Clicker Questions
The processes which break rock and minerals into smaller particles are collectively termed
weathering
Grains on the continental shelf are subject to erosion due to what?
How will bottom energy from waves change as you get farther away from the shelf?
Tides and wind generated waves and currents
As you get farther away from the shelf, depth increases so bottom energy decreases. The wave base only reaches down half the length of the wavelength so there is no wave energy below this point. In deeper water, the bottom is below the wave base.
The nature of the sediment at a certain place is determined by two factors
Particle size distribution of the material that comes in
Energy conditions at the site
What type of structure is found within a water molecule? (caused by the distribution of the ions)
What type of bonding is found between water molecules?
Dipole structure
Hydrogen bonding
What processes lead to variations in salinity?
evaporation increases salinity
ice formation increases salinity
freshwater runoff and precipitation decrease salinity
Under low energy conditions, which of the following would most likely be deposited?
Silt, Coarse Sand, Clay, Mud
coarse sand
What are the differences seen in sediment below the CCD for calcareous vs siliceous material?
siliceous material will be seen in the sediment below the CCD depth, but calcareous material will not because they dissolve on the sediment below the CCD.
Is a higher or lower velocity needed to erode mud grains? Why?
Then, when mud grains are in suspension is a low or high velocity current needed to keep them in transport?
A HIGH velocity is needed to erode mud grains because of "stickiness"
A LOW velocity current is needed to keep them in transport because of their small size and low density
What are two important properties of water?
1. High heat capacity
2. high solvent power
What is the three layer structure of the ocean based on density stratification?
Surface layer (2% of volume)
Pycnocline layer (18% of volume) constant in low latitudes due to constant heating, mid latitudes the pycnocline coincides with the halocline.
Deep layer (80% of volume), originates in high latitudes by cooling and sinking of surface water
What is the major reason water is such an excellent solvent?
It's dipole character
What is a low sedimentation rate versus a high sedimentation rate?
-Low sedimentation rate = a low supply of particles allows more time for the currents to sort the particles and you end up with a well sorted sediment
-High sedimentation rate = does not allow time to sort the particles and you'll end up with a poorly sorted sediment.
Will a low supply of particles (low sedimentation rate) lead to poor or well sorted sediment? Why
It will lead to well sorted sediment because it allows more time for the currents to sort the particles so you end up with a well sorted sediment where particles of different sizes are separated.
A high sedimentation rate does not allow time to sort the particles and you'll end up with a poorly sorted sediment
What are sinks? What are some examples?
The processes that remove salt from the water.
-Evaporation then precipitation
-Sea spray
-precipitated as organisms shells
-removal as fecal pellets
Why aren't the ionic compositions of rivers and oceans similar?
Residence time of the elements in seawater!
There is a high residence time for most abundant ions chloride and sodium because they have low geochemical and biochemical reactivity.
Lower residence time ions are more reactive like calcium since it is used for the growth of carbonate shells
With respect to sedimentation, particles on the continental shelf are subject to
redistribution by wind and tide generated currents
What are the five different classifications of sediment on formation?
Terrigenous- find and coarse grains produced by weathering and erosion of rocks on land
Biogenous sediment- fine and coarse grains that are derived from the hardest part of organisms such as shells and skeletal debris. Material is usually calcium carbonate or silica.
Hydrogenous- particles that are precipitated by chemical or biochemical reactions in seawater. Ex:manganese nodules or iron sulfide deposits
Volcanogenous- particles that are ejected from volcanoes
Cosmogenous- very tiny grains that originate from outer space. Tend to be mixed into terrigenous and biogenous sediment
What is bulk emplacement? What are some examples?
Bulk emplacement= build up of sediment on the edge of the shelf/slope moves downward due to gravity.
Examples:
Slumps= mass that slides down with no internal deformations
slurries= debris flows and mud flows that transport shelf sediment to the deep ocean floor. The internal structure is destroyed due to the mixing of the flow and most of the slurries are transported due to turbidity currents.
How is surface water temperature different different in temperate and polar regions?
How is deep water temperature different in temperate and polar regions?
Surface water is higher in the tropic regions and lower in the polar regions due to the amount of solar energy it gets.
Deep water remains uniformly cold across locations
What do the thermocline, pycnocline, and halocline show? How does each change with depth?
-Thermocline= boundary where temperature drops sharply
-Pycnocline= boundary where density drops sharply
-halocline= boundary where salinity drops sharply
As depth increases,
Temperature decreases
Density increases
salinity increases
So, if one leads to the other, why aren’t the ionic compositions of rivers
and oceans similar ?
Due to residence time
How do turbidity currents and slumping relate to submarine canyons?
Submarine canyons are mostly curved out by slumping and turbidity currents of river sediment and the canyon serves as a shute of the terrigenous mud and sand.
The turbidities form a deep sea fan when they reach the bottom of the canyon
What is relic sediment and why is most of the shelf composed of it?
Relic sediment= more coarse particles on presently deep sea floor because they were deposited in past conditions when sea level was lower.
Most of the shelf is composed of relict sediment because of the "rapid" rise in sea level so there was no time for the shelf sediment to retain the new steady state conditions.
What are the five broad categories of the constituents in seawater?
1. Major constituents- chloride and sodium make up the majority. Some other examples are sulfate, magnesium, calcium, and potassium. They are conservative ions
2. Nutrients- primary examples are phosphate, nitrate, and silicate. These are non conservative ions
3. Gases - inert gases (unreactive), carbon dioxide and oxygen which are used by organisms, and N2
4. Trace elements - very low concentrations in seawater such as magnesium and iron
5. Organic compounds - which are rather large compounds that were produced by organisms (excreted or leaked after death) Examples= lipids and proteins
Explain the oxygen profile in seawater. What is the significance of the 3 layers of seawater in this profile?
The oxygen concentration at the surface is high because of diffusion from the atmosphere. Then, there is the O2 minimum layer which occurs pycnocline layer because organic matter (food) get slowed down in this layer so respiration and decomposition are high here since organisms live in this zone. Then, the deep layers have oxygen because the deepwater comes from polar regions where the water was exposed to the surface so it got oxygen from the atmosphere