer or as long as gravity cores) - can be done in deeper waters (100s m deep) - piston mechanism helps sediment from being disturbed (compressed) in the core barrel

Push core advantages

- requires minimal equipment - provides longer records than multicores (not as long as vibra-, piston-, or gravity cores) - can be done in shallow or deeper waters

Vibracore advantages

- requires minimal equipment but more than a push core - provides relatively long record (longer than multi- and push cores) - can be done in waters up to ~200 ft depth - fairly simple - cost effective to operate

Multibeam Echo Sounder uses

- seafloor mapping habitats and geologic features - coastal management - navigation - locating objects - collecting backscatter from water column

Side scan sonar uses

- seafloor mapping habitats and geologic features - locating human made objects (ships and planes) - assessing for resources - geohazards, and infrastructure

Surface sediment trap advantages

- specific depths - specific areas - general areas - easy to recover from water

Free-drifting naturally buoyant sediment trap advantages

- specific depths - specific currents below surface - could cover broad area - works independent from a ship allowing for more data collection

Passive continental margins

- what: continental to oceanic transition with no active plate boundary - formation: ancient continental rifts that have flooded - tectonically active?: no - found: edges of continents - sediments: terrestrial sediments (sand, silt, clay sized grains) from land with grain sizes that get finer the further from the shore - reliefs: Wide shelf with relatively low relief

Active continental margins

- what: where oceanic and continental plates converge in a subduction zone - formation: subduction zone tectonically active?: yes - found: edges of continents on subduction zone - sediments: mix of terrestrial (sand, silt, clay), volcanic (pyroclastic debris), and deep-sea (silt and clay) - geologic features: Deep sea trenches and volcanic arches and accretionary wedges - reliefs: high relief and steep slopes

Two-way travel time ______. Select all that apply: A. Can be measured with a sub-seismic profiling device B. Is a direct measurement of depth to the seafloor C. Is the measure of time it takes for a signal to leave an echo sounder, hit bottom, and reflect back to the echo sounder D. Can be used to calculate depth to the seafloor

A. Can be measured with a sub-seismic profiling device C. Is the measure of time it takes for a signal to leave an echo sounder, hit bottom, and reflect back to the echo sounder D. Can be used to calculate depth to the seafloor

Turbidity currents: Select one or more: A. Deposit sediments in a way that the coarsest grains on are the bottom and grain size gets finer upwards B. Deposit sediments in a fan shape at the base of the continental slope C. Are relatively weak forces that cannot erode or carry a lot of sediment D. Creates graded beds E. Gain energy and momentum when the continental slope levels off

A. Deposit sediments in a way that the coarsest grains on are the bottom and grain size gets finer upwards B. Deposit sediments in a fan shape at the base of the continental slope D. Creates graded beds

Plastic deformation is more likely to occur than brittle deformation if: Select one or more: A. The rock is more flexible. B. Stress is applied slowly. C. The rock is brittle. D. The rock temperature is very hot. E. The temperature of the rock and the pressure applied to it are low.

A. The rock is more flexible. B. Stress is applied slowly. D. The rock temperature is very hot.

Numerical ages determined from radioactive decay tells us what about rocks? Select one or more: A. When a magma or lava cooled to create an igneous rock. B. When the parent rock of an metamorphic rock formed. C. When a sedimentary rock was lithified. D. The individual ages of sediment grains in sedimentary rocks. E. When a metamorphic rock cooled down and became stable again after metamorphosis.

A. When a magma or lava cooled to create an igneous rock. D. The individual ages of sediment grains in sedimentary rocks. E. When a metamorphic rock cooled down and became stable again after metamorphosis.

Features of deep ocean

Abyssal plains Seamounts Guyots Atolls Deep-sea trenches Abyssal hills

Three types of unconformities

Angular unconformity Non-conformity Disconformity

Types of Linear Folds

Anticlines Synclines Monoclines

Recognize eroded linear folds.

Anticlines- youngest rocks on outside Synclines: youngest rocks on inside

Side scan sonar ________. Select all that apply: A. Uses a high frequency of sound waves B. Provides wide coverage of the seafloor due to the angle of the beams C. Is sometimes referred to as a "whale" D. Emits two beams of sound waves E. Emits beams of sound waves at wide angles to the side of the device

B. Provides wide coverage of the seafloor due to the angle of the beams D. Emits two beams of sound waves E. Emits beams of sound waves at wide angles to the side of the device

What is an example(s) of a strong reflector? Select all that apply: A. Mud B. Rock C. Metal shipwreck

B. Rock C. Metal shipwreck

When we have a high reflectance on the sonar, why do we not collect anything in the ponar grab sampler? A. The seafloor is soft and has muddy (soft) sediment B The seafloor is hard, and there is no muddy (soft) sediment C. The seafloor is soft and has no muddy sediment

B The seafloor is hard, and there is no muddy (soft) sediment

A nonconformity: Select one or more: A. Occurs between sedimentary rocks where the rocks below were tilted before the unconformity developed. B. Is a contact representing a time when no sediment may have been deposited. C. Is a contact representing a time when erosion may have removed rock or sediment. D. Occurs when sedimentary rocks overlie igneous or metamorphic rocks. E. Occurs between parallel, horizontal sedimentary rock layers.

B. Is a contact representing a time when no sediment may have been deposited. C. Is a contact representing a time when erosion may have removed rock or sediment. D. Occurs when sedimentary rocks overlie igneous or metamorphic rocks.

During Monday's lab, what marine research methods did we use? Select all that apply: A. Multibeam bathymetry echo sounder B. Ponar grab samples C. Sonar D. Sub-bottom seismic profiling

B. Ponar grab samples C. Sonar D. Sub-bottom seismic profiling

With an isoclinal anticline fold: Select one or more: A. The oldest layers will be exposed on the outside of the fold when it is eroded. B. The limbs are nearly vertical and parallel. C. The fold is "laying down" - with the limbs horizontal to the Earth's surface. D. The oldest layers will be exposed on the inside of the fold when it is eroded. E. The limbs dip toward the hinge.

B. The limbs are nearly vertical and parallel. D. The oldest layers will be exposed on the inside of the fold when it is eroded.

Classification of biogenous sediments

Based on grain size: Macroscopic Microscopic

The principle of cross-cutting relations states that: A. Younger layers are on top B. Rocks are originally deposited horizontally. C. Features that cut across others must be younger than the features they are going through. D. Older layers on top E. A rock containing an inclusion must be younger than the inclusion.

C. Features that cut across others must be younger than the features they are going through.

Lysocline

CaCO3 dissolution increases

Use of sediment traps and collected data timespan

Collect sediment settling and accumulating on the seafloor over days, months or years - Used for determining how fast sediment accumulates, types of sediment present, types of microorganisms present

Ways folds can be created and define each

Compression- buckling through shortening of the layer Conform to reverse fault- when layers move up and over step shaped faults they must bend into folds Shear- one part of layer moves over another part to produce fold Conform to monocline- faulting at depth may push up a block of crust and cause overlaying beds to bend into a monocline

Regions of passive continental margins

Continental shelf Shelf break Continental slope Continental rise

How to assess mircoorganism species in sediment cores and what can they say about the site?

Count and identify species through a sediment core to determine their ecological preferences to reconstruct environmental conditions over time through the core

Interpretation of side scan sonar

Creates acoustic shadow if object on seafloor obstructs signal from reaching seafloor, can assess object size (human made objects have strong return and are highly reflective)

Using the equation to calculate two-way travel time and the known average speed of sound in water (consult your lecture notes), what is the water depth at a location where it takes 20 seconds for the sound waves to return to the device? A. 100,000m B. 5,000m C. 60,000m D. 15,000m E. None of the above

D. 15,000m

Change in sounding technology over time

Early method- drop weight over boat and measure how much rope was let out in Fathoms Now- more electronic and precise

Layers of flat (horizontal) lines of reflectors below the seafloor suggest: A. Abyssal hills B. A submarine landslide C. Deformed sediments D. Deep-ocean sedimentation E. A submarine canyon

D. Deep-ocean sedimentation

_______________ are conical seafloor features created by volcanism that do not break the sea surface. A. Atoll lagoons B. Guyots C. Abyssal hills D. Seamounts E. Volcanic islands with atolls

D. Seamounts

Two way travel time depth conversion

Distance (depth)= [velocity (sound) x time]/ 2

Types of Circular Folds

Dome Basin

Recognize erodes circular folds

Domes- oldest rock in center Basin- youngest rock in center

Surface grab samples can be used to _________. Select all that apply; A. Study the seafloor in shallow and deep environments B. Study current patterns based on where sediments of certain sizes are found C. Study the distribution of organisms living on the seafloor D. Study the distribution of seafloor sediments E. All of the above

E. All of the above

Sub-bottom seismic profiling _________. Select all that apply: A. Uses a high frequency of sound waves, B. Shows how sound reflects off of the seafloor , C. Shows how sound reflects off of buried sediment layers, D. Detects different layers due to their hardness (density), E. Measures the time it takes for the signal to hit the seafloor and return to the device F. All of the above

F. All of the above

Indirect methods such as sub-bottom seismic profiling are often the first step in a big research project because the methods are relatively cheaper and more invasive than most direct sampling methods. True/ False

False

On a backscatter image, white (bright) features represent soft surfaces like mud that cause the sound waves to bounce back strongly to the echo sounder. True/ False

False

Radioactive isotopes with long half lives are more useful for dating geological materials because they break down quickly into their daughter elements, which means that we can measure the ratio between parent and daughter elements for longer. True/ False

False

Reflectors are boundaries between different layers, where strong reflectors represent low density differences between layers. True/ False

False

The continental shelf will be wider on an active continental margin than it will be on a passive continental margin. True/ False

False

The principle of superposition states that each sediment layer gets progressively older as they go upward. True/ False

False, they get younger as they go upwards

2 main geologic structures

Faults Folds

Describe the distribution of terrigenous grain sizes, roundness, and sorting in the ocean based on the energy of the water transporting the grains.

Grain sizes are bigger and less round close to the shore as the high energy that picks them up is depleted. As you move offshore, the sediment is more fine grained and round from the low energy environment.

Anatomy of a fold

Hinge: line along which fold has greatest curvature Limbs: sides, least curvature Axial plane: imaginary place that runs through all layers of hinge and divides the fold in half

Explain how oxygen isotopes are preserved in foraminifera shells, and how those provide a proxy record for global climate over the geologic past

If there's more oxygen in the atmosphere/ ocean it'll be in the shells showing when the climate was warmer (more oxygen) and cooler (less oxygen)

What do isotopic dates tell us about the three different rock types?

Igneous: when the magma or lava cooled Metamorphic: when the rock cooled from metamorphic temperature Sedimentary: dates or individual grains NOT the time of lithification

How is the geologic time scale constructed?

It is divided into periods based on dominant forms of life as well as major geologic and biologic events - all the types of dating were used

Importance of half-lives in determining what method of dating to use

Long half-lives are better for measuring because they are more reliable than short ones

Two way travel time

Measure of time it takes for signal to return

Why is there interest in hydrogenous sediments?

Mining the minerals

Types of sediment cores

Multicore Push Core Vibracore Gravity core Piston core

Types of faults

Normal Reverse Strike-Slip

Explain how ratios of certain elements can be used to reconstruct ocean temperature over the geologic past. Give an example.

O16 remains on land trapped in ice and snow when the climate is cold. O18 is in higher concentration. O16 melts and returns to the oceans when the climate is warmer. O18 concentration is lower.

5 Principles of Relative dating

Original horizontality Superposition Lateral continuity Cross-cutting relations Inclusion

Characteristics of mid-ocean ridges

Pillow basalt Sheeted dikes Hydrothermal Vents

Three factors that determine the distribution of microscopic biogenous sediments

Production Dissolution Dilution

Why do we correlate vertical series of rock layers?

Provide a record of location's geologic history

Where are hydrogenous sediments found?

Seafloor

Types of biogenous ooze

Siliceous ooze Calcareous ooze

Ways to correlate vertical series of rock layers

Stratigraphic correlation Lithologic correlation Fossil correlation

Paleooceanography

Study of oceans in geologic past with aim to reconstruct physical, chemical, or biological conditions such as ocean circulation, seawater chemistry, sea level/ water depth, patterns of sedimentation, biodiversity/ biogeography

Types of sediment traps

Surface sediment trap Free-Drifting Naturally-Buoyant sediment trap Moored Seafloor sediment trap

Two types of cosmogenic sediemtns

Tektites Microtektites

Five types of sediments on bottom of oceans

Terrigenous Hydrogenous Volcanic Cosmogenic Biogenous

Sediment size in the ocean gets progressively finer the farther out into the ocean you go. This is because the coarsest sediments are deposited when rivers and deltas hit the ocean, lose energy, and drop the largest (heaviest) grains. True/ False

True

Sonar determines the depth to the seafloor or objects in the water by the use of reflected sound waves. True/ False

True

Surface grab samples do not provide the same long-term temporal perspective of sedimentation as do sediment cores. True/ False

True

Why might a rock be more likely to deform plastically versus brittlely?

They are more likely to deform plastically under high temp and pressure, if the rate of stress application is slower, and if the rock is a more flexible type.

Why is it useful to know how the global climate and ocean characteristics (temperature, salinity, sea level) have changed over geologic time (over millions of years)?

To predict future patterns an asses human impacts on pre-existing patterns

A multiple refers to a very strong reflector that gets repeated in the subsurface in a sub-bottom seismic profile. It is an artifact of the strength of the reflector, not evidence for multiple strong reflectors below the seafloor. True/ False

True

Abyssal plains are composed of sediment layers that can be very thick (greater than 100's of meters thick) and that overlie oceanic crust made of basalt. True/ False

True

Backscatter refers to waves that reflect of of the seafloor, are received by the echo sounder, and produce a grayscale image of the seafloor. Select all that apply: True/ False

True

Both sheeted dikes and hydrothermal vents are created by the formation of fissures (cracks) in oceanic crust as the crust accommodates the tension of the oceanic plate pulling apart. True/ False

True

By correlating rock types, fossils, and their vertical succession we can determine the relative ages of rock layers (strata) and formations (groups of similar strata). True/ False

True

Normal faults form from a force called tension that causes a the thinning and extension of the crust, while reverse faults form when compression squeezes and shortens the crust. True/ False

True

Ponar sediment grab samples collect the upper ~20 cm of the seafloor, which may include living and dead organisms, sediments, plants, and human debris. True/ False

True

Uses and advantages of surface samplers

Uses: - studying surface sediment and composition - sediment distribution to indicate currents - living/ dead organism diversity - plants and invertebrate animals Advantages: - helpful in murky/ deep waters - come in various sizes so ship size can vary

Relative Dating

Using methods to determine the time of which one geologic event happened with respect to others

How are hydrogenous sediments created at hydrothermal vents?

Water heats up in cracks dissolving minerals in crust- water comes up to seafloor surface and cools, minerals precipitate due to changes in temp

Seamounts

abyssal mountains that DON'T reach sea surface - extinct volcanoes so sediments reflect that - house marine life on the slopes due to proximity to sunlight

Guyots

abyssal mountains with flat tops - extinct volcanoes that reached sea surface and got eroded by waves and then subsided below sea level - sediment is fine and volcanic - high diversity of life due to currents, nutrients, and habitat structure

Tephra

ash distributed by wind

Strong reflector

big density contrast such as water to rock - darker line

Low backscatter

black, weak return, reflection off softer sediments like sand and mud

Reflectors

boundaries between different layers

Contact

boundary between 2 formations

Elastic deformation

changes in shape that can be reverse by removing stress

Use of sediment cores and collected data timespan

collect 10s of cm to several meters of seafloor sediments from hundreds to millions of years

Use of surface samplers and collected data timespan

collect upper 20-50cm of sediment on seafloor (years to 1000s of years)

Biogenous sediments

composed of dead marine organisms parts

Calcareous ooze

composed of organisms that have skeletons made of calcium carbonate (coccolithophores, discoasters, foraminifera)

Siliceous ooze

composed of organisms that have skeletons made of silica (diatoms and radiolarians)

Microscopic biogenous sediments

composed of very small whole or fragmented organisms (less than 1mm) - ex. unicellular algae or protozoans - more common - create oozes

Three major marine provinces

continental margins, deep-ocean basins, mid-ocean ridge

Lithologic correlation

correlating strata by physical characteristics of rock type

Tektites

created when terrestrial sediments are melted and ejected from meteorite impact sites (gravel-sized, glassy bodies, black, green, brown, gray)

Turbidity currents

dense, rapid downslope flow of water and sediment triggered by earthquakes and unstable slopes - lose energy when slope starts t level off

Volcanic sediment distribution

deposition high near volcanoes but slows as you move away from source - grain size decreases with increasing distance from volcano

Carbonate Compensation Depth (CCD)

depth where CaCO3 dissolves completely

Numerical dating

determining the age of rocks in years before present

Echo sounder

device for determining depth to seafloor or objects in the water by emitting a sound wave signal into water and measures time it takes for wave to return

Isotopes

different versions of an element with different atomic masses (different number of neutrons)

Pumice

distributed through oceans by floating in the water

Terrigenous water transport

distribution onshore-offshore is a function of water energy as distance from shore increases - water energy decreases with grain size - fluvial sediment input - occurs around edges of continent

Abyssal hills

domed or elongated hills formed by faulting and volcanism - rise up around 1000m above sea floor but are not as tall as seamounts - sediment is volcanic

How is numerical dating done?

done through radiometric dating of isotopes half-lives to see the amount of decay

Superposition

each layer of sediment must be younger than the one below it

James Hutton

father of geology and the one who founded the idea of uniformitarianism

Hydrothermal vents

fissures in crust associated with MORs where water get superheated and infused with elements, minerals precipitate as water cools - mineral build up creates habitat structure: unique diversity of organisms that vary spatially with resources

Deep Ocean

flat expanse of sea floor, depth of over 3000m, between continental margins and MOR

Dome

fold in shape of overturned bowl - circular fold

Basin

fold in shape of upright bowl - circular fold

Plunging folds

fold with horizontal hinge

Non-plunging folds

fold with tilted hinge

Fault

form through brittle deformation

Fold

form through elastic/ plastic deformation

Cosmogenic sediments

formed or created by extraterrestrial sources with very low accumulation rates

Free-drifting naturally buoyant sediment trap

free-floating drifts down to certain depth and collects data with a current

Surface sediment trap

free-floating or tethered to a ship collects data a specific depth, moves with surface current or ship

Uncomformities

gaps in the rock record, it is a contact representing a period of non-deposition and possibly erosion

Terrigenous ice transport

glaciers carry poorly sorted sediment and the material drops out as ice metals - ice raft debris - dropstones

Formations

groups of strata with a specific rock type that represent a distinct interval of sediment deposition

Normal Fault

hanging wall goes down relative to footwall - divergent zones - tension force

Reverse Fault

hanging wall goes up relative to footwall - convergent zone - compression force

Sub-bottom seismic profiling

high frequency profiling that penetrates below seafloor reflecting off seafloor and buried sediment layer - detects different layers due to differences in hardness (density) of materials - uses strength of reflectors to produce images

Half-life

how long it takes for half a group of atoms to decay (measure ratio of parent to daughter in mineral to calculate age)

Crusts

hydrogenous sediment that occurs at a hydrothermal vent and is in deep ocean basins precipitating minerals form layered crust on seafloor - form where sedimentation is very low because otherwise nodules would be buried and stop forming

Hydrogenous nodules

hydrogenous sediment that occurs at a hydrothermal vent and is rounded lumps of manganese and other metals like iron, copper, cobalt, and nickel that form around central object like a shell of rock; concentric layers slowly deposit over it and form over millions of years

Cross-cutting relations

if 1 geologic feature cuts across another then the one that has been cut is older

Sheeted dikes

igneous intrusions travel upwards through fractures in ocean crust, melt cools below seafloor creating nearly parallel, nearly vertical series of intrusions (sheet-like)

Continental Rise

incline where the continental slope meets the crust and represents the transition between continental slope and deep-ocean - sediment is a continuation of deposition from turbidity currents creating graded bed containing sand silt and clay - deep-sea environment with no sunlight and low productivity

Biogenous ooze

made of microscopic biogenous sediments and clay - classified by composition - formed by accumulation by currents and sinking to seafloor

Macroscopic Biogenous Sediments

made of whole and fragmented marine organisms (greater than 1mm) - less common than microscopic because high concentrations of macroscopic organisms are less common - ex. CaCO3 producing organisms that have a shell (corals, shells, sea stars, urchins, shark teeth) - abundant in shallow marine settings due to abundance of CaCO3 producing organisms

Radioactive decay

measuring an atom's half-life

Radiometric dating

measuring ratios of radioactive elements and decay products to calculate a number age

Microtektites

microscopic tektites (mm), glassy, yellow-brown

Production

more biogenous sediment below areas of high primary productivity than areas of low PP

Multibeam Echo Sounder

multiple simultaneous sound waves (beams) deployed in fan-shape to produce data through backscatter to show depth plotted as bathymetry 2D or 3D map - red= shallow - blue/ purple= deep

Indirect Research Methods

no physical samples collected - data is just recorded and analyzed - noninvasive - fast - cost-effective

Push core

one core at a time (10s cm long) taken manually or with ROV

Piston core

one core at a time (10s m) by piston core barrel helping transfer force of fall into pushing core barrel farther into the sediment, long heavy and awkward and requires specialized ship

Gravity core

one core at a time (m to 0sm long) by large weight on core barrel pushing it into sediment by force of gravity (not motor) dropped from side of ship but heavy and awkward to deploy, requires a boat with a winch

Vibracore

one core at a time (m to 10s of m) by motor attached to core barrel and vibrations from the motor drive the core barrel into the sediment (taken manually or by boat with rig)

Continental margin

outer edge of continental crust and adjacent to oceanic crust under the sea level (shelf break, break, slope, rise) - active or passive

Volcanic sediments

particles ejected from volcanoes (ash and lapilli)

Uniformitarianism

physical processes operating in modern world also operated in the past at roughly the same rates

Direct Research Methods

physical samples collected - usually occurs after indirect methods - invasive - more time required - more costly

Proxies and an example

physical/ chemical parameter that can be measured and calibrated to interpret past conditions - ex. Shells/ skeletons of marine organisms accumulate in seafloor sediments as they die leaving only the hard parts and they're collected through sediment cores

Sounding

process of measuring depth of ocean

Isotopic decay

process that changes atomic number, so changing an atom of one element to another

Hydrogenous sediments

produced by chemical reactions and mineral precipitation through changes in water temp, pressure, or pH

Uses of sediment cores

provide long-term record over time - geologic sediment type changes - environmental effects like water energy and marine setting changes - biologic such as habitat or biodiversity changes - climate such as seawater temp or global ice volume changes

Authigenic sediments

refers to sediments that form in the place they're found on seafloor - hydrogenous sediments is a type because they are not created and transported somewhere else

Backscatter

reflected (return) signals that create picture of seafloor

Stratigraphic correlation

relating strata at different locations

Dilution

relative proportions of different sediment types with different distances from land - coastal areas have more terrigenous sediment that dilutes biogenic matter - terrigenous are less abundant offshore so biogenic sediments will be more abundant

Disconformity

rocks below unconformity were NOT tilted or folded before erosion (formation: deposition🡪erosion🡪deposition)

Angular unconformity

rocks below unconformity were tilted/folded before the unconformity developed (formation: deposition🡪deformation🡪erosion🡪renewed deposition)

Mid-Ocean Ridges

seafloor spreading centered with rift valley and continuous volcanic ridge - found in the mid-Atlantic - volcanic rocks (basalt) with very fine sediment over it

Ice raft Debris

sediment transported to ocean by icebergs and falls to seafloor as ice melts

Non-conformity

sedimentary rocks overlay older igneous or metamorphic rocks that were eroded. (Formation: igneous rocks form🡪igneous rock erodes🡪sedimentary rocks deposit)

Accretionary wedge

sediments scraped onto non-subducting plate from surface of subducting plate in a wedge shape

Continental Shelf

shallow, flooded edge of continent - terrestrial sediment from rivers and deltas with coarse grains in the high energy environment and the fine grains in low energy - have diversity because of the nutrients and sunlight that supports plant life - habitat changes as sunlight changes with depth - coral reefs present

Hjulstrom Curve

shows relationship between particle size and energy needed to erode, transport, and deposit sediment

Monocline

single linear fold that looks like a stair step and usually forms on a fault scarp - deforms when fault slips

Continental slope

slope between shelf break and deep ocean floor - sediments are shelf sediments transported downhill by turbidity currents (sand silt and clay) - sediment deposits in a fan shape at the base of the slope and settles out by size which creates a graded bed - submarine canyons may be here - less productive environment because of low sunlight and the slope is unstable, but the diversity is high even when abundance is low - canyon walls provide habitat

Moored Seafloor sediment trap

stationary on seafloor near area of interest

Structural geology

study of form arrangement and internal structure of rocks and how rocks deform in response to stress

Topography

study of forms and features on land surfaces

Pillow basalt

surface of extruding lava cools quickly, while hot subsurface continues to flow (round ~1m diameter)

Multicore

takes multiple short cores at once, deployed from ship

Bathymetry

topography of the ocean floor

Terrigenous sediments

transported to ocean from land by rivers, ice, wind; produced by weathering and erosion of rocks on land; typically sands, silts, and muds

Terrigenous wind transport

transports very fine sediments like dust (clay, minerals, quartz, feldspars, pyroxene or terrestrial biological grains (diatoms, spores, pollen) - well-sorted sediment - can travel very long distances - higher levels of wind transported sediments in ocean near deserts depending on wind patterns

Strike-Slip Fault

two plates slide by each other - transform - shear stress

Fossil correlation

using fossils to define relative ages of strata that what contain them

Abyssal Plains

very flat region, years of sedimentation - found throughout ocean seafloor - sediments are very fine silt and clay - marine life organisms are spread out with no sunlight and dependent on limited food sources

Atolls

volcanoes that have sunk and coral reefs form around it and volcano is fully submerged into lagoons - volcanic sediments - high diversity of life due to surface and coral reef

Dissolution

water depth - silica dissolves in warm surface waters and accumulates in cold deep waters - carbonate dissolves in cold acidic waters and accumulates in warm surface waters

Plastic deformation

when enough stress is applied to a rock that it permanently changes its shape without breaking it (creates folds)

Brittle deformation

when rocks break rather than bend (creates faults)

Graded beds

when sediments go from course to find going upwards

High backscatter

white, strong return, reflection off hard surfaces such as rock

Radiolarians

zooplankton (protozoa) that secret silica shell (test), 0.1-0.2mm, and have elaborate globular shells with holes - make up siliceous ooze

Foraminifera

zooplankton with chambered CaCO3 shell (test), are less than 1mm - make up calcareous ooze