The Origin and Evolution of the Marine Environment (MSCI*112)

Flashcards cover key concepts from Earth's internal structure (crust, mantle, core), discontinuities (Moho, Gutenberg), seismic waves (P/S, Rayleigh/Love, shadow zones), geodynamics (geodynamo, isostasy), and take-home facts about thicknesses, temperatures, and processes like isostatic adjustment.

Describe the density of the Earth's crust relative to other layers.

The crust is the least dense and outermost solid layer of the Earth.

What is the significant seismic boundary separating the Earth's crust from the underlying mantle, first identified by Andrija Mohorovičić?

The Moho discontinuity (or Mohorovičić discontinuity). It marks a distinct increase in seismic wave velocities.

What is the major internal boundary of the Earth located between the mantle and the outer core, also known as the Gutenberg discontinuity?

The Core–Mantle Boundary. It is characterized by a significant change in material properties and a sharp decrease in seismic wave velocities.

What is the primary rock type that constitutes the Earth's mantle, characterized by its richness in iron (Fe) and magnesium (Mg) and lower content of aluminum (Al) and silicon (Si)?

Peridotite.

Describe the physical state and properties of the asthenosphere.

The asthenosphere is partially molten and exhibits ductile, 'jello-like' behavior, allowing for slow convection currents.

Describe the physical state of the Earth's outer core.

The outer core is entirely liquid, composed mainly of iron and nickel.

Describe the physical state of the Earth's inner core.

The inner core is in a solid state, despite extremely high temperatures, due to immense pressure.

What is the process within the Earth's liquid outer core responsible for generating the planet's magnetic field?

The geodynamo, driven by the convection of molten iron.

Describe the frequency of Earth's magnetic field reversals.

Earth's magnetic field reversals occur irregularly over geological timescales, ranging from relatively frequent to much longer intervals.

Describe the nature of P waves (Primary waves) in seismology.

P waves are compressional (longitudinal) seismic waves, meaning they propagate by pushing and pulling material in the same direction as the wave's movement. They are the fastest seismic waves and can travel through solids, liquids, and gases.

Describe the nature of S waves (Secondary waves) in seismology.

S waves are shear (transverse) seismic waves, meaning they oscillate material perpendicular to the direction of wave propagation. They are slower than P waves and can only travel through solid materials.

Describe the primary characteristics of Rayleigh waves and Love waves, which are types of surface seismic waves.

Rayleigh waves cause particles to move in an elliptical motion, combining both compressional and shear components. Love waves involve horizontal shearing motion, perpendicular to the direction of wave propagation and parallel to the Earth's surface.

What type of waves do seismographs detect and record?

Seismographs record seismic waves, which are elastic waves produced by earthquakes or other Earth disturbances that travel through the Earth's interior and along its surface.

Why are S waves unable to propagate through the Earth's outer core?

S waves cannot pass through the Earth's outer core because it is in a liquid state. Shear waves require a solid medium to transmit their oscillatory motion.

State Archimedes' Principle in the context of floating objects.

Archimedes’ Principle states that the buoyant force on a floating object is equal to the weight of the fluid that the object displaces.

Differentiate between the Airy and Pratt models of isostasy in explaining Earth's topography.

The Airy model explains topography through variations in crustal thickness, suggesting mountains have deep crustal 'roots'. The Pratt model explains topography through lateral changes in crustal density, where higher elevations correspond to less dense crust.

Define isostasy in terms of Earth's crustal behavior.

Isostasy is the state of gravitational equilibrium between Earth's lithosphere and asthenosphere, where the crust adjusts its vertical position in response to changes in mass (like ice sheets or erosion) to maintain buoyancy and restore equilibrium.

How does the removal of a large ice sheet affect the Earth's crust?

The melting and removal of significant ice sheets lead to crustal rebound (or post-glacial uplift), as the underlying lithosphere slowly rises to restore isostatic equilibrium after the immense weight of the ice has been removed.

Compare the thickness of the crust beneath the Himalayan mountain range to that beneath the Appalachian mountains.

The Himalaya crust is significantly thicker than the Appalachian crust, reflecting its active ongoing collisional tectonics compared to the older, eroded Appalachians.

What constitutes the lithosphere?

The lithosphere is the rigid outermost layer of the Earth, comprising the entire crust and the uppermost, solid part of the upper mantle.

Where is the asthenosphere located in relation to the mantle?

The asthenosphere is located beneath the lithosphere, forming the ductile, flowing portion of the upper mantle.