Earth's Interior, Plate Tectonics, Ocean Sound and Light, Water Properties

Flashcards covering seismic wave propagation, Earth's interior structure, plate tectonics evidence, ocean acoustics (SOFAR channel), light penetration, and the special physical properties of water including density and its influence on ocean dynamics.

What are the primary causes of seismic waves?

Earthquakes, volcanic eruptions, and human-made explosions.

What factors influence the speed of seismic waves?

Chemistry/density and physical state (solid, partially molten, or molten).

What are the three major types of seismic waves?

P-waves (compressional), S-waves (shear), and Surface waves.

What do shadow zones in seismic wave propagation indicate?

Information about internal boundaries and the state of layers, such as liquid versus solid layers, due to refraction when wave speed changes with depth.

In a typical seismogram, which type of wave arrives first, and what follows it?

P-waves arrive first, followed by S-waves, then surface waves.

How is Earth's interior layered chemically?

By crust, mantle, and core, based on compositional differences.

How is Earth's interior layered physically, and what are these layers?

By rigidity/deformability into the lithosphere (crust + rigid mantle) and the asthenosphere (deformable mantle).

What is the concept of isostasy?

The principle that rigid rocks float in a more ductile or less rigid underlying layer, such as continents on the mantle.

What do seismic velocities tell us about the state of the inner and outer core?

The inner core is solid iron, and the outer core is molten iron.

Which type of seismic wave travels through all Earth layers (solid and liquid), and which does not propagate through liquids?

P-waves travel through all layers, while S-waves do not propagate through liquids.

How many seismic stations are needed at a minimum to locate the epicenter of an earthquake using triangulation?

At least three stations are required.

What is the primary evidence cited by Alfred Wegener for his Continental Drift Hypothesis?

Jigsaw puzzle fit of continents, fossil evidence, matching rock types/structures across oceans, and paleoclimatic evidence (e.g., glacial deposits in tropical regions).

Why was Wegener's Continental Drift Hypothesis initially met with resistance?

He could not provide a plausible mechanism to explain how the continents moved.

What bathymetric features were revealed by maps, such as those by Bruce Heezen and Marie Tharp, that support plate tectonics?

Consistent features like mid-ocean ridges (often with a rift valley) and deep trenches.

How do earthquake epicenter locations support the theory of plate tectonics?

Earthquake epicenters clearly delineate plate boundaries, and in subduction zones, earthquake depth progressively increases.

Where is heat flux from Earth's interior predicted to be highest according to plate tectonics, and why?

It is highest at mid-ocean ridges because hot mantle material rises there.

How does sediment thickness and age on the ocean floor support seafloor spreading?

Sediments are thicker and older as one moves further away from mid-ocean ridges, where new oceanic crust is formed.

What evidence from magnetic field reversals is found on the seafloor to support seafloor spreading?

A symmetric pattern of normal and reversed magnetic polarity stripes on either side of mid-ocean ridge crests.

What did the concept of 'apparent polar wandering' paths from different continents demonstrate when they were aligned?

It provided strong evidence that continents have drifted over time, as these paths only align if the continents are brought back to their original positions consistent with plate tectonic reconstructions.

What special channels do whales utilize for long-range communication in the ocean?

SOFAR (Sound Fixing and Ranging) channels.

What two physical properties primarily influence the speed of sound in water?

Temperature and pressure (depth).

How does increasing temperature generally affect the speed of sound in water?

Sound travels faster because both the bulk modulus increases and density decreases.

How does increasing pressure (depth) generally affect the speed of sound in water?

Sound travels faster because the bulk modulus increases proportionally more than density, making the water 'stiffer'.

At what intermediate depth does the slowest sound speed typically occur in the ocean, forming the core of the SOFAR channel?

Around 1000 meters.

Why does the SOFAR channel allow sound to travel immense distances?

Sound waves refract (bend) back into the slow-speed layer, effectively trapping the sound within the channel with minimal energy loss.

What is primarily absorbed first, and what color penetrates deepest in the ocean?

Red light is absorbed most rapidly, while blue light penetrates deepest.

What feature of water molecules is responsible for many of water's unique properties, such as high heat capacity and surface tension?

Hydrogen bonds, which are intermolecular attractions due to water's polarity.

Why does water have a high heat capacity?

A significant amount of energy is required to break the hydrogen bonds between water molecules before their kinetic energy (and thus temperature) can increase.

At what temperature does freshwater reach its maximum density?

Approximately 4°C.

How does the density-temperature relationship of seawater differ from freshwater?

For typical ocean salinity, seawater density monotonically increases as temperature decreases (it gets denser the colder it gets), without the 4°C anomaly found in freshwater.

What drives the 'Great Ocean Conveyor Belt' and global ocean circulation?

Density-driven processes, particularly in polar regions, where cold, dense waters sink and spread throughout the deep ocean.