GEOL 2300 Final

What is sediment?

weathered/eroded and fractured material from parent rocks

How can sediment be classified?

grain size and origin/source

What is used to measure grain size?

Wentworth Scale

What is the order of grain size from smallest to largest?

clay, silt, sand, gravel/pebble, cobble, and boulder

What makes clay difficult to erode away?

it clumps together via electrostatic interactions

What process forms clay?

chemical weathering

Silt is _____ to transport

easy

Why is sand an important resource?

it is used for beach nourishment, tourism, and concrete

What is sand theft?

removing sand from one beach and adding it to another, typically for tourism reasons

What is gravel/pebble sourced from?

rock fragments that have a variety of shapes

Where is cobble found?

close to its sources, like mountain streams or shingle beaches

Boulders are ______ to transport and are found ______ to its sources

hard, close

Within each grain size, how can each be classified?

from very fine to very coarse

What is lithogenous sediment?

sediment produced by erosion of rocks on land through wind, water, life, and the freezing/thawing of ice

Lithogenous sediment is transported from ______ to ______

source, sink

What are the sources of lithogenous sediment?

volcanoes, deserts, mountains, and beaches

What is the sink of lithogenous sediment, and how does it get there?

the ocean; it gets there through rivers, wind, and glaciers

___% of sediment is transported through rivers

90

Of sediment transported through rivers, ___% of sediment comes from Asia and is transported to the Indian Ocean

80

What causes sediment load to vary throughout time?

climate and precipitation

Where is a lot of lithogenous sediment deposited?

near shore or coastal plains

What happens to the depocenter when the sea level rises? Sea level falls?

gets closer to the coast; gets farther from the coast

Why is sediment transport through glaciers important?

it carves sediment and glacial landforms

How does sediment move regarding glacial transport?

it moves along glaciers/meltwater, forming terminal moraines and outwash plains

Lithogenous sediment goes directly into the sea at ____ latitudes during glacial transport

high

Why is sediment transported through waves important?

it carves coastlines and contributes to erosion

Transporting lithogenous sediment through waves sorts grain sizes, but is influenced by _____________

coastal characteristics

Lithogenous sediment transport through waves varies depending on _______ and _______

climate and weather conditions (storm or no storm)

Why is sediment transported through wind important?

it assists in abrasion and deflation during erosion

Wind can only transport _____ grain sizes

small

What is the major source of sediment for wind transport that can influence tropical cyclones?

deserts

The time that sediment transported through wind spends in the atmosphere depends on ______

altitude

What do the Saharan dust layer and volcanic eruptions do?

prevent storms from forming and cooling

Lithogenous sediment transported through landslides has a ______ range

limited

Where does sediment transport by landslides occur and what increases the chances of landslides?

steep slopes; high precipitation

What are landslides triggered by and what can they trigger?

earthquakes and volcanoes; tsunamis

Where does biogenous sediment come from?

organisms

How do organisms create biogenous sediment?

by completing a lifecycle, having sloppy feeding, or producing fecal matter

What parts of organisms do biogenous sediment come from?

shells, tests, and calcareous/siliceous skeletons

The distribution of biogenous sediment depends on ____________

primary production

What can old CaCO3 shells be used for?

reconstructing temperature, salinity, and precipitation rates of the past

What are the types of calcareous organisms and what do they form?

foraminifera and coccolithophores; limestone for architecture

Where are siliceous organisms often found?

areas with terrestrial input

What are the types of siliceous organisms and what do they form?

radiolarians and diatoms; chert and diatomaceous earth used for prehistoric tools, filters, explosives, and agriculture

Does all biogenous sediment reach the seafloor, and why/why not?

no; dissolution occurs before they reach the seafloor (and can continue on the seafloor)

What causes dissolution of biogenous sediment?

seawater undersaturation in SiO2 and CaCO3

Where is SiO2 supersaturated/undersaturated in the ocean?

under: surface waters; super: with depth

Where is CaCO3 supersaturated/undersaturated in the ocean?

super: surface waters; under: with depth

Carbonate compensation depth is tied to ____, which is influenced by __________

pH; temperature

The CCD has net accumulation, where ______ = ______

input = output

What happens to sediment on an ocean ridge relating to the CCD?

it spreads and can go below the CCD

How does climate change influence the CCD and dissolution rates?

water is becoming more acidic, raising the CCD’s depth (making it shallower)

What happens when the CCD becomes shallower?

there is more space under the CCD for dissolution to occur, and organisms make weaker and thinner shells

What is acidification?

an increase the concentration of carbon dioxide, which lowers pH

During acidification, waters are _____saturated in CO3, _____ is being dissolved, and the depth of the CCD _______

under; more; decreases

In thermohaline circulation, older waters have a _______ concentration of CO2, therefore newer new water gains CO2 also

high

What causes older water to have high concentrations of CO2?

respiration ad decomposition

Hydrogenous sediment has ______ input than lithogenous or biogenous sediment

lower

Why is hydrogenous sediment rare?

undersaturation

Where is hydrogenous sediment found?

where other sediment is low, which is away from the coast and in the deep open ocean

What 5 things create hydrogenous sediment?

hydrothermal vents, undersea volcanoes, manganese nodules, carbonates, and evaporites

What are hydrothermal vents, and what do they depend on?

white and black smokers; temperature

How do hydrothermal vents function?

thin oceanic crust allows water to heat up via magma

What are hydrothermal vents rich in, and what happens when they come into contact with seawater?

dissolved metals and sulfur; they precipitate out

What drives cooling and oxidation for hydrothermal vents?

temperature; chemical reactions

Where do undersea volcanoes occur?

along convergent boundaries and in shallow waters

What are undersea volcanoes rich in?

sulfides

How do manganese modules form?

they precipitate onto a large particle slowly (like shark teeth)

Where do manganese nodules occur?

in the deep ocean

How do carbonates (limestone) form?

dissolved CaCO3 precipitates out of solution in places with high temperatures

Where are carbonates found?

tropical locations

Where do evaporites occur?

marginal seas, like the Gulf of Mexico/Mediterranean Sea

Where are evaporites currently happening?

the Red Sea and Persian Gulf

What are evaporites driven by, and what do they form?

evaporation as salts precipitate out of solution while seawater becomes oversaturated; salt domes

Where does cosmogenous sediment come from?

space

What happens to most cosmogenous sediment before reaching earth?

it burns up

Stony tektites are made of ______

silicates

Iron rich tektites are ________

magnetic

The amount of energy required to transport sediment is a function of ___________

grain size

What grain size needs the most energy to move?

boulders

What grain size is transported nearshore? Offshore?

sand; sand, silt, and clay

What happens when the energy moving sediment is reduced?

larger grain sizes settle from suspension and get smaller (small grain sizes remain unchanged)

What curve shows the relationship between grain size and velocity?

the Hjulström

The depositional environment of a sediment reflects the amount of ______

energy

What is an example of a high energy depositional environment? Low energy?

ocean; marsh

What are the transport mechanisms of sediment?

rivers, wind, and waves

What happens to grain sizes in the deep sea core?

they differ

What does a turbidity current come from?

underwater avalanches of sediment due to triggers like earthquakes

Turbidity currents export sediment from the ____________ to the ____________

continental shelf; abyssal plain

Turbidity currents move _____ and _____

fast; far

What happened during the 1929 Grand Banks earthquake?

a turbidity current and tsunami was formed from an earthquake near Newfoundland (that was felt in NYC) on a transform fault

Where are sediment accumulation rates highest and lowest?

near the coast; in the middle of the ocean

Where is sediment accumulation thickest?

where the crust is oldest

Sediment accumulation in the deep sea is made up of _______ and _______

oozes; clays

Sediment accumulation near the coast is made up of _______ and _______ sediment

terrigenous; glacial

What are shelf sediments?

zones of relict sediments created by changes in sea level

What is upwelling driven by?

winds and Ekman transport

What is needed for a full Ekman spiral?

uniform density, depth, and constant wind for one or more days

What is required of the upper layer/pycnocline for an Ekman spiral?

it needs to be well mixed and controls depth

What is Ekman transport?

the movement of water 90 degrees to the right of the wind in the northern hemisphere/left of the wind in the southern hemisphere