the challenge of natural hazards

Question 1

what are natural hazards?

Answer 1

natural hazards are natural events such as earthquakes that have the potential to do damage to humans and property

Question 2

list 4 hazards

Answer 2

tectonic, atmospheric, biological, geomorphological

Question 3

list the three things that affect hazard risk

Answer 3

vulnerability, capacity to cope, nature of hazard

Question 4

vulnerability:

Answer 4

the larger the population exposed the greater risk

Question 5

capacity to cope:

Answer 5

LICs (low encome countries) are particularly at risk as they do not have the money to protect themselves

Question 6

nature of hazard:

Answer 6

the type, frequency and magnitude of a hazard affects the level of risk

Question 7

what are the four layers of the earth from the outside to the inside?

Answer 7

crust, mantle, outer core, inner core

Question 8

the crust:

Answer 8

varies in thickness(5-10km) beneath the ocean. made up of several large plates.

Question 9

the inner and outer core:

Answer 9

hottest section (5000 degrees). mostly made of iron and nickel and is 4x denser than the crust. the inner layer is solid whereas the outer layer is liquid.

Question 10

the mantle:

Answer 10

widest layer (2900km thick). the heat and pressure means the rock is in a liquid state that is in a state of convection

Question 11

what is the crust split up into?

Answer 11

major fragments called tectonic plates

Question 12

how many types of tectonic plates are there?

Answer 12

2- oceanic and continental

Question 13

Oceanic tectonic plate:

Answer 13

thin 5-10km, dense so sinks under continential crust, young 70-100 million years old, basalt rock and continually renewed and destroyed.

Question 14

Continental tectonic plate:

Answer 14

thick 20-200km, less dense, old 3.8 billion years old, granite and not destroyed.

Question 15

How tectonic plates move?

Answer 15

these plates move due to convection currents in the mantle and where they meet tectonic activity (volcanoes and earthquakes) occur.

Question 16

How are earthquakes caused?

Answer 16

Earthquakes are caused when two moving plates (convection currents) become locked causing friction to build up. from this stress, the pressure will eventually be released, triggering the plates to move into a new postion. this movement causes energy in the form of seismic waves, to travel from the focus towards the epicentre. as a result, the crust vibrates triggering an earthquake.

Question 17

what is the epicentre?

Answer 17

the point directly above the focus, where the seismic waves reach first, is called the epicentre.

Question 18

What are seismic waves?

Answer 18

seismic waves are energy waves that travel out from the focus.

Question 19

the distribution of tectonic activity

Answer 19

along plate boundaries in narrow linear zones e.g. pacific ring of fire. earthquakes occur at all 3 types of margins but volcanoes are only found at destructive and constructivemargins allthough some volcanoes can be over hotspots away from plate boundaries e.g. hawaii.

Question 20

what is a destructive plate margin?

Answer 20

(compressional-Nazca and South American plates) Here two plates are moving together (slab pull). When the denser plate subducts, friction causes it to melt and become molten magma. the magma forces its way up to the surface to form a volcano e.g. Cotopaxi. This margin is also responsible for devastating earthquakes, explosive eruptions, fold mountain ranges e.g. Andes and ocean trenches e.g. peru - chile.

Question 21

what is a constructive plate margin?

Answer 21

(tensional - North Amercian and Eurasian plates) Here 2 plates are moving apart (slab push) causing new magma to reach the surface through the gap. volcanoes formed along this crack cause a submarine mountain range such as those in the Mid Atlantic Ridge.

Question 22

what is a conservative plate margin?

Answer 22

(passive-North American and Pacific Plates) Plates slide past each other in opposite directions, or in the same direction but at different speeds. this is responsible for earthquakes e.g. San Andreas fault, USA.

Question 23

what is used to measure an earthquake?

Answer 23

a seismometer producing a seismograph.

Question 24

What does the magnitude (richter) scale measure?

Answer 24

the amount of energy released on a logarithmic scale.

Question 25

What does the Mercalli scale measure?

Answer 25

the visual effects and the amount of damage

Question 26

what is a primary effect?

Answer 26

a primary effect is what occurs directly due to the tectonic hazard

Question 27

what is a secondary effect?

Answer 27

a secondary effect is what happens as a result of the primary effect

Question 28

what are the two types of responses to tectonic hazards?

Answer 28

immediate (short term) and long term

Question 29

list 6 reasons why effects and responses differ

Answer 29

population density, magnitude, primary/secondary effect, time of the year/day, monitoring/prediction, training of emergyency services

Question 30

list the 4 things that can be done to reduce the impact of tectonic hazards

Answer 30

monitoring, prediction, protection, preparation/planning

Question 31

explain how monitoring can be done

Answer 31

seismometers/GPS measure earth movement . radon gas meters are used . warning system can give some warning time.

Question 32

explain how prediction can be done

Answer 32

by observing data and historical records, to forecast an event. Haicheng 1975, unexplained animal behaviour saved an estimated 150,000 when a magnitude 7.3 quake struck.

Question 33

what is the focus?

Answer 33

the point at which pressure is released is called the focus.

Question 34

explain how protection can be done?

Answer 34

reinforced building e.g. The Tans-America building. Making building foundations that absorb movement. Auto shut offs for gas and electricity.

Question 35

explain how preparation/planning can be done?

Answer 35

by avoiding building in at risk areas. training for emergency services and planned evacuation routes/assembly areas and drills, emergency supplies can be stockpiled in advance. educate people on how to react at home/in work.

Question 36

what is global atmospheric circulation?

Answer 36

Atmospheric circulation is the large-scale movement of air by which heat is distributed on the surface of the earth.

Question 37

where are the suns rays most concentrated?

Answer 37

at the equator

Question 38

what happens as the air heats?

Answer 38

it rises causing low pressure(wet). as it cools, it sinks, causing high pressure. Winds move from high to low pressure. they curve because of the Coriolis effect (the turning if the earth)

Question 39

what is a hadely cell?

Answer 39

the largest cell which extends from the equator to 30-40º. air heats, rises condenses forming rain and separates before descending at 30-40º.

Question 40

What is a Ferrel Cell?

Answer 40

the middle cell where air sinks over deserts and flows towards the 50º. this warm air hits cold polar air, rises giving rain over the UK (50ºN) some air moves poleward/equator wards.

Question 41

what is a polar cell?

Answer 41

the smallest cell occurs 60-90º north and south. rising air over (50º) moves towards the Poles and sinks at the poles moving towards the equator.