Tectonic Processes & Hazards - EQ1 - 1.1 Flashcards
How do we map the structure of the earth
- seismic waves
Why do we map the tsructure of the earth using seismic waves
- it is 6,500km to the centre of the core
- the core’s heat is expected to be 6,000 degrees celcius
What is the composition of states of matter in the asthenosphere
- 90% solid & 10% liquid
What is the asthenosphere
- it is the upper layer of the earth’s mantle below the lithosphere
- the extreme pressure & heat in this layer cause the rocks to flow like a liquid
- the rocks in the asthenosphere are not as dense as the ones in the lithosphere - allowing the movement of tectonic plates around on the Earth’s surface
What is the lithosphere broken up into
- 7 major & minor parts called tectonic plates
Tectonic plates move…
It is this movement that creates…
relative to eachother over the asthenosphere
earthquakes & volcanic erruptions
Tectonic plates are very….. that vary greatly in…& move…
large slabs of solid rock that vary greatly in size & move slowly (about 2-15 cm a year)
What is the limitation to our understanding of tectonic plates
- plate boundaries are not clearly defined, in reality we are still working at where they are exactly
- the situation is complicated by the existence of faults
What are tectonic faults
- multiple cracks which spread out from boundaries
Where are the majority of earthquakes distributed
- the majority of earthquakes (about 95%) occur close to or at a plate boundary
- many occur around the ‘Ring of Fire’ surrounding the pacfic ocean
The most powerful earthquakes are usually associated with ….. or……. plate boundaries
- convergent or divergent
Where are volcanoes found
- most active volcanoes occur at or near to plate boundaries
- about 75% occur aorund the ‘Ring of Fire’ surrounding the Pacific Ocean
- most occur at either convergent or divergent plate boundaries, or at hotspots
What is the percentage distribution of tsunamis
- over 70% of tsunamis occur around the Pacific Ocean
- 15% Mediteranean Sea
- 9% Carribbean Sea & Atlantic Ocean
- 6% Indian Ocean
Where are most tsunamis found
Since they are caused by tectonic activity, they mostly occur at convergent boundaries
Where 2 tectonic plates meet, they form a ………. - each creating ……
- plate boundary
- distinct landforms & processes
It is at ……. ……. where most tectonic activity occurs
plate boundaries
What are plate margins
- the area adjacent to plate boundaries
- they include areas either sude of the boundary that may be affected by the movement
What are the 5 different plate boundary types
- divergent
- convergent
- transform
- collision
- complex
What are the 3 categories for covergent boundaries
- oceanic & continental
- oceanic & oceanic
- continental & continental
What are the categories for divergent & conservative boundaries
- oceanic & oceanic
- continental & continental
What are divergent plate boundaries
- constructive
- plates move apart (usually oceanic)
Where are divergent boundaries most often found
- ocean ridges
What normally occurs along divergent plate boundaries
- large numbers of shallow focus & generally low magnitude earth quake events
Give examples of where diveregent plate boundaries occur
- between Nazca & Pacific Plates