Dynamic Earth Flashcards
Waves - general description
They carry energy and travel through a medium from one location to another. The medium does not travel with the wave.
Transverse waves (description)
Particles in medium vibrate in direction perpendicular to direction wave is moving. (E.g. light, water, electromagnetic waves)
Longitude waves (compressional) - description
Particles in medium vibrate in direction parallel to direction wave is moving (e.g. sound waves)
Primary (P) Waves
- Fastest seismic wave
- Push and pull rock in same direction that wave moves
- Can travel through solids, liquids and gases
- Compressional
Secondary (S) Waves
- Second fastest seismic wave
- Shifts rock at angle perpendicular angle relative to wave movement
- Only travels through solids
Love (L) waves
- Slowest seismic wave
- Travels along Earth’s surface (outermost layer)
- Most destructive
- Rolling, shaking motion
Features of transverse waves
Crest/peak: Highest position
Trough: Lowest position
Amplitude (in m): max height particle travels from original position
Wavelength (in m): distance between 2 crests or troughs on neighbouring waves/distance one particle travels to return to its original position
Frequency (in hertz/hz): number of complete wavelengths passing a point in one second
Features of longitudinal waves
Wavelength: distance between middle of one area of compression to the next
Amplitude: density of lines in one area of compression
Rarefaction: Area between compressions
Speed formula for waves
Speed (in m/s): distance wave travels per second
Speed = frequency x wavelength
(E.g. 1 x 1 = 1m/s)
Structure of the earth
Crust:
- Outer shell of rock
- Thinnest layer of Earth
- Divided into thicker continental crust and younger, denser oceanic crust
- Solid
Mantle:
- Mixture of solid and liquid (solid in upper mantle)
- Thickest layer
Outer core:
- Liquid
- Composed of iron and nickel
- Extremely hot
Inner core:
- Innermost layer of earth
- Composed of iron and nickel
- Extremely dense
- Solid
Earths spheres + descriptions
Lithosphere: Solid, outer part of earth (upper mantle and crust)
Asthenosphere: Denser, weaker layer beneath lithosphere (part of upper mantle)
Atmosphere: gases (the air)
Hydrosphere: All water (includes cryosphere)
Biosphere: all living things
Underlying convection of heat energy in terms of particle model
- Heat energy carried by movement of particles of matter
- Occurs when particles with thermal energy in liquid or gas move, taking place of particles with less thermal energy
- Difference in temperature and density causes hotter, less dense particles to rise, and cold, dense particles to sink
Convection currents
Process that involves movement of energy from one place to another (heat transfer)
- Unequal heat distribution in mantle = convection currents = movement of tectonic plates
- Magma rises under a divergent boundary, spreads out, moves plates away from each other, then cools and sinks to be reheated again
Gravitational forces
- Lithospheric plates pushed apart at hot spreading centres
- Cold lithospheric plates sink into mantle, pulling rest of plate down with it (slab pull caused by gravity)
- When molten magma rises to Earth’s surface between divergent boundary, it will thicken and cool, creating a new crust.
- It will be pushed downhill as new magma emerges (ridge push)
Circum Pacific Belt/Ring of Fire
- Experiences frequent earthquakes and active volcanoes
- Belt exists along boundaries of tectonic plates where oceanic plates sink underneath continental plates, leading to formation of volcanoes and earthquakes
