End of Topic Test Flashcards
(32 cards)
What is an Earthquake
A violent shaking of the ground. Typically causing destruction as a result of movements within the earth’s crust or volcanic activity.
Focus
The origin of the earthquake
Epicentre
Point on the Earth’s surface directly above the earth’s epicentre
Fracture Zone
Fracture Zone is a point in the earth’s crust where there is cracks but no movement
Fault Sone
A crack in the earth’s crust along which there is movement
Surface wave
A wave that travels across the surface of the Earth as opposed to through it
Body wave
A wave that travel’s through the earth’s inner layers
P wave
A longitudinal wave which travels through the earths layers (body wave) and is the first wave to be recorded on the seismograph
S wave
A wave that moves perpendicular to its propagation. Transverse slower than the P wave. Surface wave
What is the Richter Scale?
Logarithmic scale, expressing the magnitude of an earthquake based on a seismograph oscillations. Logarithmic Scale means that everything is x 10.
Utilising Seismic Waves to locate Earthquakes
- Draw a vertical line across the time when P- waves are first detected and a vertical line where S waves are first detected
- Calculate the time lag ( 275-60= 215s)
3.Calculate distance of earthquake from recording station
(215/5) x 60= 2580km
Seismometer and how does it work?
Instrument that measures and records details of earthquakes. The Seismometer is bolted to the ground so the entire case moves, the one part of the seismometer that does not move, however, is the seismometer, which is a suspended mass hung by a wire. Movements of the magnet relative to the case generate small electric signals in the wire, which can be sent to a computer or recorded onto paper to create a seismogram.
Where do Earthquakes most commonly occur?
At plate boundaries
Earthquakes are deeper further away from plate boundaries
Earthquakes that are not at plate boundaries occur at subducting slabs. The deepest earthquakes occur within the core of subducting slabs - oceanic plates that descend into the Earth’s mantle.
Continental Drift theory and Plate Tectonics
Earth’s crust is not a solid piece it is broken up like egg shells. The rock is broken up into tectonic plates that ride atop the magma, (hot molten rock) that makes up much of the interior of earth. The continents are on tectonic plates. Therefore, over millions of years, the continents drift into new configurations.
Ridge push
- hot mantle rises at mid oceanic ridge
- new thin surface is created thinner crush pushed upward causing incline
- greater distance from Mid Ocean Ridge greater thickness of crust
- thicker crust = greater mass
- pulling thinner new crust away from Mid Ocean Ridge
Mantle Drag
Mantle currents carry plates of lithosphere along on top like a conveyer belt.
THEORY NOT SUPPORTED BY EVIDENCE THOUGHT TO OCCUR IN MANTLE.
Slab Pull
- older denser basalt oceanic plate sink into hotter less dense mantle and pulls rest of attached plate.
- plate moves faster at subduction zone ( supports theory)
Subduction
Less dense continental crust subducts underneath more dense oceanic crust
What is Pangea
Over 225 million years ago there was thought to be one giant land mass - Pangea, that has since broken up into various plates that have slowly moved into new positions.
Gondwanaland
Remains of the supercontinent( Pangea) made up of South America, Africa, Antartica, India and Australia
Jigsaw Continents
This theory supports continental drift. It essentially means that the coastlines of the existing continents, when put together fit like a jigsaw, and also make the shape of Pangea when constructed as one large land mass
Tectonic Plate Theory
Plate tectonics is a scientific theory describing the large-scale motion of earth’s tectonic plates.
1st Evidence
Jigsaw Puzzle( explained in continent jigsaw slide)
