Hazardous Earth Flashcards

Question

what are the characteristics of explosive eruptions?

Answer 1

Trapped gas bubbles burst violently when magma reaches surface - vent and top of cone often shattered Rhyolitic and andesitic Silica, high viscosity 700-1000 degrees Lava, gases (water vapour, CO2, N, SO2), pyroclastic material (tephra - dust, ash, lava bombs) Sporadic - long periods with no activity Steep-sided composite volcanoes - stratovolcanoes, calderas Usually convergent, but can happen at divergent/hot spot Mount ontake, Japan 2014

Answer 2

Gas bubbles escape easily, lava flows freely with limited explosive force Basaltic Mafic, low viscosity >1000 degrees Lava, gases (water vapour, CO2, N, SO2) Regular - eruption can continue for months/years Shield volcanoes with gentle slopes - lava plateaux Divergent and hot spots Geldingadalur, Iceland 2021

Answer 3

Results from mantle plumes reaching the base of the lithosphere Causes partial melting and an area of volcanic activity - hotspot Plume is stationary when the plate moves over it, leading to a chain of volcanoes which become extinct when transported away. Associated with basaltic lava, shield volcanoes and flood basalts

Answer 4

linear volcanic vents through which lava erupts effusively (cause flood basalts and lava plateaux)

Answer 5

Dominant lava chemistry and eruption style of single volcanoes can change over time and larger volcano have smaller cones on their flanks

Answer 6

alternating layers of tephra and viscous lava pile up near the vent, forming conical shape with steep sides. No more than 10 km diameter but can exceed 3000 m in height, 30 degrees slope

Answer 7

layers of low-viscosity lava flow far from the vent, giving a broad, rounded shape with gentle slopes, 5 degrees, varies in size largest 100 km wide

Answer 8

volcano that has erupted >1000 km2 of material in a single event, highly explosive, eject so much magma that the chamber is emptied and volcano collapses on itself forming a caldera

Answer 9

Volcanic explosivity index

Answer 10

magnitude of volcanic eruptions to compare them

Answer 11

volume of material ejected, eruption plume height and qualitative descriptions to assign a value from 1-8 Each increase is a 10 fold increase in explosivity 8 = supervolcano

Answer 12

Icelandic eruptions - VEI 0 - effusions of basaltic lava flow from fissures - lava plateaux Hawaiian eruptions - VEI 0-1 - flow from single vent and flank fissures to form shield Strombolian eruptions - VEI 1-2 - mildly explosive but frequent eruptions of gas/tephra Plinian eruptions - VEI 4-8 - extremely explosive - immense eruption clouds and eject huge volumes of pyroclastic materials

Answer 13

Lithosphere is constantly under stress from tectonic forces - causes build up of strain energy Stress overcomes strength of rock causing faults Some intraplate earthquakes occur due to faults

Answer 14

fountain of hot and cold water as well as steam that are ejected from the ground at great speed. shoot up into the sky up to 100m.

Answer 15

water underground is heated by magma that is nearby and the water becomes hot. superheated water - temperature can be >100 degrees as it is under pressure. theory that a chamber of water being heated by rocks. linked to the surface by a narrow vent. pass the boiling point of water and becomes steam which then explodes and forces water up the vent.

Answer 16

Hot water from underground comes to the surface. temperature needs to be above human body temp.

Answer 17

wherever groundwater is heated by magma underground.

Answer 18

vents giving off steam and volcanic gases

Answer 19

occur wherever superheated water reaches the surface and gases come out of solution and bubble off.

Answer 20

what is left of a magma chamber that has cooled and formed granite that is hard to erode. other rock around is easier to erode and crust level has dropped so the igneous rock is left sticking up out the ground. only eroded by huge glaciers.

Answer 21

magma forced into crustal rocks - intruded. happens when fold mountains are formed causing rock to melt and over time builds up in mass beneath surface and then cools and solidifies.

Answer 22

igneous rock - granite/basalt/etc. looks like sea wall. harder rock that has been exposed as surrounding weaker rocks have been weathered and eroded. as land surface drops harder rock left behind.

Answer 23

discordant as magma gets in to rock and stick up from layers. cuts across rock vertically.

Answer 24

huge and small features. magma has intruded into rock and follows the lateral pattern of the rock solidifying in layers. surrounding rock gets worn down and harder resistant rock is left behind.

Answer 25

concordant - follow pattern of rock. whin sills formed.

Answer 26

Hawaii July 2015 20km flow. 800m in one day. Basic (basaltic) lava is free-flowing and can run for large distances. acidic lavas such as rhyolite are thick and pasty so do not flow easily

Answer 27

dependent on type of lava. everything in the path of lava will be burned, bulldozed or buried. destroy infrastructure, property, crops. lava flows rarely cause injuries or fatalities.

Answer 28

Pompeii AD79 M. Vesuvius combination of hot gases (500 degrees+), ash and rock fragments travelling at high speed (100km/hr).

Answer 29

follow contours of the ground and destroy everything in their path. The inhalation of such hot and poisonous gas and ash causes instant death.

Answer 30

Eyjafjallajokull volcano April 2010 cancelled 100,000 flights. any material ejected from a volcano into the air. Ranges in size from very fine ash to volcanic bomb (>6cm across). includes lighter debris such as pumice.

Answer 31

very hazardous, burying farms in layers of ash and destroying crops. Transport can be disrupted both on the ground and in the air. buildings collapse due to weight of ash and people with respiratory diseases can struggle to breathe.

Answer 32

including CO, CO2 and SO2 eruptions emit a wide range of toxic gases.

Answer 33

deadly and silent threat to humans, when SO2 combines in atmospheric water, acid rain is produced. enhances weathering and damages crops and pollutes surface water and soils.

Answer 34

1984 Nevado del Ruiz, Columbian town of Armero overwhelmed. 23,000 died. type of mud flow with the consistency of wet concrete. snow and ice on a volcano summit melt during an eruption and flow rapidly down the cone. Rock fragments large and small, as well as ash and soil, are mixed together. can travel 50km/h.

Answer 35

everything in their path is either destroyed or buried under thick layers of debris. after rainfall hazards can remain.

Answer 36

Iceland, several active volcanoes lie under th Vatnajokull ice field. volcanic eruptions beneath an ice field or glacier cause rapid melting. vast quantities of water accumulate until they find an exist. causes a torrent of water.

Answer 37

devastating floods

Answer 38

mt St Helens - biggest landslide in recorded history at the time as magma is forced up and the ground bulges, dome collapses and causes landslides. also may happen as ash lands on slopes and collapses as too heavy forcing a slide.

Answer 39

localised damage

Answer 40

Krakatoa 1883 is believed to have drowned 36,000 people. Characteristics - violent eruption of some island volcanoes can cause massive displacement of ocean water and tsunami waves capable of travelling up to 600 km/h. In deep water they have a height that is less than 1m and a long wavelength of 200 km. approaching the shore, waves increase in height and when they break transfer vast amounts of energy and water along the shore and inland.

Answer 41

devastating flooding and loss of life and infrastructure

Answer 42

0-70 km focal depth All plate boundaries and intraplate locations Evidence lithosphere is divided into plates Stronger ground haking at surface Gound shaking concentrated into smaller area E.g. Kashmir, Pakistan 23 km, M 7.5, deaths >87,000

Answer 43

70-700 km focal depth Destructive plate boundary Evidence for existence and nature of subduction Weaker ground shaking as seismic waves decreased with distance from focus Shaking over wide areas because waves spread out as they move away from focus Hindu Kush, Afghanistan 212 km, M 7.5, deaths 399

Answer 44

amount of energy an earthquake releases - each only has one

Answer 45

Richter scale - energy released using maximum amplitude of seismic waves recorded on seismogram Moment magnitude scale - additional parameters (size of fault rupture and rock strength) to increase accuracy - main scale used, each increase = 10-fold increase in shaking and a 32-fold increase in energy release, however, logarithmic scale which makes it difficult for the public to understand - prevents preparedness

Answer 46

amount of ground shaking in a specific location depends on: Magnitude Distance from epicentre and focus Rock and soil characteristics Resistance of buildings/infrastructure to ground shaking

Answer 47

Modified Mercalli intensity scale 12-point scale based on qualitative descriptions of shaking felt and observed impact on built environment Intensity of single quake observed in many locations can be plotted on map using isolines Depends on human perception, vary and reduce accuracy - more useful than magnitude in assessing impact

Answer 48

Earthquakes occur only faults, (brittle fractures in lithosphere), rock on either side is displaced, sometimes by metres at a time - dramatic and widespread effects Lithosphere stretched at divergent, faults dipping towards each other develop parallel to the margin. Land between blocks either side are elevated - creating a rift valley e.g. East African Rift Steep slope formed where fault breaks the surface forms an escarpment - help form fold and thrust mountains

Answer 49

when they affect people

Answer 50

ground shaking and displacement - moves vertically and horizontally - shaking intensity depends on magnitude, distance from epicentre and focus and geology

Answer 51

ground shaking

Answer 52

Liquefaction - when violently shaken, unconsolidated deposits (sand/slit on floodplain) with high water content lose mechanical strength and become fluid Landslides and avalanches - shaking can trigger slope failure and mass movement, the 2015 Nepal earthquake caused >21,000 landslides and avalanches on Mount Everest Tsunamis - giant waves from large, sudden displacement of sea water, usually underwater earthquakes which cause seabed uplift (less often than volcanoes/landslides). Deep water wavelengths often >100 km, low wave height <1 m. when reaching shallow water/land they slow and increase in height. When 1st wave hits shore causes sea level to drop (drawdown), immediately behind is wave crest, travel several km inland. Flooding - indirectL trigger tsunamis, destabilising/destroying dams, destroying/lowering protective levees, causing landslides which dam rivers to create ‘quake lakes’ (dams can later collapse)

Answer 53

Earthquakes cause significantly more deaths than volcanoes Number of geophysical events has not changed over time The number of people living in hazardous areas has increased Number of geophysical disasters (earthquake, volcano or mass movement affecting >100 people) has increased over past 50 years with 30 per year today compared to half in 1960s Human activity may have increased secondary hazards

Answer 54

Degree of risk posed by a hazard is related to its magnitude, how often it occurs and level of vulnerability of the people living there Risk (R)= Frequency of or magnitude of hazard (H) x level of vulnerability (v)/capacity of the population to cope and adapt (c) R = HV/C

Answer 55

Generally, greater magnitude, less frequently it occurs High-magnitude, rare events release large amounts of energy and have the greatest impact on human populations Vulnerability is concerned with the ability of a community to withstand exposure to a hazard. Vulnerability increases risk

Answer 56

Stating exactly when and where an earthquake of a certain magnitude will occur is not possible, but research is ongoing

Answer 57

Uses seismic monitoring, historical records and fieldwork (e.g. GPS to measure ground deformation around fault zones) to estimate earthquake likelihood Can be used to improve adaptations - prioritising vulnerable locations for investment Developments of GPS-A - unmanned vehicles called wave gliders float at sea for months, detecting sea floor motion to help understand tsunamis

Answer 58

Major role in future mitigation with new techniques e.g. eco-friendly ductile cementitious composite (EDCC) Success depends on effective designs as well as adaptation to local cultural, economic and institutional factors that influence compliance with building codes Affordable, low-tech solutions can be used if funds are limited, 2007-2012 smart shelter foundation created 15 earthquake-resistant schools in Nepal which all survived the 2015 quake

Answer 59

Response = sequence of stages Disaster response curve (park model) Adjusted to fit and allow comparison between individual events

Hazardous Earth Flashcards

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