GPH 301 Lecture Notes

Flashcards about Geodynamics, Plate Tectonics, Continental Drift, Volcanicity, Earthquakes, and Earth's Interior, created from lecture notes.

Geodynamics

A subfield of geophysics concerned with the forces and processes within the Earth.

Purpose of Geodynamics

Helps us understand mantle convection, plate tectonics, seafloor spreading, mountain formation, and volcanicity.

What does Geodynamics help to understand?

Origin, causes, and effects of forces and motions within the Earth's interior, resulting in earthquakes and faulting.

Geodynamic studies use data from

Field observations, geodesy, radiometric dating, petrology, borehole drilling, and remote sensing.

Plate Tectonics

The outer rigid layer of the Earth (lithosphere), about 100km thick, divided into several plates that glide over the asthenosphere.

Primary and Secondary Plates

Large continental and medium-sized plates that make up the lithosphere.

How fast do plates move relative to each other?

About 5 to 10 cm (2 to 4 inches) per year.

What are the seven major plates?

African, Antarctic, Eurasian, North American, South American, Pacific, and Indo-Australian plates.

Convergent Boundaries

Occur when two or more plates move towards each other, resulting in subduction zones.

When does subduction occur?

When one of the plates is composed of oceanic crust, the denser plate is subducted below the less dense plate.

What forms when oceanic crust meets oceanic crust?

Island arcs and trenches, often accompanied by submarine volcanoes.

What is the result when oceanic crust meets continental crust?

Mountain range formation, e.g., the Andes.

What forms when continental crust meets continental crust?

Mountain formation, e.g., the Himalayas.

Divergent Boundaries

Boundaries where two plates move apart, filled with new crustal materials from molten magma; can eventually become ocean basins.

What forms Divergent boundaries within continents?

Produces rifts and rift valleys.

What are divergent boundaries under the sea called?

Often called mid-oceanic ridges.

Transform Boundaries

Boundaries where plates slide past each other; stress builds up and releases, causing earthquakes.

Continental Drift

The large-scale lateral movements of continents relative to one another and the ocean basins.

Alfred Wegener

German meteorologist who proposed the theory of continental drift in 1912.

What did Wegener propose?

A large supercontinent (Pangaea) throughout most of geologic time, which fragmented in the Triassic period.

What evidence did Wegener use to support his theory?

Geologic structure, paleontological evidence, and distribution of glacial deposits.

What explanation did Arthur Holmes come up with for why Continents move?

Heat trapped in the Earth caused convection currents.

What two premodial Continents were suggested by Alexander L. Du Toit?

Laurasia (in the North) and Gondwana (in the South).

What did Gondwana consist of?

South America, Africa, Madagascar, India, Australia, and Antarctica.

Volcanicity

All the processes associated with the movement of magma from the subsurface to the surface.

What determines the nature of a volcanic eruption?

The chemical composition of the magma, its temperature, and the amount of dissolved gasses within it.

Where do volcanic eruptions most often occur?

Occurs at tectonic plate boundaries, especially subduction zones.

What are the four categories of volcanic activity?

Exhalative, effusive, explosive, and subaqueous.

Exhalative Activity

Involves the discharge of material in gaseous form.

Effusive Activity

Refers to the outpouring of molten rock (lava) from a vent.

Explosive Activity

When solid materials are fragmented and ejected through vents.

Subaqueous Volcanism

Volcanism that occurs below the water surface, producing pillow lava.

What are the positive effects of volcanicity on the soil?

Volcanic ash and dust increase soil fertility.

Which countries produce geothermal power?

USA, Russia, Japan, Mexico, and New Zealand.

What are the main regions of volcanic activity?

Pacific Ocean region, Alpine-Himalayan region, and Atlantic and Indian Oceans.

Where does volcanic activity most often occur?

Converging plate margins and mid-oceanic ridges.

What happens when The strength of the rocks beneath the surface is exceeded?

Faulting.

The Main cause of a Earth Quake

Sudden release of energy in the Earth's interior.

What are the three types of seismic waves?

P-waves, S-waves, and Surface waves.

P-waves

Longitudinal or compressional waves that can pass through any medium.

S-waves

Secondary, shear, or transverse waves with particle motion perpendicular to wave travel direction.

examples of Surface waves.

Love and Rayleigh waves.

Earthquake Magnitude

Measure of the size or amplitude of seismic waves generated by an earthquake.

Earthquake Intensity

Measure of how severe the ground shaking is at a given location.

Types of earthquakes based on causative factor

Natural, volcanic, tectonic, isostatic, and plutonic earthquakes.

Classification of earthquakes based on focus depth

Shallow, intermediate, and deep-focus earthquakes, based on depth.

Earthquake Epicenter

Point on the surface directly above the focus (hypocenter).

Earthquake Focus

Exact point in the Earth's interior where seismic energy is released.

What does the crust of the earth consist of?

Consists of variable thickness unconsolidated sedimentary and metamorphic basements.

What is the crust divided into?

Continental and oceanic crust.

Mantle

Extends from the Moho to the Gutenberg Discontinuity (between 30-2900km).

obanic Crust

An oceanic Crust theiner layer.

Examples from Training Sectonic date andhyani's SDAN_015902705

Radomes, Geothermal, Tellurid, MT.

Classification by physical properties

Lithosphere (rigid), asthenosphere (plastic), mesosphere (rigid), outer core (liquid), and inner core (rigid).

Mention The earths discontinuities

Conrad Discontinuity, Moho Discontinuity, Gutenberg Discontinuity, and Lehmann Discontinuity.

Composition of lithosphere

Solid rock made mostly of silicon, aluminum, and oxygen (continental crust contains granitic rocks, oceanic crust contains basaltic rocks).

Composition of Core

Hot, softened rock containing iron and magnesium.

The lithosphere and asthenosphere

Division of the Earth based on mechanical properties.

Why Liquid or Gas medium do not contain S-Grave

Shear strengths.

Isostasy

Describes the naturally occurring balance of masses within the Earth's crust that keeps the planet in gravitational equilibrium.

Isostatic Equilibrium

State of gravitational equilibrium between the Earth's crust (or lithosphere) and mantle.

Concept of Isostasy

Suggests that excess mass of materials above sea level is due to a mass deficit below sea level.

Airy’s Hypothesis

Assumes the Earth's crust has uniform density but variable thickness (mountains have roots that extend deeper below the surface).

Pratt Hypothesis

Noted that the Earth's crust has varying thickness below sea level, supporting an equal weight per unit area (lateral variation in rock density).