Marine Geology Overview

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Questions and Answers

Which statement accurately describes the oceanic crust?

It is thick and composed mainly of granite.

It floats higher on the mantle than continental crust.

It is less dense than the continental crust.

It is thinner than continental crust and primarily composed of basalt. (correct)

What evidence did Alfred Wegener use to support his theory of a supercontinent?

The consistent layer of sediment found in the ocean floors.

The symmetrical banding of magnetic anomalies.

Formation of mid-ocean ridges.

The presence of identical minerals and fossils across continents. (correct)

Which type of plate boundary involves tectonic plates moving toward each other?

Static boundary

Convergent boundary (correct)

Divergent boundary

Transform boundary

What does the presence of isotopes like O-18 and O-16 in microscopic organism shells indicate?

The temperature of ancient seawater. Signup and view all the answers

What event marks the period known as the Cambrian Explosion?

A rapid radiation of life forms. Signup and view all the answers

In terms of wave behavior, what happens when waves propagate in shallow water?

Their speed decreases as the depth decreases. Signup and view all the answers

Which factors influence the potential height of wind-generated waves?

Wind speed, duration, and fetch. Signup and view all the answers

How can we categorize tides based on their daily patterns?

Diurnal, semidiurnal, and mixed elements. Signup and view all the answers

What occurs during spring tides?

Tides are exaggerated Signup and view all the answers

What characterizes the Mesozoic marine revolution?

An enhancement in predator-prey interactions in marine ecosystems. Signup and view all the answers

What major geological feature provides evidence for plate tectonics?

Mid-ocean ridges. Signup and view all the answers

What effect does the Coriolis force have in the northern hemisphere?

It causes water to move to the right Signup and view all the answers

What is a primary characteristic of coastal upwelling?

Warm water is displaced from the coast Signup and view all the answers

What does El Niño typically influence in the eastern Pacific?

Significant warming of surface waters Signup and view all the answers

What drives the Walker Circulation under normal conditions?

Trade winds blowing from east to west Signup and view all the answers

What is a characteristic of neap tides?

They result in a very small tidal range Signup and view all the answers

What is the role of the thermocline in ocean thermodynamics?

Acts as a barrier to temperature changes Signup and view all the answers

What motivates the formation of subtropical gyres?

Trade winds pushing water into a high-pressure area Signup and view all the answers

Which of the following describes the Antarctic Bottom Water (AABW)?

A signature based on temperature and salinity Signup and view all the answers

What happens to ocean temperatures during summer months?

Construction of a thermocline occurs Signup and view all the answers

Where does cold dense water primarily sink to form abyssal water?

In the North Atlantic Signup and view all the answers

What impact does El Niño have on coral reefs?

Creates a short-term increase in water temperature Signup and view all the answers

What is one result of the Southern Oscillation?

Shift in sea level pressure between Tahiti and Darwin Signup and view all the answers

Which phenomenon results from equatorial divergence?

Upwelling of cool, nutrient-rich waters Signup and view all the answers

Study Notes

Marine Geology

Earth’s outer crust comprises oceanic and continental crust.
Oceanic Crust: Thin, dense, basaltic; floats lower on the mantle.
Continental Crust: Thick, less dense, composed of granite.
Upper Mantle: Solid but plastic; can flow over long timescales due to high temperatures.
Core Composition: Molten outer core and solid inner core.

Paleobiogeography

Alfred Wegener proposed a supercontinent based on aligned minerals and fossils.
Mid-ocean ridges show magnetic anomalies and symmetric banding, indicating tectonic activity.
Newest rocks form at mid-ocean ridges; old rocks are recycled at deep-sea trenches.
Plate movement is driven by convection and slab pull.

Plate Tectonics

Oceanic and continental crusts interact via tectonic plates.
Divergent Boundaries: Plates move away from each other.
Convergent Boundaries: Plates move toward each other.
Transform Boundaries: Plates slide past each other at an angle.

Sediment and Marine Creatures

Historical study of sediments reveals past productivity and temperature through shell analysis.
Isotopic ratios (e.g., O-18/O-16) indicate historical ocean temperatures.

Mass Extinctions

Five mass extinctions have occurred in Earth's history; the planet is currently in the sixth.

Types of Fossils

Fossils are categorized into body, trace, and chemical fossils.

History of the Ocean

Mass extinctions occur approximately every billion years, excluding asteroid impacts.
Earth’s first billion years led to the emergence of photosynthesis; subsequent billions saw multicellular life evolve.
The Cambrian Explosion, around 550 million years ago, marked the emergence of diverse animal forms.

Cambrian Explosion

Associated with conditions such as a snowball Earth, leading to a gene revolution and rapid diversification of life.

Fauna Evolution

Evolution has led to distinct faunal communities: evolutionary, Cambrian, Paleozoic, and current fauna.

Mesozoic Marine Revolution

A significant change in ocean ecosystems promoting larger predator-prey dynamics and increased primary production.

Ocean Waves

Waves can be constructive (increasing height) or destructive (canceling each other out).
Wave propagation entails energy transmission, not mass movement.
Factors influencing wave speed include water depth and shoreline interaction.
Tsunamis are generated by seafloor movement and can travel at high speeds (550 mph).

Tides

Tides result from gravitational and centrifugal forces, creating bulges of water.
Types of tides include diurnal, semidiurnal, and mixed semidiurnal.
Spring tides are exaggerated, while neap tides are attenuated.
Rotary tides create amphidromic points with variations in tidal height.

Atmosphere and Ocean Interaction

Increased water vapor reduces sea-level pressure; moist air rises, leading to precipitation.
Atmospheric convection drives weather patterns and the Coriolis effect influences trade winds.

Ocean Temperature

The thermocline forms seasonally, acting as a barrier due to temperature stratification.
Seasonal heating alters surface temperature and impacts mixing depth.

Ekman Transport

Wind movements cause water to shift: right in the northern hemisphere and left in the southern hemisphere.
Geostrophic currents flow along pressure gradients.

Gyres and Upwelling

Subtropical gyres form as trade winds push water into high-pressure centers, causing rotation.
Coastal upwelling brings cold water to the surface, whereas downwelling occurs when water is pushed down.

Water Circulation and Signature

North Atlantic Deep Water (NADW) and Antarctic Intermediate Water (AAIW) have distinctive temperature-salinity signatures indicating their origins.
Cold water sinks in the North Atlantic; North Pacific water remains buoyant due to lower salinity.

Coriolis Effect

In the Northern Hemisphere, the Coriolis effect deflects currents to the right, while in the Southern Hemisphere, it deflects to the left.

Conveyor Belt Circulation

Surface and deep ocean currents form a heat exchange system, moving heat from the equator to higher latitudes.

El Niño and Southern Oscillation

El Niño is associated with seasonal warming and occurs every 3-7 years.
The Southern Oscillation refers to atmospheric pressure variations between Darwin and Tahiti.

Walker Circulation

Normal conditions feature trade winds blowing east to west, while El Niño conditions reverse this pattern, impacting global weather.

Global Temperature Anomalies

El Niño events create significant short-term temperature increases, affecting ecosystems like coral reefs.

Impacts of El Niño

Direct impacts include altered rainfall patterns and temperature changes in ocean depth affecting marine productivity.
Indirect impacts involve shifts in jet stream positioning, which can influence weather patterns globally.

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Description

Explore the fundamentals of marine geology, focusing on the structure of Earth's crust and mantle. This quiz covers the characteristics of oceanic and continental crust, as well as the properties of the upper mantle and Earth's core. Test your knowledge of these geological layers!