Tectonics facts Flashcards
(122 cards)
example of a divergent plate boundary w/ oceanic crust
- mid atlantic ridge
2. 3km long
what % of earthquakes occur on pacific ring of fire
70%
name some characteristics of continental crust
30-50km thick
-layer of granite, sedimentary and metamorphic rocks floating on mantle
how many volcanos are there in the world and how many erupt each year
500
-50 yearly
name some characteristics of oceanic crust
6-8km thick
- thinner and composed of several layers
- top layer composed of basalt
how much do plates move a year
5-15 cm
what is james huttons theory of the earth
- 1785
- realised erosion, deposition and uplift were connected and these processes operate continuously
- driven by earths internal heat
why is nepal prone to earthquakes and how big was the 2015 Earthquake
sits on continental meets contental plate boundary between eurasian and india plates and is a conservative boundary where two continental plates collide
-2015 7.8 mag earthquake
example of fold mountains
himalayas
name 3 types of plate boundary
convergent-destructive margins
divergent- constructive margins
conservative- transform margins
example of rift valley
east african rift valley, divergent plate boundary with continental crust
what % of earthquakes are along plate boundaries
95%
examples of secondary effects of an earthquake
- landslides or avalanches
- tsunamis
- liquefaction
what was the main reason for damage in lloma prieta
rock type- softer rock amplifies the effects of the earthquake
- the marina district was built on soft sandy soil which amplified ground shaking and liquified causing buildings to collapse
- the area of the freeway built on bedrock did not collapse
give example of transform fault and how big was the last earthquake here
san andreas
1906- 8.3
what are pyroclastic flows
how fast flow?
how hot?
- mixture of hot dense rock, lava, ash and gases ejected
- destroys everything in paths
- much faster than lava flows as they are 100km/h
- 700 degrees
what kind of plate boundary was the loma prieta earthquake on
conservative
when was the loma prieta earthquake
1989
what are lava flows
how hot??
- streams of lava erupt onto earths surface, destroy everything in path but not generally life threatening as its slow moving
- 1170 degrees and take years to cool
what are lahars and how fast do they flow
vary in size and speed can we 100m’s wide and travel 10m/s so too fast to outrun
A lahar is a mudflow composed mainly of volcanic debris and water. They are formed when rainwater washes away the volcanic ash on a volcano slope. Sometimes caused lahars when crater lakes leak. Lahars are among the biggest risks of a volcanic eruption
over last 300 years how many have died due to volcanic hazards
260,000
how many evacuated in iceland eruption
700
how much did airlines lose in iceland eruption
$1.7 billion
how high did the plume of very fine volcanic ash of icelands volcano go
33,000 ft
which spread over west europe