Chapter 1: The Physical Structure of Oceans
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Questions and Answers

What are submarine ridges primarily associated with?

  • Areas where continental crust is lost
  • Tectonic plate separation (correct)
  • Locations of ancient ocean floors
  • Regions of high seismic activity

What is the lithosphere composed of?

  • Partly molten asthenosphere
  • Liquid mantle material
  • Cracked sections of the Earth's crust (correct)
  • A thick layer of magma

What drives the movement of tectonic plates?

  • Gravitational forces from the Moon
  • The cooling of the oceanic crust
  • A complex flow of thermal energy in the mantle (correct)
  • Variations in sea level

How does new crust form at ocean ridges?

<p>As basalt from the asthenosphere cools on contact with seawater (C)</p> Signup and view all the answers

What occurs at ocean trenches?

<p>Old crust is lost (C)</p> Signup and view all the answers

What marks the line of division at ocean ridges?

<p>A depression or rift valley (B)</p> Signup and view all the answers

What is the estimated range of spreading rates of tectonic plates?

<p>Less than 1 cm to 16 cm per year (B)</p> Signup and view all the answers

Which type of tectonic plate only carries ocean floor?

<p>Oceanic plates (C)</p> Signup and view all the answers

What primarily affects the composition of the seabed?

<p>Bottom current speed (C)</p> Signup and view all the answers

Which of the following factors influences the type of sediment found on the ocean floor?

<p>Speed of the bottom current (A)</p> Signup and view all the answers

According to Stokes’s Law, what primarily determines the settling velocity of particles?

<p>The size and density of the particle (C)</p> Signup and view all the answers

What is commonly found on the shallow water seabed due to tidal currents and waves?

<p>Uncovered rock (A)</p> Signup and view all the answers

Which condition leads to finer sediments being more likely to remain suspended in the water column?

<p>Slower water movement (B)</p> Signup and view all the answers

What happens to sediment transport when the speed of bottom current exceeds the settling velocity of particles?

<p>Sediment transport increases rapidly (B)</p> Signup and view all the answers

Where is rock commonly uncovered on the ocean floor?

<p>On steep oceanic ridges and trenches (B)</p> Signup and view all the answers

What is primarily true about the majority of the ocean floor's coverage?

<p>It is predominantly covered in soft sediments (B)</p> Signup and view all the answers

What material primarily composes diatom ooze?

<p>Diatom fragments (A)</p> Signup and view all the answers

Where does radiolarian ooze predominantly occur?

<p>Between depths of 4000 and 8000 m in tropical oceans (C)</p> Signup and view all the answers

What is the primary composition of red clay found below 6000 m in the ocean?

<p>Fine-grained quartz and clay minerals (A)</p> Signup and view all the answers

What characterizes the accumulation rate of red clay compared to organic oozes?

<p>Red clay accumulates significantly slower than organic oozes. (D)</p> Signup and view all the answers

What defines the size of polymetallic nodules found on the ocean floor?

<p>1 mm to 15 cm in diameter (D)</p> Signup and view all the answers

Which metal is not commonly found in polymetallic nodules?

<p>Zinc (B)</p> Signup and view all the answers

What process primarily contributes to the formation of red clay sediments in the ocean?

<p>Aeolian fallout (D)</p> Signup and view all the answers

What depth range is mentioned as the area where polymetallic nodules are abundant?

<p>4000 to 6000 m (D)</p> Signup and view all the answers

What recent discoveries have changed the perception of the seabed?

<p>It was originally believed to be flat and featureless. (A)</p> Signup and view all the answers

What is the significance of the Kaikoura Canyon?

<p>It supports a high biodiversity and biomass. (A)</p> Signup and view all the answers

How deep is the Kaikoura Canyon?

<p>1000 meters (B)</p> Signup and view all the answers

What major geographic feature divides the Atlantic Ocean?

<p>The Mid-Atlantic Ridge (D)</p> Signup and view all the answers

What unique characteristic is associated with canyons like Kaikoura?

<p>They create complicated hydrographic conditions. (D)</p> Signup and view all the answers

What is a significant biological feature of the Kaikoura Canyon?

<p>It harbors a biomass 100 times higher than many deep-sea habitats. (D)</p> Signup and view all the answers

When were the major chains of mid-ocean ridges fully appreciated?

<p>During the 1950s and 1960s (B)</p> Signup and view all the answers

What feature defines the major chains known as mid-ocean ridges?

<p>Wide mountain ranges (D)</p> Signup and view all the answers

What regulates deep seabed mining outside individual country jurisdictions?

<p>International Seabed Authority (B)</p> Signup and view all the answers

Which of the following conditions allows organic material to become buried and eventually form oil and gas deposits?

<p>Anoxic conditions (B)</p> Signup and view all the answers

What are the potential long-term effects of mining nodules on marine populations?

<p>Habitat destruction (A)</p> Signup and view all the answers

In which era were most oceanic oil and gas deposits formed?

<p>Mesozoic (B)</p> Signup and view all the answers

What is considered the most promising area for commercial extraction of polymetallic nodules?

<p>Clarion Clipperton fracture zone (C)</p> Signup and view all the answers

Which process leads to the formation of nodules from low-oxygen pore water?

<p>Diagenetic (A)</p> Signup and view all the answers

What is the primary organic matter that contributes to oil and gas deposits in the ocean?

<p>Dead phytoplankton (B)</p> Signup and view all the answers

What is the typical average growth rate of polymetallic nodules over a million years?

<p>10-20 mm (A)</p> Signup and view all the answers

What materials can trap gas and oil beneath the surface?

<p>Salt or shales (B)</p> Signup and view all the answers

What material often serves as the nucleus for the formation of nodules?

<p>Fish teeth or whale ear ossicles (D)</p> Signup and view all the answers

Which organisms are particularly associated with the nodule areas in deep-sea environments?

<p>Anthozoans and sponges (C)</p> Signup and view all the answers

What is a common method used by scientists to collect seabed sediment samples?

<p>Core drilling (D)</p> Signup and view all the answers

What dual factors contribute to the variation in the chemical composition of nodules?

<p>Geographical location and depth parameters (D)</p> Signup and view all the answers

What type of spectroscopy can be used to analyze the detailed structure of nodules?

<p>Absorption spectroscopy (A)</p> Signup and view all the answers

How long does it typically take for nodules to form?

<p>Several million years (C)</p> Signup and view all the answers

What role do colloidal particles play in the formation of nodules?

<p>They facilitate the precipitation of metal ions. (B)</p> Signup and view all the answers

Flashcards

Tectonic plates

The rigid, moving pieces of Earth's lithosphere.

Ocean ridges

Vast systems of volcanic mountain chains that cross the ocean floor, marking the boundaries of tectonic plates.

Mid-ocean ridges

Major mountain chains found in the Atlantic, Indian, and Pacific Oceans, running roughly north-south.

Ocean ridges

Lines where tectonic plates separate, creating new crust.

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Ocean trenches

Form where tectonic plates collide, resulting in crust loss.

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Mid-Atlantic Ridge

A specific mid-ocean ridge that runs from the Arctic through Jan Mayen Island and Iceland, and south to 55° S.

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Seamounts

Submarine mountains that are part of larger volcanic systems.

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Sea-floor spreading

The process of new crust formation at ocean ridges.

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Submarine canyons

Deep, narrow valleys that cut through the continental slope, linking the shelf with the deep ocean.

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Lithosphere

Earth's outermost, rigid layer.

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Kaikoura Canyon

A specific submarine canyon located off the east coast of New Zealand's South Island, famous for high biodiversity and biomass.

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Asthenosphere

The layer below the lithosphere, partly molten and dense.

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Tectonic plates

Large sections of the Earth's crust that are in motion.

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Rift valley

A depression found along the center of ocean ridges.

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Tectonic plate movement

Continents and ocean areas are moved due to tectonic plate motion.

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Bathymetry

Measurement of the depth of the sea floor.

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Seabed Composition

The sea floor's composition varies greatly, from soft sediment to hard rock, depending on factors like current speed and particle size.

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Soft Sediments

The most common type of ocean floor material, generally composed of tiny particles that settle slowly.

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Strong Bottom Currents

Ocean currents that are strong enough to remove sediment particles from the bottom, uncovering rock.

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Sediment Type Variation

The type of sediment deposit on the ocean floor depends on the speed of the bottom current, and the size and density of suspended particles.

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Sediment Settling Velocity

The speed at which sediment particles settle to the ocean floor, influenced by size and density.

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Stokes's Law

A mathematical equation that predicts the settling velocity of small spherical particles in a fluid.

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Ocean Sediment Age

The thickness of ocean sediments can be roughly related to their age based on settling velocity under steady-state conditions.

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Continental Shelf

The gently sloping part of the ocean floor that extends from the shoreline out to the deep ocean.

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Diatom Ooze Composition

Diatom ooze is primarily made of diatom fragments, which are siliceous (made of silica).

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Diatom Ooze Location

Diatom ooze is found in a band around Antarctica and parts of the North Pacific. This distribution relates to the Antarctic convergence.

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Radiolarian Ooze Composition

Radiolarian ooze contains numerous radiolarian skeletons and occurs in tropical parts of the Pacific and Indian Oceans, and Atlantic.

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Red Clay Composition

Red clay is a deep-sea sediment primarily composed of fine-grained quartz (silica) and clay minerals, with amounts of iron, calcium, magnesium compounds and trace metals.

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Red Clay Origin

Red clay is mostly formed from aeolian fallout (wind-blown dust).

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Deep-Sea Nodules Location

Polymetallic nodules are found on or within the top few cm of the deep-sea floor at depths greater than 2000 meters and particularly between 4000 and 6000 meters.

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Nodule Composition

Nodules are primarily composed of metals like manganese, iron, copper, cobalt, nickel and other metals.

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Nodule Distribution

Nodules are especially abundant in the Pacific Ocean.

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Deep Sea Mining

The extraction of mineral resources from the ocean floor, typically at depths greater than 200 meters.

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Polymetallic Nodules

Rounded, potato-shaped rock formations found on the deep ocean floor, rich in minerals like manganese, copper, and nickel.

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International Seabed Authority (ISA)

An intergovernmental organization responsible for regulating activities in the international seabed area, including deep sea mining.

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Epifauna

Animals that live on the surface of the seabed or other marine objects, such as rocks or nodules.

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Anoxic Conditions

Environments lacking oxygen, such as the deep ocean floor where organic matter can be preserved.

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Organic Shale

A type of rock formed from compressed organic matter, like dead plankton, that can be transformed into oil and gas over millions of years.

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Oil and Gas Traps

Geological formations that prevent oil and gas from escaping to the surface, often formed by anticlines or unconformities.

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Sediment Sampling

The process of collecting samples of seabed sediments, often used by scientists to study marine environments, geology, and biological processes.

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Hydrogenetic nodule formation

Nodule formation where metals precipitate from oxygen-rich seawater, attaching to a central nucleus.

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Diagenetic nodule formation

Nodule formation where metals precipitate from low-oxygen pore water within sediments.

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Nucleus of a nodule

The central core or starting point for a nodule's development.

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Patchy distribution of nodules

Nodules are not found evenly across the ocean floor, but rather in scattered areas.

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Growth rate of nodules

Nodules grow very slowly, averaging around 10-20 mm per million years.

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Economic potential of nodules

Polymetallic nodules are a potential source of valuable metals, but their extraction is debated.

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Clarion Clipperton Fracture Zone

A region in the northeast equatorial Pacific considered a prime location for commercial extraction of polymetallic nodules.

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Study Notes

Chapter 1: The Physical Structure of Oceans

  • This chapter describes the major physical features and zones of the ocean, essential for understanding marine communities and organisms.
  • Figure 1.1 displays major oceans and seas. Table 1.1 provides depth and area statistics.
  • The average depth of the ocean is roughly 3,700 meters, with the deepest parts exceeding 10,000 meters.
  • Marine organisms are distributed unevenly but exist in the vast three-dimensional environment, even in the deepest parts.

1.1 Physical Features and Topography

  • A complete map of the ocean floor, showcasing features like plains, mountain chains, trenches, and shelves, is not yet fully available.
  • The GEBCO World Map (http://www.gebco.net) displays detailed depth contours and named features.
  • Major topographical features were mapped using soundings in the past and sonar in the 20th century. Figure 1.2 illustrates the location of major topographical features.

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Description

This quiz covers the major physical features and zones of the oceans as described in Chapter 1. You'll learn about ocean depth, marine topography, and the distribution of marine organisms. Understanding these concepts is essential for grasping the dynamics of marine ecosystems.

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