T1.1.2: Plate Tectonic Theory, (Continental Drift) Earthquake Wave Types Flashcards
Convection Currents definition and why they occur
Convection currents: describes the process of heat radiating out of the inner core resulting in circulation in the upper and lower mantle of the magma.
- Occurs from radioactive decay in the core resulting in heat being released
- Heat rises out into the mantle and then cools and circulates back down
Structure of the inside of the earth in order (centre to surface)
I - Inner Core
O - Outer core
M - Mesosphere (lower mantle)
A - Asthenosphere (upper mantle)
L - Lithosphere
Lithosphere features
- Temperature: approx (400oC)
- Density: least dense
- Composition: Granite (continental) and basalt (oceanic)
- State: Solid
- EQ: all pass through
Mantle features
Depth: 700km - 2890km deep
Temperature: 870oC (second coolest)
Density: second least dense
Composition: Periodite
State: Liquid and Solid
EQ: waves pass through at different rates
Outer Core characteristics
Depth: 2890 - 5150km deep
Temperature: 4400 - 611oC (third coolest)
Density: second least dense
Composition: mainly Iron
State: Liquid (generates magnetic field)
EQ: Only P-waves
Inner Core features
Depth: 5150 to centre deep
Temperature: 7000oC (radiative decay)
Density: Most dense
Composition: Mainly iron
State: Solid (radiates heat)
EQ: P-waves only
Plate tectonic theory definiton
- The hypothesis that the earth’ lithosphere consists of tectonic plates that experience continental drift resulting in changes to the earth’s surface and tectonic hazards
What is Pangaea?
- Refers to the initial supercontinent which is evidence for plate tectonic theory
Geological evidence for plate teconic theory
- The current continents visually appear to fit into other continents (East of South America looks to fit into West Africa)
- Glacial deposits found in South America, India and Antarctica (if made at the same time how are they in different locations
- Rock types: found in different regions around the globe (Scotland and Canada)
What are the processes of how tectonic plates move and define them?
- Ridge push
- Slab pull
- Sea floor spreading
- Paleomagnetism
Ridge push definiton and process
- Theory that convection currents cause hot magma and material to rise
- Hits the underneath of the crust and then diverges outward in different directions as magma then travels along and then down
- Pushes the crust in the same direction as the magma but in two opposite direction
- Mid-ocean ridges are elevated so here, gravity pulls the surrounding rock down and away form the ridge
Features of Ridge Push formation
Constructive plate boundary
Mid-ocean Risges: these are elevated series of underwater volcanoes or raised lithosphere where the magma has pushed the land upward.
Rift valley: the area between both ridges where magma rises and cools to form new crust
Slab pull definition and process
- Old dense slab of tectonic plate collides with another plate and is then subducted below it.
- Gravity pulls on the rest of this plate causing the whole plate to sink.
- Old Subducted slab is then melted providing new debris and magma
Slab pull features and formations
Destructive plate boundary
- Subduction zone: location where one plate is pulled into another
- Deep ocean trench: deep area in the ocean floor between where subduction occurs
What is sea floor spreading?
- Refers to the process of new young rock forming at a rift valley at a mid-ocean ridge
- As they form, over time, they are pushed apart by ridge push causing them to be distributed in different directions.
- Convection current moving these bands of rock causes sea floor spreading where young rock is near the ocean ridge and old rock is far from it near subduction zones
What is paleomagnetism and how does it work
- The earth’s magnetic poles attract certain rocks and metals towards them
- They influence the geology of rocks where the magnetic north causes an attractive force
- Results in newly formed rock to cool with its domains facing towards the north and preserving its direction of magnetic field.
- However, magnetic fields flip over time causing some rocks to then form preserving the opposite direction.
- Results in *alternating bands of rock** with positive and negative anomalies which can give an indicator of the age of the rock
Positive anomaly definiton
- Also known as Normal polarity
- Positive anomaly: Rocks cool with its minerals’ domains facing —> magnetic north.
Negative anomaly definiton
- Known as reverse polarity
- Rocks cool with their minerals’ domains preserving direction —> magnetic south
Primary wave definition and their characteristics
- seismic wave that vibrates rock particles in the direction it travels. Arrives 1st
F - Fastest wave
A- All: travels through all solids/liquids
C - Compresses (transverse)
E - Expands (transverse)
S - Short Wavelength
Secondary wave definition and its characteristics
A wave that moves in a perpendicular manner to the direction of wave travel. Causes the ground to move up and down. Arrives 2nd
L - longitudinal wave
L - liquid: travels only through liquids
P - perpendicular
- Second fastest, second shortest wavelength
Love wave definition and its characteristics
A type of wave which travels horizontally at the surface but perpendicular to the direction of travel. Arrives last
D - Destructive (most)
A - Amplitude is highest
S - Surface
S - Slowest
H - Horizontal motion
