Physical Geography Hazardous Earth Flashcards
Average depth of continentalcrust
35km
Density of continental crust
2.6 kg/m^3
Depth of oceanic crust
10km
Density of oceanic crust
3kg/m^3
Depth of lithosphere
crust-100km
Characteristics of the lithosphere
Rigid
Depth of Asthenosphere
100-300km
Characteristics of asthenosphere
Plastic
Depth of mesosphere
300-2900km
Characteristics of mesosphere
Solid
Depth of core
2900-6400km
Inner core characteristics
Solid iron and nickel
Outer core characteristics
liquid
When did maps of seismic activity emerge
1960s
Evidence for continental drift and plate techtonics
Plate movement
geological evidence
biological evidence
paleomagnetism
the age of sea-floor rocks
Define plate movement
convection currents due to rising parts of the asthenosphere that reach lithosphere, dragging the techtonic plates.
Who originally proposed continental drift
Alfred Wegener 1912
Examples of geological evidence for plate techtonics
Fit of SA and africa
Glaciacion of India, Australia
Biological evidence for plate techtonics
Glossopteris fossil found in Antarctica, Australia, India
Mesosaurus in SA and Africa
Define paleomagnetism
Changes in earths polarity is recorded in minerals on the sea floor.
How does the age of the sea floor rocks present evidence for plate techtonics
oldest sediments found near continents, younger deposits found out in oceans.
Large scale trenches suggest that crust subduction into the asthenosphere
Define ridge push
Plate pushed by the weight of a mid-ocean ridge
Define slab pull
Plate pulled by the weight of its cold, dense subducting region.
Define convection currents
Plate dragged by a convection current in the mantle
What boundry occurs during divergent plate movement
Constructive boundry
What boundry occurs during convergent plate movement
destructive (oceanic to continental)
What boundry occurs during transform plate movement
conservative
What boundry occurs during convergent plate movement (continental - continental)
collision
What boundry occurs during convergent plate movement (oceanic - oceanic)
destructive (oceanic to oceanic)
What type of lava is in an explosive eruption
Acidic
What type of lava is in an effusive eruption
Basic
Properties of pyroclastic flow
Explosive eruption
Up to 500 degrees
Poisonous
Faster than 100mph
Properties of tephra
Explosive eruption
Tiny fragments of rock thrown by an eruption (often creates volcanic ash)
Properties of Poisonous gas
Explosive and effusive
Carbon monoxide, Carbon dioxide, sulfur dioxide
produces acid rain
Properties of a lahar
Explosive eruption (must have tephra)
Fast flow of mud and tephra produced by heavy rains after an eruption
local, up to 50kmph
Properties of a tsunami in an eruption (+speed)
Explosive eruption
wave speed up to 600kmph
Define Jokulhlaup
Explosive and effusive eruptions
sudden release of glacial melt water
Define volcanic winter
Effusive and explosive
Global scale, can cause food shortages.
Sulphur dioxide
What are techtonic plates made of
Crust and lithosphere
What is a volcano
A landform created by eruption of molten rock
Define volatile
Evapourates without energy (water)
Rock can now melt as volatiles have been added (destructive boundry)
Define decompression
No longer being pushed down by crust
Allows rock to melt and erupt (shield)
Plate boundry of basic lava
Constructive/ divergent
Type of melting/eruption for basic lava
decompression
Which layers melt to form basic lava
Mantle
Viscocity and silica content of basic lava
Not viscous, less silica
How are gasses vented in basic lava
Vented steadily
What types of rocks are produced by basic lava
Basalt
Temp of basic lava
Up to 1200
eruption type of basic lava
effusive
Volcano shape of basic lava
sheild, fissure
Plate boundry of acidic lava
destructive
Type of melting for acidic lava
Addition of volatiles during subduction
Which layers melt to form acidic lava
oceanic crust
Viscosity and silica content of acidic lava
Viscous, high silica
How are gasses vented in acidic lava
trapped until violent eruption
Type of rock produced by acidic lava
Andesitic
Temp of acidic lava
650 - 1000
eruption type of acidic lava
explosive
Volcano produced by acidic lava
composite / strato
What is VEI and what does it measure
Volcanic explosivity index
Magniude (how much material)
Intensity (how fast)
What is VEI and what does it measure
Volcanic explosivity index
Magniude (how much material)
Intensity (how fast)
What is the term for the limit where rock cracks
threshold
What happens when stress reaches threshold
plates jolt
Define focus
where the rock cracks underground
Define seismic waves
stress release causing jolts, vibrate through rocks on the surface
epicentre
point on surface above focus
What is the wadati-benioff zone
Zone of EQs next to destructive plate boundry
70 - 700km deep
What does the richter scale measure
magnitude (amount of energy released on a logarithmic scale)
What does the modified mercalli scale measure
Damage / intensity (qualitative descriptions of damage in 12 catagories)
What does the moment magnitude scale measure
Magnitude (how much ground shaking occurs)
Define P waves
Primary
Ground shakes laterally
moderate damage
fast
Define S waves
Secondary
Ground shakes vertically
slight damage
average speed
Define L waves
Surface
Ground shakes rolling
Severe damage
slow
Effects of liquefaction
Structures tilt and sink
Fine grain sands behave like water
Define pillow lava
Underwater divergent boundry
basaltic lava
Landforms created by divergent boundrys
In water - mid ocean ridge
On land - rift valley
Describe formation of rift valley
Rising mantle rock
Pushes crust into dome
Divergence (uplift) causes crust to fault and crack
Rock is weakened - dome subsides
Creates steep valley sides + flat floor
How do some volcanoes become calderas
Magma chamber empties and unsupported rock above collapses
crater and collapsed roof remain
Moment magnitude of Japan earthquake
9.0
Date of japan earthquake
2011
Height of tsunami japan 2011
40
How many people died japan 2011
16,000
GDP of Japan
39,000
Mitigation against the event japan 2011
sea wall
Mitigation against vunerability japan 2011
research + monitoring
building design
education
Mitigation against losses japan 2011
rescue workers (100,000 from armed forces)
slow recovery from fukushima
rehearsed plans
Moment magnitude of Haiti eq
7.0
date of haiti eq
2010
how far was epicentre from port au prince
25km
building faliures? haiti 2010
pancake collapse
how many people died haiti 2010
230,000
how many ppl made homeless haiti 2010
2.3 million
Mitigation against the even haiti 2010
none
Mitigation against vunerability haiti
new eq proof buildings
world bank waived dept for 5 years
Mitigation against losses haiti
3500 US troops
NGO for emergancy shelters, food + water
GDP per capita of Haiti
1,800
GDP of italy
36,000
economic impacts of mt etna eruption
tourism decrease
orange + vineyards destroyed
mitigation against the event etna
earth barriers
concrete blocks
mitigation against vunerability etna
volcano monitoring
promt evacuations
mitigation against losses etna
families can afford insurance
government compensation
well resourced public services
GDP of indonesia
4,000
how far did the pyroclastic flows reach marapi
15km
economic impacts of marapi
livestock killed
farms + crops destroyed
How many poeple died merapi
367
Mitigation against the event merapi
river channels cleared to contained lahars
mitigation against vunerability merapi
evacuation
gradual improvements to monitoring
BNBP est 2008 to monnitor voclanoes
mitigation against losses merapi
limited resourced from gov
temporary shelters in safe zones
subsistance farmes (no food)
How is a mid ocean ridge formed
Plates seperated by slab pull and ridge push
Magma rises from decompression
Magma solidifies into pillow lava
Causes creation of mid ocean ridge
Why do people not move from techtonically active regions
stasis
What can the Hawaiian islands and indonesian islands be called
Archipelago
When was the merapi eruption
2010
When was the etna eruption
2016
Buildings in haiti
Built out of breezeblocks to protect agianst hurricaines
What is the risk equation
risk= vulnerability/capicity to cope
How often does the earth polarity change
every 500,000 years
Extra paleomagnetism facts / sea floor spread
new rocks either side of mid ocean ridge
creates ridge push
alignment of iron particles in rocks settle as rock solidifies