Earthquakes, seismic waves and plate tectonics Flashcards
What is the definition of “disaster”
A natural event which causes injury or damage to any living being
What is the definition of “natural”
An event not caused directly or indirectly by human actions
how many layers does the earth have?
6
What is the outermost layer of the earth?
The Crust
What comes after the outermost layer of the earth?
The mantle
How is the mantle structured?
Into an upper rigid mantle, a soft mantle and lower mantle (ordered from top to bottom)
Whats a synonym for the soft mantle?
Asthenosphere
What are some features of the asthenosphere?
It is hot, slippery and weak
What comes after the mantle?
The Outer and Inner core
What are some features of the outer core?
Liquid and molten, starting at ~3000km below surface
What are some features of the inner core?
Completely solid, starting at +5100km below surface, dense and thought to be origin of magnetic field (composed of iron and nickel
How does the temperature evolve the deeper one travels through the layers of the earth?
The temeprature increases by 3°C per 100m depth
Do the core layers possses the same thickness as the mantle layers?
No, the mantle layers are 2900km thick whilst the outer core is only 2200km thick and the inner core even less with only 1271 km of thickness
What types of seismic waves exist and what defines them?
P-Waves, S-Waves and Surface-Waves
P= primary, moves through solid and liquid layers, cannot be felt by humans
S= secondary, don’t move through liquid layers, can be felt by humans/cause damage
Surface = Cause destruction after P- and S-Waves
How is the strength of an earthquake measured and when is an earthquake considered dangerous?
Using the Richter-Scale, >6.5= dangerous
What theory did Alfred Wegener pioneer about the history of the geography of the earth?
The Continental Drift Theory, that all continents where once a part of a larger, contiguous landmass and drifted apart over time
What proof did Alfred Wegener as the foundation of his theory?
The existence of similar fossils on completely distinct and geographically isolated continents
How was the theory conclusively proven correct?
by the US scientist Harry Hess in 1962, who found mountains and ridges underwater
What is the cause of continental drift?
Plate tectonics
What are the different types of plate tectonics?
Convergent, divergent and subduction
What is the key characteristic of divergent plate tectonics?
That two plates begin to seperate (diverge) from each other, producing a new crust between (productive)
What is the key characteristic of convergent plate tectonics?
Two plates begin to come together (converge) and fold over each other (can create mountains like Himalayas)
What is the key characteristic of subduction?
One part of the crust moves underneath another area of crust (subduction), melting the lower crust and giving rise to magma bubbles that can be the source of volcanoes
How do volcanoes form?
By sitting atop a magma pipeline that feeds magma to the top from a magma plume and originates at the core-mantle boundary
