Marine Geo Final Review

When was the last major eustatic sea level?

20,000 years ago

What causes the greatest vertical eustatic sea level (water) change?

changes to glacial volumes

What is the periodicity of ridge spreading rates?

millions of years

Which stratal termination shows a sea level rise?

onlap

What changes in isotopes?

neutrons

How does the delta front coarsen?

It coarsens upward

What type of sediment is the prodelta made out of?

Fine mud and clay (it is the most Seaward environment)

What is ture of a mixed barrier island that is not true of a wave dominated barrier island?

large ebb tidal deltas

Why don’t wave dominated barrier islands have large ebb tidal deltas?

strong waves push sediments back toward the shore, preventing it from accumulating in offshore bodies

What happens to beach after storms?

they become flatter

Where do sandbars move during fairweather?

Onshore

What beaches does coarser sediments produce?

steeper beaches

What are the theories of barrier island formation?

• Emergence of offshore sandbars

• Breaching of elongated splits by storms

• drowning of coastal ridges

What are the processes involved with the landward migration of a barrier island?

• shoreline erosion

• overwash deposits

• windblown sediments

What features dissipate wave energy and funnel debris offshore along the seaward side of a coral bank?

spur and groove

What part of the atom is knocked out of its normal position in optically stimulated luminescence dating?

electrons

What is a good propert of an index fossil?

• easy to identify

• occured over a short period of time

• widespread

• dissolution resistant

What decay particle is produced by 2 protons and 2 neutrons?

Alpha particles

What is the most useful in studying earth’s interior?

meteorites

What drives deep ocean currents to sink?

• colder water temperature and greater salinity due to sea ice formation

What is the pelagic organic content of an ooze?

30%

What to unconformities result from?

erosion and non deposition

What clay indicates formation in warmer climate?

Kaolinite

Why is a biozone boundary slightly inaccurate?

• emigration

• immigration

• extinctions are not instantaneous worldwide

What provides the least information about the age of sedimentary layers?

lithostratigraphy

What is the unconformity formed by an erosional surfave between parallel sedimentary layers?

disconformity

Why do the Rocky Mountains have a lower gravity value than expected?

• mountain crust is made up of less dense material

• the mountains have thicker crust at the mountain’s due to root of crust extending into the mantle

What does not cause plate motion?

crustal uplift

What is not commonly used to determine direction of plate movement?

island arcs

The length of time for the Wilson Cycle is:

500 million years

The failed rift valley formed during initial rifting can help to explain:

large rivers

What helps to produce thicker deposits along passive margin shelves?

reef and diapirs damming sediments, and the cooling of crust causing subsidence

What does not help produce thicker deposits along passive margin shelves?

island arcs trapping sediment

What does not support that smaller individual chambers, rather than just one magma chamber underlies the ridge?

gabbro thickens at transform faults

Magma feeding ridges originates in the:

asthenosphere

What does not happen at subduction zones?

the subducting plate melts

What is the circumstances equatorial seawater formed in the cretaceous?

Tethys

What did not plat a role in producing glaciers near the artic and cooling the earth from the cretaceous Hot House?

freezing of sea ice

Reltive sea level change results from changes in __________ and _________.

plate tectonics and eustatic sea level

Changes in accomodation space and _________ may results in horizontal movement of the shoreline.

sediment supply

________ is the horizontal movement of environments landward

Retrogradtion

________ is no horizontal movement of environments but building vertically

Aggradation

________ is horizontal movement of environments seaward

Progradation

Name and describe the 3 milankovitch cycles

i) Obliquity - change in tilt of the poles

ii) Eccentricity - change in orbit from elliptical to more circular

iii) Precession - change in wobble of the earth’s rotation and the orbital ellipse

Given that the Milankovitch cycles can lower insolation values, ___________ is required fro glacial advance.

cold summers

What measures very short term sea level chanfe with sub cm accuracy?

Satelites

What identifies short-term sea level change with cm accuracy?

tidal gage stations

What are two types of sediment that are used to identify sea level change over the last millennia?

corals and stromalites

When water evaporated from the ocean in the tropics or subtropics, the water vapor is enriched with _____, and when the resulting precipitation falls, the remaining water vapor is enriched in _____.

16 O

Water vapor is transferred from the tropics to the poles through the hydrologic cycle. When this water vapor condencses and precipitates as snow on land in the polar regions and later recrystallizes as ice, this ____ enriched water becomes locked up in the ice.

16O

During glacial periods ,O18 ratiosn in oceanic shells _______.

increase

High stand

slow rise/stand still

• high, thick, layers

Transgressive

rapid rise

• very thing layer (usually underneath high stand layer)

Forced Regressive

fall

• usually almost vertical

Low stand

stand still/ slow rise

• lower than everything else, horizontal layer

While both form where rivers meet oceans, what is the primary difference in coastline shape that defines deltas and estuaries?

Deltas are like a protuberance of land in the ocean, and estuaries are more like a flooded river valley caused by a rise in sea level

How does bottom friction modify the delta fron sandbar and channel?

bottom friction slows the velocity of the river’s head as it enters a shallow basin that forces the sediment to settle and form a sandbar, this results in the lateral spreading of the water, splitting into multiple channels.

Describe two processes that increase mud deposits in the central part of an estuary.

• Flocculation - the charges of clay particles causes them to stick togehter which makes them heavier and sink

• Biological - organisms ingest fine sediments and poop them out, causing them to sink

What are the different stages of the cycle of a delta lobe?

i) sediment accumulation

ii) delta progradation

iii) abandonment

iv) transgression

v) barrier islands

vi) sholl

Why did most of the major deltas form around 7,000 years ago?

7,000 years ago, the rate of sea level rise was stable, which allowed sediment to accumulate and deltas to prograde

Why do wave dominated barrier systems have few inlets?

The waves set up longshore currents which brings the sand down the shoreline and fills the inlets

Explain why mixed wave-tide barrier islands have a drumstick shape. Identify the processes and geomorphic features involved.

As waves hit the barrier, they refract and cause sediment buildup around the end of the island which forms the “head” of the drumstick

• Larger ebb delta

• wave refraction

• local reversal in longshore current

• progradation at updrift end

While many barrier islands today are retrogradational, why can progradational barrer islands form during the current rising sea level?

If a river can supply sediment fast enough for the size of the accomodation space, sediment can build up seaward despite sea level rise

There are no tidal barrier islands because the tides produce ridges that are _______ to the shoreline

perpendicular

Define stratigraphy

the study and correlation of different strata

What are 3 producers of siliceous oozes?

1. Diatoms

2. Radiolarians

3. Coccolithophores

Decomposition formula

6O2 + C6H12O6 —> 6H2O + 6CO2 + energy

what are two deep currents in the atlanic ocean?

north atlanic deep water and antarctic bottom water

Explain how turbulence is maintained by turbidity currents:

turbidity currents cause the head to slow down, so the body moves faster and runs into the head, creating turbulence

Lysocline -

the depth in the ocean where the rate of calcium carbonate dissolution increases dramatically

What is the shallowest lysocline type?

pteropod

• made of aragonite

What is the middle lysocline type?

calcium

• made of calcite

What is the deepest lysocline type?

coccolithophore

• low magnesium

The CCD is the depth below which ______________

the rate of calcium carbonate dissolution equals the rate of supply

Explain why the CCD is shallower in the Pacific Ocean than the Atlanic Ocean

In the Pacific, the “older” water accumulates more CO2 from organic matter respiration, creating more acidic conditions that dissolve calcium carbonate at shallower depths thant the Atlantic

Suess effect is caused by ________

the burning of fossil fuels

DeVires effect is caused by __________________

solar variations

To correct for Suess and DeVires effect, 14C ages are correlated with these 3 things:

coral rings, tree rings, varves

Why do basalts on the seafloor have more Ar present when they initially form?

When they first form, they rapidly cool at the ocean floor, trapping gases before they can escape, which results in excess argon.

Basalts on the seafloor are not a closed system, so how are K/Ar dates used to date the seafloor?

They build a timeline of magnetic reversals on land, then match them with the magnetic stripes found on the ocean floor.

What are the 4 basic laws of stratigraphy?

1. Law of superposition - oldest layers on the bottom, get younger as you go up

2. Law of continuity - layers are the same, even if they are separated by a river, canyon, etc.

3. Law of cross cutting relationships - layers that cut through other layers must be younger than the layer it cuts through

4. Law of original horizontality - all layers were originally deposited horizontally

Name 2 event themes

1. tectonic processes

2. surface processes

A geoid is a surface of:

equal gravity

Earth’s shape causes variations of the radius at different _________.

latidude

Free air anomanly corrects for ______ between the measurement and the geoid

distance

The Bouger anomaly corrects for _______ between the measurement of the geoid

mass

What are two discontinuity boundaries?

Moho (near lithosphere)

Gutenberg (near asthenosphere)

A tectonic plate is:

a unit of lithosphere that moves as a unit

What is the very top layer of the earth made of

sediment

What is the second layer of the earth made up of

basalt

• pillow basalts

What is the thrid layer of the earth made up of

Gabbro

• plutons

What is the final layer of the earth made up of

periotite

• ophiolites

Sediment deposits _______ moving away from the ridge. Why?

thicken

• the farther away from the ridge, the more time to accumulate

Crustal depth ______ moving away from the ridge. Why?

increases

• as the crust cools, it becomes denser and sinks

Age of crust ______ away from ridge

increases

Why is there positive gravity value on the right side of the trench (under the island arc)?

the subduction zone creates a dense, thick, and physically elevated mass compared to the deep trench ocean floor

Why is there a gravity negative value at the trench?

the trench is deep, and has less dense water, causing gravity to be negative

Why is there a positive gravity value at the left side of the trench (opposite from the arc)?

the ocean floor pushes upward before it dives into the trench, creating heavy, dense rock closer to the surface, which creates stronger than normal gravity.

CONDITIONS IN THE CRETACEOUS!!!!!!

Global seaway

equatorial

CONDITIONS IN THE CRETACEOUS!!!!!!

North/South Temp. Gradient

less