geog book 4 chap 2

Question 1

what is an earthquake

Answer 1

the shaking of the Earths ground due to sudden release of energy in the Earths lithosphere
generally pccurs along plate boundaries and contain faults

Question 2

how do earthquakes occur

Answer 2

1. Rock mass on one side of fault are pushed by tectonic forces
2. friction causes rocks to get locked causing stress to build up
3. when the stres exceeds the strength of the fault, rocks snap to a new position
4. sudden movement causes seismic waves to be released causing ground shaking

Question 3

what is the focus

Answer 3

point on earths crust where seismic waves are released

origin of the earthquake

Question 4

what is the epicentre

Answer 4

point on earths directly above the focus
shaking is generally felt the most strength here

Question 5

what are seismometers

Answer 5

sensitive instruments that detect ground vibrations and determine the magnitude of an earthquake

the higher the seismic energy released during an earthquake, the higher the magnitude

Question 6

what is rhe richter scale

Answer 6

calculates earthquake magnitude using the height of the largest wave recorded on seismoneters and max seismic intensity reached rather than total seismic energy released

scale is logarithmic and is from 1-10

Question 7

what is the limitation of the richter scale

Answer 7

would rate an earthquake with a single drastic spike in wave energy to have a higher magnitude than a long earthquake with many large and intense waves and underestimates longer earthquakes that release more overall energy that may cause more damage

hence it is not commonly used except for small local earthquakes

Question 8

what is the moment magnitude scale

Answer 8

rates earthquake magnitude based on estimated total energy released during the earthquake

more accurate especially for earthquakes with magnitude 8 and above

thus scientists have adjusted magnitudes of past earthquakes such as the 1964 Prince William Sound Earthquake in Alaska from magnitude 8.6 to 9.2

scale is logarithmic

Question 9

what is a volcano

Answer 9

a landform created when lava erupts onto the earth’s surface

may form a cone-shaped mountain as more lava erupts and accumulates over time

eruptions occur at dpb and cpb

Question 10

how do tectonic processes at dpb result in volcanic eruptions

Answer 10

plates move apart causing the crust to stretch and fractures to develop

the decrease in overlying pressure causes parts of the underlying mantle to melt forming magma

magma contains dissolved gases and less dense than the surrounding materials

magma rises through weak areas in the crust to the earth’s surface and erupt as lava causing a volcanic eruption

lava cools and solidifies over time forming a volcano

Question 11

how do tectonic processes at cpb result in volcanic eruptions

Answer 11

plates move towards each other and the denser plate subducts under the other

subducting plate sinks into the mantle and the high pressure forces water out of the oceanic crust

water lowers the melting point of overlying mantle causing it to melt forming magma

magma contains dissolved gases and is less dense than surrounding materials

hence magma rises through weak areas in the crust to the earths surface and erupt as lava causing a volcanic eruption

lava cools, solidifies and accumulates over time forming a volcano

Question 12

what is high silica magma?

Answer 12

usually associated w stratovolcanoes
more viscous

as magma rises to the earths surface, dissolved gases in the magma cannot escape easily

more pressure builds up until gases escape explosively causing violent and explosive eruptions

Question 13

give an example an explain a volcano with viscous magma yet does not result in an explosive reaction

Answer 13

Mt merapi is a stratovolcano but its eruption in 2006 was not explosive as viscous magma rose in a way that allowed dissolved gases to escape easily

Question 14

what is low silica magma

Answer 14

usually associated with shield volcanoes

less viscous

as magma rises to the earths surface dissolved gases in the magma can escape easily

less pressure builds up resulting in gentle effusive eruptions

Question 15

explain the formation of stratovolcanoes and name an example

Answer 15

high viscosity magma rises through weak areas in the crust to the earths surface and erupts explosively as lava, ash and rocks

ash and rocks settle on the sides of volcano and are later covered by lava

over successive eruptions, a tall volcano consisting if alternating layers of ash and lava develops

as high viscous lava travels a shorter distance before cooling and solidifying, volcano has steep sides and narrow summit

Mt Mayon Philippines

Question 16

explain the formation of shield volcanoes and name an example

Answer 16

low viscosity magma rises through weak areas in the earths crust to the earths surface and erupts effusively

over successive eruptions, a volcano consisting of layers of lava develops

as the low viscosity lava travels a longer distance before cooling and solidifying, causing the volcano to have gentle sloping sides with a broad summit

Kilauea Hawaii

Question 17

name the structure of a volcano

Answer 17

1. magma chamber
2. layers of rock
3. pipe/ conduit
4. layers of ash
5. layers of lava
6. lava flow
7. vent
8. volcano cone
9. secondary cone
10. crater
11. pyroclasts

Question 18

what is a magma chamber

Answer 18

a reservoir of molten rock beneath the Earth’s crust

as more magma seeps into the magma chamber,
pressure in the magma chamber builds up
giving rise to a volcanic eruption

Question 19

what is a pipe/conduit

Answer 19

where magma flows from magma chamber to vent

Question 20

what is a vent

Answer 20

opening in the earth’s surface with a pipe leading into magma chamber

Question 21

how is the secondary cone formed

Answer 21

during formation of the volcano the vent may be blocked

forcing magma to find new exit route to surface

secondary cone of newer mantle material develops

Question 22

what are pyroclasts

Answer 22

ash and rock fragments and volcanic bombs ejected during volcanic eruption

mixed with superheated gas, form pyroclastic flow which can reach up to 200m/s

becomes lahar when mixed with water of melted snow/ice causing fast moving mudflow if 40m/s

Question 23

how is a caldera formed

Answer 23

the summit of a volcano may be blown off durint an explosive eruption

sides of the crater may collapse inwards due to loss of structural support

creates a much larger crater than original volcanic vent

a caldera, large basin-shaped volcanic depression is formed

over time, magma chamber beneath caldera solidifies and volcano bexomes extinct

caldera may then fill with water to form a lake

Question 24

how are volcanic eruptions measured?

Answer 24

volcanic explosivity index measures magnitude if different volcanic eruptions based om explosivity

the greater the vol of ejected material -> higher VEI

the greater the height of eruption cloud -> higher VEI

the longer the duration of eruption -> higher VEI

measured on a scale of 0-8
- effusive 0 or 1 as they are non explosive with less than 0.0001km³ of material ejected
- value of 8 -> mega-colossal explosive eruption, eject more than 1000km³ of tephra and eruption cloud column height of over 25km

scale is logarithmic

Question 25

how are earthquakes distributed

Answer 25

occur along all types of PB largest conc of earthquakes r at PRoF at PB, plates are pushed by tectonic forces causing stress to build up and energy to be released - narrow belt of eq along CPB in PRoF - narrow belt of eq along DPB at MAR - narrow belt of eq along TPB at SAF eq occur more commonly along CPB at subduction zone as mo4e stress builds up during eq an exception are eq that occur away from PB - eg within Eurasian Plate

Question 26

what is PRoF

Answer 26

broad belt around the Pacific Ocean where most eq and active volcanoes occur compromise of all 3 types of PB CPB: pacific & philippine DPB: pacific & cocos TPB: pacific & na at saf

Question 27

how are volcanoes distributed

Answer 27

generally located near cpb and dpb at these pb, magma rises to the surface forming volcanoes belts of volcanoes observed along - CPB: belt of volcanoes along subduction zones at PRoF - DPB: belt of volcanoes along DPBs between NA and EUAS plates unlike eq, volcanoes not found near TPB and CC-C (magma does not rise to the surface) hotspot volcanoes are exceptions found away from PB

Question 28

name an example of a hot spot volcano

Answer 28

Piton de La Fournaise is a HSV located on the island of Reunion in Indian Ocean away from PBs

Question 29

how are tectonic hazards distributed - eq

Answer 29

often localised generally located within same geographic region as the eq as eq are found along pb, hazards are also found near pb

Question 30

how are tectonic hazards distributed - volcano

Answer 30

volcanic hazards generally found near volcanoes at DPB and CPB however not all are localised - tsunamis & volcanic ash may spread beyond geographic regions where eq and volcanoes are located > may travel thousands of km > tsunami: travel great distances without loss of energy > ashfall: depends on wind conditions and vol of ash erupted and height of ash thrown into atmosphere

Question 31

give an example of ashfall spreading away from volcanic eruption

Answer 31

eruption of mt pinatubo 1991 resulted in ash spread across SEA

Question 32

what are the earthquake hazards

Answer 32

ground shaking soil liquefaction landslides tsunamis

Question 33

what are the volcanic eruption hazards

Answer 33

tephra volcanic gases lava flows pyroclastic flows lahars volcanic islands

Question 34

what are the impacts of ground shaking on natural and human systems

Answer 34

1. destroys ecosystems - ruptures oil and chemical factories polluting land and water - ruptures and uproot trees causing widespread tree injury and death and damaging wildlife habitats 2. destroys properties and infrastructure - weakens buildings, bridges, roads and railways causing them to collapse and makes it difficult to rescue people 3. disrupts services - snaps water and gas pipes causing water shortages and disruptions to gas supply - electricity & comms cables break affecting important systems such as tsunami warnings and tv broadcasts 4. causes injury and fatalities - people may get trapped under collapsed buildings & infrastructure causing loss of life and injuries

Question 35

give an example of the impacts of ground shaking

Answer 35

2010 haiti eq surrounding areas around factories polluted debris polluted areas more than 250 000 houses collapsed due to violent vibrations about 220 000 people killed water pipes ruptured causing water shortages

Question 36

what is soil liquefaction

Answer 36

occurs when the violent ground shaking causes saturated, loose soil to lose its soil structure and transforms into a thick fluid

Question 37

what are the impacts of soil liquefaction on human and natural systems

Answer 37

1. destroys ecosystems - trees on liquefied soil sink and tip over damaging habitats and causes loss of biodiversity - liquefied soil may enter rivers causing aquatic plants to die - sewage pipes may be broken and untreated waste materials can pollute rivers killing aquatic species 2. destroys properties and infrastructure - buildings and infrastructure can sink in a tip over causing damage that makes it difficult to rescue people 3. disrupts services - electricity and comms cables and water and gas pipes can sink in and snap disrupting supply of these services - roads ans railways above liquefied soil can sink in and get damaged making rescue diffucult 4. causes injuries and fatalities - people may get trapped under collapsed buildings

Question 38

give an example of soil liquefaction impacting human and natural systems

Answer 38

2010-2011 Christchurch NZ eqs triggered severe liquefaction as city lies above former swamp area where soil is loose and saturated more than 60 000 residential buildings and infrastructure covering 1/3 of city damaged liquefied soil entered rivers and untreated sewage from broken pipes polluted rivers causing loss of biodiversity

Question 39

what are landslides

Answer 39

occur as the violent vibrstions from cracks on steep slopes loosen the rocks and soil, and trigger the loose rocks and soil downslope

Question 40

what are the impacts of landslides on human and natural systems

Answer 40

1. destroys ecosystems - fast-moving debris can bury huge areas of forests and wetlands - rivers can be polluted w debris killing aquatic life - rivers can be blocked causing floods that can damage nearby ecosystems and properties 2. destroys properties and infrastructure - debris can bury village and farms destroting properties and infrastructure 3. disrupts services - debris snap electricity cables water and gas pipes disrupts supply of these services - roads and railways can be blocked by debris difficult to rescue people 4. causes injuries and fatalities - debris can bury people - debris can block rivers drowing ppl

Question 41

give an example of landslides and its impact on the natural and human systems

Answer 41

2018 Papua New Guinea eq mw 7.5 triggered landslides and caused high amounts of debris to enter rivers caused flooding polluted waters and killed fish

Question 42

what are tsunamis

Answer 42

a series of ocean waves which can be caused by undersea earthquakes tsunamis can travel over thousands of km and devastate huge areas of coastline

Question 43

how do tsunamis occur

Answer 43

1. undersea eq causes seabed to be displaced 2. a large vol of water is lifted forming waves of great wavelength and low height of less than 1m 3. the waves travel towards land at high speeds - 800km/h 4. on approaching the coast, greater friction with shallower seabed slows waves down 5. the waves get closer together and higher in height 6. before a tsunami occurs - seabed may recede from the shore as sea water fills in the void caused by displacement of seabed

Question 44

give characteristics of a tsunami

Answer 44

can reach up to 15m or more in height travel at a speed of 30-50km/h devastate shorelines as the waves hit

Question 45

what are the impacts of tsunamis on human and natural systems

Answer 45

1. destroys ecosystems - seawater can flood huge areas of coastal wetlands and forests damaging habitats - large amount of debris carried by the waves can pollute these areas damaging ecosystems and killing wildlife 2. destroys infrastructure - fast moving waters and large amt of debris carried in by the waves can sweep away buildings and destroy them 3. disrupts services - fast moving waters and the large amount of debris carried in by the waves snap electricity and comms cables -> disrupting supply - " sweep away roads roads and railways making rescue difficult 4. injuries and loss of lives - sweeping waters can drown ppl - large amts of debrid carried in by waves can hit and kill ppl

Question 46

give an example of a tsunami impacting human and natural systems

Answer 46

2011 tohuku eq mw 9.0 triggered a tsunami up to 40m in height waves destroyed buildings tsunamis carried debris inland causing flooding and pollution Sendal suffered extensive damage and half its population killed 70 000 pine trees knocked down in Iwate causing biodiversity loss tsunami hit pacific islands devastating ecosystems

Question 47

what are the impacts of tephra on human and natural systems

Answer 47

1. destroys ecosystems - ash can be carried thousands of km by prevailing winds polluting huge areas of ecosystems - ash can infiltrate and kill wildlife - ash can cause blindness to birds 2. destroys buildings - volcanic bombs can hit properties damaging them - ashfall accumulates on roofs - when saturated with water, ash can double in height causing roofs to collapse - corrosive, weakening building structures -> more likely to collapse - thick blankets of ash damage farmland suffocating crops and destroying livelihoods 3. disrupts services - ash particles can damage plane engines -> closure of airspaces and disruption of air transport 4. causes injury and fatality - volcanic bombs can hit people causing injury and loss of lives - ashfall can cause respiratory problems, eye irritation and suffocation

Question 48

give an example of tephras impact on natural and human systems

Answer 48

1991 mt pinatubo eq emitted huge amts of ash buried more than 180km² of forests in 25cm ash destroyed 800km² of rice fields affecting livelihoodd of many farmers airports closed and many flights cancelled disrupting transport some places damaged

Question 49

what are the impacts of volcanic gas on natural and human systems

Answer 49

can release large amts of toxic gases such as co2 and so2 1. destroys ecosystems - so2 results in acid rain when it reacts with water in air -> damaging vegetation soil & kill wildlife - cold co2 heavier than aif -> becomes concentrated in low-lying volcanic areas - higher amt of co2 in air -> kill wildlife and destroy vegetation 2. destroys properties and infrastructure - so2 results in acid rain corroding buildings and infrastructure 3. threatens public health & security

Question 50

give an example of volcanic gas having impact on natural and human systems

Answer 50

1979 Dieng Volcano eruption Indonesia - released deadly amts of co2 and killed 150 ppl

Question 51

what are the impacts of lava flows on natural systems and environment

Answer 51

extremely hot and can travel distances within geographic region deaths by LF are low as people can easily move away 1. destroys ecosystens - hot low silica lava can travel distances destroying forests and other habitats and ecosystems 2. destroys properties and infrastructure - lava can burn through homes properties and structures 3. disrupts services - lava can destroy electricity and comms cables water and gas pipes disrupting supply of these services

Question 52

give an example of lava flows impacting natural and human systems

Answer 52

2018 Kilauea eruption in Hawaii far reaching LFs destroying >600 homes destroyed huge areas of forests and ecosystems telephone and power lines damaged causing widespread comms outages

Question 53

what are pyroclastic flows

Answer 53

hot cloud of gas, ash and rocks travelling down slopes of volcano at great speeds >200kmh occur when a column of hot ash and gas gets thrown up into the air and falls back to the ground under the pull of gravity temp of up to 700°C making it the most devastating volcanic hazards travels several km

Question 54

how does pyroclastic flows impact natural & human systems

Answer 54

1. destroys ecosystems -huge areas of forests destroyed causing biodiversity loss - thick layers of ash cover the path of the flows polluting huge areas of forests 2. destroys properties and infrastructure - hot flows burn through HPI in their path 3. disrupts services - hot flows can destroy electricity and comms cables disrupting supply of these services 4. injuries and fatalities - extreme temps burn and kill ppl instantly

Question 55

give an example of pyroclastic flows impacting natural and human systems

Answer 55

2010 merapi eruption Indonesia blasted a series if PFs down slops inhabited by villagers about 350 deaths huge areas of forests burned

Question 56

what are lahars

Answer 56

mudflows comprising water and ash formed when huge amts of rain and rocks ejected during an eruption mix with water can flow at high speeds of up to 200kmh and cover considerable distances within geographic region

Question 57

how are lahars formed

Answer 57

PFs melt ice, snow and mix with water on volcanic cone as they travel down intense rainfall washes down ash

Question 58

what are the impacts of lahars on natural and human systems

Answer 58

1. destroys ecosystems - lahars can cover forests and other ecosystems with mud that hardens destroying them - can pollute rivers killing aquatic life 2. destroys properties and infrastructure - can bury homes and buildings, destroying them - can cober farms with mud that hardens damaging them 3. disrupts services - roads and railways blocked by debris making it difficult to rescue ppl - can damage comms cables and water and gas pipes disrupting supply of services 4. TPB and IF - can bury houses & its residents causing LoL

Question 59

give an example of lahars impact on natural and human system

Answer 59

1985 nevada del ruiz eruption in columbia released huge amts of ash and volcanic ash melted snow and ice meltwater mixed with ash and rocks form lahars fast-moving lahars buried more than 20000 ppl instantly rivers highly muddied by lahars killing many fish

Question 60

what are volcanic landslides

Answer 60

common on tall and steep volcanic cones comprising thousands if solidified lava layers and loose tephra blast from an explosive eruption trigger downward movement of loose volcanic materials causing a landslide high velocity and great momentum of landslides allow them to travel considerable distances in the geographic region

Question 61

what are the impacts of volcanic landslides on natural and human systems

Answer 61

1. destroys ecosystems - fast moving debris can bury huge areas of forests and wetlands - debris from landslides pollutes rivers killing aquatic life - debris block rivers causing fliids and damaging nearby ecosystems and properties 2. destroying properties and infrastructure - debris bury villages and farms destroying properties and infrastructurr 3. disrupts services - debris can snap electricity and comms cables and water and gas pipes disrupting supply - debris can block railways and roads -> difficult for rescue 4. CIF - debris can hit ppl causing injuries and LoL - debris block rivers causing flooding drowning people

Question 62

give an example of volcanic landslides impacting natural and human systems

Answer 62

1980 mt st helens usa north face of volcanic cone collapsed causing landslides that travelled 23km destroyed huge areas of land and killed many

Question 63

explain the benefits if volcanic eruptions and living near volcanoes - farming

Answer 63

over thousands of years, volcanic rocks break down and undergo weathering to form fertile soils ss they produce high crop yields and locals benefit from it

Question 64

explain the benefits if volcanic eruptions and living near volcanoes - extracting precious materials and fossil fuels

Answer 64

magma cools and solidifies beneath volcanoes forming precious materials source of income for locals employed to mine them govt can sell them to generate revenue can be used to provide social services to locals volcanic materials such as ash and solid materials may also be mined and used as construction materials

Question 65

explain the benefits if volcanic eruptions and living near volcanoes - harnessing geothermal energy

Answer 65

derived from heat in earths crust can be harnessed in tectonically active areas beneath earth's surface hot rocks heat up groundwater forming steam harnessed to generate energy locals benefit from cheaper local energy and can be employed to work at geothermal power plants

Question 66

explain the benefits if volcanic eruptions and living near volcanoes - tourism activities

Answer 66

tectonic movements can be attractive to tourists such as hiking and sightseeing provides locals w employment opportunities such as tour guides, sellinf products and providing accommodation hence boosting local economy

Question 67

give an example of the benefit of farming with fertile soil at volcanic regions

Answer 67

best rice-growing regions in indonesia are near volcanoes in Bali -> Mt Agung

Question 68

give an example of the benefit if extracting precious minerals and fossil fuels

Answer 68

at mt merapi, thousands of locals employed to mine volcanic sand suitable for construction

Question 69

give an example of the benefit of harnessing geothermal energy

Answer 69

iceland: most electricity generated from geothermal power plants

Question 70

give an example of the benefit of tourism activities at volcanic regions

Answer 70

Hawaiian islands are popular tourist locations for it scenic volcanic landscapes and tourism generates an annual income of ~usd 8mil and provides locals w thousands of jobs