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Oceanography > Test 2 > Flashcards

Test 2 Flashcards

1
Q

What all does the study of plate tectonics involve?

A
  • Formation of plates
  • How they are formed
  • How they are destroyed
  • How they interact
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2
Q

What are tectonics?

A

The large scale processes affecting the structure of the Earth’s crust

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3
Q

What are the plates / plate groupings?

A

North American Plate
Australian Plate
Antarctic Plate
Caribbean Plate
African Plate
South American Plate
Indian Plate
Arabian Plate
Pacific Plate
Eurasian Plate

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4
Q

What are the three types of plate boundaries?

A

Divergent
Convergent
Transform

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5
Q

What is a divergent plate boundary?

A

Where two plates move away from each other (Oceanic - Oceanic) (Continental - Continental)

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6
Q

What is a convergent boundary?

A

Where two plates move towards each other; oceanic is denser and goes underneath the continental (Oceanic - Oceanic) (Continental - Oceanic) (Continental - Continental)

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7
Q

What is a transform boundary?

A

Where two plates slide horizontally past each other creating fault lines

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8
Q

What do seismic waves help to determine?

A
  • Location and thickness of plates
  • Some properties of earths internal structure
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9
Q

Primary (P) Waves

A

The fastest type of wave
Movement is parallel
Can pass through liquid outer core
slowed and refracted

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10
Q

What is the density of the inner core?

A

10.7g/cm3

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11
Q

Secondary (S) Waves

A

1-2 km/sec slower
Movement is at a right angle
Cannot travel through lower mantle; reflects off of it
Cannot pass through liquid outer core

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12
Q

What is the density of lower mantle?

A

4.5 g/cm3

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13
Q

Surface waves

A

Large motion waves
The waves you can feel

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14
Q

Lithosphere

A

Rigid upper mantle + crust “floats” on partially molten asthenosphere

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15
Q

Continental crust

A

Granite
Density 2.7 g/cm
35 km average thickness

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16
Q

Oceanic crust

A

Basalt
Density 3.0 g/cm
8 km average thickness

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17
Q

Moho discontinuity

A

The boundary between the Earth’s crust and its mantle, identified by a distinct change in the velocity of seismic waves as they pass through different densities of rock (1909)

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18
Q

Alfred Wegener

A
  • German meteorologist and geophysicist
  • Advanced the idea of mobile continents in 1912
  • Fitted the continents together
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19
Q

What was Wegener’s evidence?

A
  • Matching sequence of rocks and mountain chains of separate continents
  • Fossil evidence of different continents
  • Glacial deposits in unusual places
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20
Q

What did Frederick Vine and Drummond Matthews do?

A

Discovered seafloor spreading with magnetic “striping” pattern in the 1960’s

21
Q

Harry Hess

A
  • Geologist that published “History of Ocean Basins” in 1962
  • Discussed sea floor spreading in relation to convection of magma in mantle
  • New crust formed at ridges and old crust subducted at trenches
22
Q

What are specific geographic areas of the ocean delineated by?

A
  • Common landforms
  • Water conditions
23
Q

What are the three marine provinces?

A
  • Continental margin
  • Mid ocean ridges
  • Deep ocean basins (abyssal plains)
24
Q

What are the characteristics of a passive continental margin?

A
  • No plate boundaries
  • Produced by seafloor spreading (oldest crust)
  • Usually lack tectonic activity
  • Gradual slope
  • Wide shelf
25
Q

What are the characteristics of an active continental margin?

A
  • Narrow continental shelf
  • Steep slope
  • Deep offshore trenches
  • A lot of tectonic activity
  • Some type of plate boundary
26
Q

What are turbidity currents?

A

A turbidity current is a rapid, downhill flow of water and sediments caused by increased density due to high amounts of accumulated sediment (underwater avalanche of sediment that can be triggered by earthquakes, collapsing slopes, or other disturbances)

27
Q

What are turbidite deposits?

A

sedimentary beds of sediments caused by turbidity currents

28
Q

What are submarine canyons?

A

A submarine canyon is a deep, steep sided valley carved into the ocean floor caused by turbidity currents

29
Q

What are deep sea fans?

A

A deep sea fan is a large, fan shaped accumulation of sediment that forms are the base of the continental slope or on the continental rise

30
Q

What are the characteristics of mid-ocean ridges?

A
  • Entirely volcanic
  • Composed of basaltic lavas
  • Crest is a down-dropped rift valley
  • Hydrothermal vents
31
Q

Mid Atlantic Ridge

A
  • Largest mountain range on Earth
  • Spreading center of a divergent boundary
  • Extends 75,000 km
  • 1000 km average width
  • 2.5 km above seafloor average height
  • Covers 23% of Earth’s surface
32
Q

What are the five primary controlling factors for the distribution of ocean sediments?

A
  • Age of underlying crust
  • Tectonic history of the ocean crust
  • Structural trends in basement
  • Nature and locations of sediment sources
  • Nature of sedimentary processes delivering sediments to depocenters
33
Q

Classification of sediments by size of particles

A
  • Boulders and Cobbles
  • Pebbles
  • Sand (0.1 mm)
  • Silt (0.01 mm)
  • Clay (0.001 mm)
34
Q

What are the four possible origins of particles?

A
  • Lithogenous/terrigenous
  • Biogenous
  • Hydrogenous
  • Cosmogenous
35
Q

Where do cosmogenous particles come from?

A

Sediments that come from space and are a relatively minor source of ocean sediment

36
Q

What are manganese nodules? (Hydrogenous)

A
  • Round hard lumps of manganese, iron, or other metals
  • ~5cm diameter (up to 20 cm)
  • Found on deep ocean floor
  • 100 nodules/m squared
37
Q

Where do hydrogenous particles come from?

A

Metal-rich particles that come from hydrothermal vents eventually sink to the seafloor in the area surrounding the seafloor
- Iron and manganese
- copper, cobalt, lead, nickel, silver, zinc

38
Q

What are hydrothermal vents?

A

Discovered in the late 1970s, hydrothermal vents discharge heated water that does not contain oxygen but high concentrations of sulfides

39
Q

Silica and Calcium Carbonate Dissolution Rates:

A
  • Seawater is undersaturated with silica
  • Rate of dissolution of silica is slow at all depths but decreases even further with depth through the upper 2 km
  • Rate of dissolution of calcium carbonate is low near the surface but increases rapidly with depth
  • In deep water all calcium carbonate is dissolved
40
Q

Foraminifera (forams)

A

Marine
Calcium carbonate shells

41
Q

Coccolithophores

A
  • Phytoplankton
  • Mostly in subpolar regions
  • Made of calcite
  • 0.003 mm hubcap shape
42
Q

Radiolarians

A
  • Single cell
  • Among oldest protozoa
  • Planktonic
  • Silica shells
  • Rock formed: chert
43
Q

Diatoms

A
  • Single cell
  • 2 part silica cell walls
  • indicators of environmental quality
  • Rock formed: chert
44
Q

Where do biogenous particles come from?

A

Largely hard parts
- Calcareous (calcium carbonate)
- Siliceous
Accumulation rate dependent upon rate of production and rate of decomposition

45
Q

Where do lithogenous particles come from? (primarily silica)

A

The land through weathering and erosion

46
Q

Neritic Deposits

A

Derived from rocks from nearby landmasses
- Coarse grained
- Accumulate rapidly on continental slope, rise, and shelf
Ex.
- Beach deposits
- Turbidite deposits
- Glacial deposits

47
Q

Pelagic Deposits

A
  • Fine-grained
  • Accumulates slowly on ocean floor
  • Includes particles from volcanic ash and windblown dust
  • Abyssal clay
48
Q
A

Oceanography (3 decks)

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