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oceanography > Oceanography Midterm > Flashcards

Oceanography Midterm Flashcards

1
Q

What percentage of Earth’s surface is covered by ocean?

A

About 71% of Earth’s surface is covered by ocean.

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2
Q

Where is the deepest spot in the ocean, and how deep is it?

A

The deepest spot in the ocean is the Mariana Trench, which reaches a depth of approximately 36,000 feet (10,973 meters).

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3
Q

What is oceanography?

A

Oceanography is the study of the ocean, including its ecosystems, currents, and geology.

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4
Q

What is dead reckoning?

A

Dead reckoning is a navigation method used to estimate one’s current position based on a previously determined position, accounting for speed, time, and direction.

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5
Q

Why was the invention of a clock that kept accurate time at sea important for navigation?

A

The invention of an accurate clock allowed sailors to determine their longitude, which was crucial for precise navigation.

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6
Q

Why was the accurate navigation allowed by the new clock so important for early oceanography?

A

Accurate navigation enabled explorers to chart ocean currents and seabed features, leading to advancements in oceanography.

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7
Q

What is the Gulf Stream and why was it important that sailing captains knew its location?

A

The Gulf Stream is a warm ocean current in the Atlantic Ocean. Knowing its location was important for faster and safer navigation.

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8
Q

Who was Captain James Cook, and what were the primary purposes of his explorations (including charting the Oregon coast)?

A

Captain James Cook was a British explorer known for his voyages to the Pacific Ocean, primarily for mapping and scientific exploration.

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9
Q

Who was the naturalist on the 1831–36 Beagle expedition that studied the geology and biology of South America and the South Pacific?

A

Charles Darwin was the naturalist on the Beagle expedition.

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10
Q

Who was Matthew Maury?

A

Matthew Maury was an American naval officer and oceanographer known as the ‘Father of Modern Oceanography’ for his work in mapping ocean currents.

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11
Q

What expedition marked the beginning of modern oceanography?

A

The HMS Challenger expedition (1872-1876) marked the beginning of modern oceanography.

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12
Q

What is SONAR (or echo-sounding)?

A

SONAR (Sound Navigation and Ranging) is a technique that uses sound propagation to navigate, communicate, or detect objects underwater.

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13
Q

What is multibeam (or swath) mapping?

A

Multibeam mapping is a sonar technique that uses multiple beams of sound to create detailed maps of the seafloor.

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14
Q

What percentage of the ocean floor has been explored?

A

Approximately 20% of the ocean floor has been explored.

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15
Q

What is Alvin?

A

Alvin is a manned submersible used for deep-sea exploration.

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16
Q

What is an ROV?

A

An ROV (Remotely Operated Vehicle) is an unmanned underwater vehicle controlled from the surface.

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17
Q

What is an AUV?

A

An AUV (Autonomous Underwater Vehicle) is an unmanned underwater vehicle that operates independently.

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18
Q

What is NeMO?

A

NeMO (North East Pacific Observing System) is a network for monitoring underwater volcanic activity.

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19
Q

What is the Ocean Drilling Program?

A

The Ocean Drilling Program is an international research program that explores the Earth’s history and structure through drilling into the ocean floor.

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20
Q

What techniques were used to discover the large underwater landslides off the coast of Hawaii?

A

Techniques included sonar mapping and underwater photography.

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21
Q

Why do we have to use indirect observations rather than direct ones to see what is deep within Earth?

A

Direct observations are not possible due to extreme conditions and depths within Earth.

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22
Q

What are the two different types of earthquake waves?

A

The two types are P-waves (primary waves) and S-waves (secondary waves).

P-waves can travel through solids and liquids, while S-waves can only travel through solids.

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23
Q

How does Earth’s gravity field tell us that there must be very dense material inside Earth?

A

The strength of Earth’s gravity indicates the presence of dense materials in the interior.

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24
Q

How much denser is the mantle compared to the crust?

A

The mantle is approximately 3 times denser than the crust.

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25
Q

How much denser is the core compared to the crust?

A

The core is about 8 times denser than the crust.

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26
Q

How are meteorites useful for telling us what is deep inside Earth?

A

Meteorites provide clues about the composition and structure of Earth’s interior.

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27
Q

Describe the general properties and dimensions of Earth’s crust, mantle, and core.

A

The crust is thin and solid, the mantle is thick and semi-solid, and the core is dense and liquid (outer) and solid (inner).

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28
Q

What is the Nebular Hypothesis?

A

The Nebular Hypothesis is the theory that the solar system formed from a rotating cloud of gas and dust.

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29
Q

What caused Earth to differentiate into different layers?

A

Differentiation occurred due to the melting of materials and the sinking of denser materials to form the core.

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30
Q

How does the thickness and density of oceanic crust compare to continental crust?

A

Oceanic crust is thinner and denser than continental crust.

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31
Q

How do we know that Earth’s mantle is not an immobile solid?

A

Evidence from seismic waves and mantle convection indicates that the mantle is able to flow.

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32
Q

What is isostasy?

A

Isostasy is the equilibrium between the Earth’s crust and the underlying mantle.

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33
Q

Describe the parts of the continental margin.

A

The continental margin consists of the continental shelf, continental slope, and continental rise.

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34
Q

What is a submarine canyon?

A

A submarine canyon is a deep, steep-sided valley cut into the seabed of the continental slope.

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35
Q

What is an abyssal plain?

A

An abyssal plain is a flat, deep-sea floor area, typically found at depths of 3,000 to 6,000 meters.

36
Q

What is a seamount?

A

A seamount is an underwater mountain formed by volcanic activity.

Seamounts are important biologically as they provide habitats for diverse marine life.

37
Q

What is a deep sea trench?

A

A deep sea trench is a long, narrow, and steep-sided depression in the ocean floor.

38
Q

What is a mid-ocean ridge?

A

A mid-ocean ridge is an underwater mountain range formed by plate tectonics.

39
Q

What is the difference between a scientific theory and a hypothesis?

A

A scientific theory is a well-substantiated explanation of an aspect of the natural world, while a hypothesis is a testable prediction about the relationship between variables.

40
Q

What 4 observations led Wegener to propose his idea of Continental Drift?

A
  1. The fit of the continents. 2. Fossil evidence across continents. 3. Geological similarities between continents. 4. Paleoclimate evidence.
41
Q

What was the critical weakness of Wegener’s Continental Drift theory?

A

Wegener could not provide a convincing mechanism for how continents could move.

42
Q

How were mid-ocean ridges discovered?

A

Mid-ocean ridges were discovered through sonar mapping of the ocean floor during World War II.

43
Q

What is seafloor spreading?

A

Seafloor spreading is the process by which new oceanic crust is formed at mid-ocean ridges and gradually moves away from the ridge.

44
Q

Why does seafloor spreading create ‘magnetic stripes’?

A

Magnetic stripes are created as molten rock cools and solidifies at mid-ocean ridges, recording the Earth’s magnetic field at that time.

45
Q

What are subduction zones?

A

Subduction zones are areas where one tectonic plate is being forced under another plate.

46
Q

Why do earthquakes occur in bands around Earth?

A

Earthquakes occur in bands due to the movement of tectonic plates along plate boundaries.

47
Q

What is Plate Tectonics?

A

Plate Tectonics is the scientific theory that describes the large-scale movements of Earth’s lithosphere.

48
Q

What is the Plate Tectonic conveyor belt?

A

The Plate Tectonic conveyor belt refers to the continuous movement of tectonic plates driven by mantle convection.

49
Q

What is the difference between the lithosphere and the asthenosphere?

A

The lithosphere is the rigid outer layer of the Earth, while the asthenosphere is the semi-fluid layer beneath it.

50
Q

What is a divergent plate boundary? Give an example.

A

A divergent plate boundary is where two tectonic plates move apart. An example is the Mid-Atlantic Ridge.

51
Q

What is a convergent plate boundary? Give an example.

A

A convergent plate boundary is where two tectonic plates collide. An example is the boundary between the Indian Plate and the Eurasian Plate.

52
Q

What is a transform plate boundary? Give an example.

A

A transform plate boundary is where two tectonic plates slide past each other. An example is the San Andreas Fault.

53
Q

What are examples of the 3 types of plate boundaries on the west coast of the U.S.?

A
  1. Divergent: None directly on the coast. 2. Convergent: Cascadia Subduction Zone. 3. Transform: San Andreas Fault.
54
Q

At what rate do most tectonic plates move?

A

Most tectonic plates move at a rate of about 1 to 10 centimeters per year, adding up to several meters over a human lifespan.

55
Q

What 3 forces drive the tectonic plates?

A
  1. Slab pull. 2. Ridge push. 3. Mantle convection.
56
Q

What are some examples of places on Earth where new ocean basins are in the process of forming?

A

Examples include the East African Rift and the Red Sea.

57
Q

Describe the age progression of the Hawaiian Islands.

A

The Hawaiian Islands show a progression where the northwest islands are older and the southeast islands are younger.

58
Q

What is the hotspot hypothesis?

A

The hotspot hypothesis suggests that volcanic islands form over a stationary hotspot in the mantle.

59
Q

How can fixed hotspots be useful for telling us about the movement of tectonic plates?

A

Fixed hotspots provide a reference point to track the movement of tectonic plates over time.

60
Q

What are the possible consequences of a rising mantle plume developing a large head that reaches Earth’s surface?

A

Possible consequences include the formation of large volcanic provinces and significant geological upheaval.

61
Q

What are some possible atmospheric effects of volcanic eruptions?

A

Possible effects include ash clouds, changes in climate, and the release of gases like sulfur dioxide.

62
Q

How do the volumes of flood basalts compare to the volumes of recent eruptions such as Mt St Helens or Mt Pinatubo?

A

Flood basalts are significantly larger in volume compared to recent eruptions like Mt St Helens or Mt Pinatubo.

63
Q

What key events in life on Earth correlate with major eruptions such as the Deccan and Siberian flood basalts?

A

Major eruptions correlate with mass extinction events in Earth’s history.

64
Q

If a flood basalt occurred in the ocean, how would it affect ocean life?

A

A flood basalt in the ocean could lead to habitat destruction and changes in ocean chemistry, affecting marine life.

65
Q

What are ocean sediments, and what can they tell us about the past?

A

Ocean sediments are particles that settle at the bottom of the ocean, providing clues about historical environmental conditions and biological activity.

66
Q

Why is the ocean sediment record usually more complete than the on-land sediment record?

A

The ocean sediment record is usually more complete due to continuous deposition and less erosion compared to land.

67
Q

What causes the correlation between the size of a sediment particle and how far from shore it can be transported?

A

Larger sediment particles are heavier and require more energy to be transported, limiting their distance from shore.

68
Q

What are the 4 main sources of terrigenous sediments to the ocean?

A

The four main sources are rivers, wind, glaciers, and coastal erosion.

69
Q

Where do biogenic sediments come from?

A

Biogenic sediments originate from the remains of marine organisms, such as shells and skeletons.

70
Q

What causes the difference in preservation rate between calcareous and siliceous shells?

A

Calcareous shells dissolve more easily in acidic conditions, while siliceous shells are more resistant, affecting their preservation rates.

71
Q

What are the 3 main examples of hydrogenous sediments?

A

The three main examples are manganese nodules, phosphorites, and metal sulfides.

72
Q

What are volcanigenic sediments?

A

Volcanigenic sediments are formed from volcanic materials, such as ash and lava fragments, that are deposited in ocean environments.

73
Q

What are cosmogenic sediments?

A

Cosmogenic sediments are formed from cosmic processes, including the interaction of cosmic rays with the Earth’s surface.

74
Q

Why do volcanigenic sediments often serve as a useful time marker in sediments?

A

Volcanigenic sediments can indicate specific volcanic events, providing a chronological marker in sediment layers.

75
Q

What can ocean sediments tell you about the history of an area?

A

Ocean sediments can reveal past climate conditions, biological activity, and geological events.

76
Q

In a layered sediment sample retrieved by a coring device, how do you know which layer of sediment is youngest?

A

The youngest layer is typically at the top of the core sample, as sediments accumulate over time.

77
Q

How can looking for turbidites in sediment cores from off the coast of Oregon tell us about past earthquakes in the area?

A

Turbidites can indicate underwater landslides triggered by earthquakes, providing evidence of seismic activity.

78
Q

What can volcanic ash layers in sediments tell us about the history of an area?

A

Volcanic ash layers can provide information about past volcanic eruptions and their impact on the environment.

79
Q

How can sediments collected from the ocean bottom tell us about past life and conditions near the ocean surface?

A

Sediments contain fossilized remains and chemical signatures that reflect past biological activity and environmental conditions.

80
Q

What is paleoceanography?

A

Paleoceanography is the study of the ocean’s history and changes over geological time.

81
Q

What is the difference between weather and climate? Which one is better recorded by ocean sediments?

A

Weather refers to short-term atmospheric conditions, while climate is the long-term average. Climate is better recorded by ocean sediments.

82
Q

How can studying glacial ice tell us about the ancient atmosphere?

A

Glacial ice traps air bubbles that contain ancient atmospheric gases, providing insights into past climate conditions.

83
Q

Why is CO2 called a greenhouse gas?

A

CO2 is called a greenhouse gas because it traps heat in the atmosphere, contributing to the greenhouse effect.

84
Q

How does the atmospheric concentration of CO2 since the late 20th century compare to the previous 800,000 years?

A

The atmospheric concentration of CO2 has increased significantly since the late 20th century, reaching levels not seen in the previous 800,000 years.

85
Q

How does the average annual temperature over the last 100 years compare to that of the previous 900 years?

A

The average annual temperature over the last 100 years has increased compared to the previous 900 years.

86
Q

How can we use ocean sediments to reconstruct the past temperature history of the upper ocean?

A

Ocean sediments contain temperature-sensitive proxies, such as foraminiferal shells, which can be analyzed to infer past temperatures.

87
Q

Why does the 18/16 ratio of oxygen isotopes in shells tell us how much glacial ice was on Earth when those shells formed? What has this told us about the timing of glaciations in the past?

A

The 18/16 ratio indicates the volume of glacial ice; lower ratios suggest more ice. This has helped date past glaciations.

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