Natural Hazards Flashcards by Emily Bissett

What is a natural event

A natural event would occur on earth without people, they are events that naturally happen on our earth .

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What is a natural hazard

A natural hazard is when humans and livings things are present during these events which are a hazard towards us therefore becomes a ‘natural hazard’

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How are different natural hazards classified. (4)

Tectonic hazards- such as earthquake, tsunamis and volcanoes (due to earth structure- crust and tectonic plates)
Atmospheric hazards- such as hurricanes, droughts, snow storms (things that occur in the atmosphere)
Geomorphological hazards- flooding, avalanches, land slides (things that occur on earths surface)
Biological hazards- forest fires, animal and plant invasions (things that involve living organisms)

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Why are some natural hazards harder to categorise than others?

Their characteristics- e.g. Tsunamis are tectonic hazards but can also be geomorphological as landslides can displace a large body of water causing a tsunami

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How can human activity cause avalanches

People skiing on unstable, uneven areas of snow.
Building on these snowed grounds can create pressure and intense noise which causes vibrations therefore leading to an avalanche.
Global warming.

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Why do people live In places where natural hazards occur

GIVE EXAMPLE

E.G. JAVA IN INDONESIA 
Recourses- cheap geothermal energy&amp; fertile soil, minerals
Jobs
Optimistic it won't happen 
Over confident in defences 
Can't move- expensive, lack of knowledge and language barrier 
Housing is cheaper in these areas 
Tourism

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What is the crust

Outer layer of the earth

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What is a plate margin

The boundary where two plates meet

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What is mantle

The dense, mostly solid layer between the outer core and the crust

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What is a plate

Section of earths crust

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What are convection currents

Circular currents of heat rising and falling in the mantle, they move the plates.

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What are the two different types of crust

Continental- carries land

Oceanic- carries water

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Describe the movement in convection currents

Current heated rock in mantle rises as it’s less dense
Semi molten rock spreads out carrying the above plate with it
The mantle then cools and sinks back down to be reheated

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What are the 3 types of plate boundary

Example for each

Conservative- San Andreas fault
Constructive - Mid Atlantic Ridge
Destructive - Nazca Plate under South America Plate

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Describe what happens at a conservative boundary

The plates move sideways past each other.
Crust is neither created nor destroyed. When the 2 plates stick, pressure builds up which can be suddenly released and an earthquake can occur.

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Describe what happens at a constructive boundary

The plates are moving away from eachother, molten rock rises from the mantle below the crust which eventually cools and a new crust forms . Features around this type of plate margin are volcanos

Describe what happens at a destructive boundary

Two plates move towards eachother. The oceanic plate is denser and sinks under the continental plate. It is destroyed. As a result, deep ocean trenches are formed and volcanoes occur at the surface. On occasions the plates stick and pressure builds up, this may be released suddenly and an earthquake occurs.

What is an earthquake

An earthquake is a sudden violent movement (shockwave) within the earths crust.
They occur due to a release of built up pressure in the crust.

What is the focus point

The point within the earth where shockwaves start

UNDERGROUND

What is the epicentre

The point on the earths SURFACE above the focus. Earth quakes are felt the strongest there.

What are aftershocks

Smaller waves that occur after the initial movement. These may last months after th large quake

How do we measure earthquake activity

Levels 1 to 7 goes up by x10 each time

E.g. Level 1- 1 level 2- 10, level 3- 100

What can we use to measure how an earthquake feels (intensity &effects of shaking on people, structure and the environment)

The mercalli scale

Explain the characteristics of the mercalli scale

Is is qualitative data measured by the judgment of humans. It has 1-12 levels on the scale, the level of the quake increases evenly.
,

What can we use to measure the magnitude (strength of waves and vibrations being emitted)

The Richter scale

Explain the characteristics of the Richter scale

Quantitive datas, measured by an instrument called a seismometer. The number of levels on the scale is 1-10 and the level of quake increases logarithmically.

What is the damage done like on the mercalli scale and the Richter scale (comparison)

In the mercalli scale -Steering of cars affected Buildings damaged, including some damage to earthquake resistant buildings Cracks in ground However in the Richter scale- bridges destroyed, few structures left standing

Why do some earthquakes cause more damage than others (5)

Large urbanised areas- more things and People to get hurt and damaged Time of day- if an earthquake hits at rush hour then the large amount of people located in that certain area will be at a huge risk. Low income countries- poorly built houses, aren't equipped. Population density Depth of focus- deeper it is the less impact

Primary effects of earthquake activity

Collapsing buildings and bridges Cracked and twisted roads and other transport links Death and injuries to individuals Panic and shock of the people affected

Secondary effects of earthquake activity

Fires caused by broken gas mains and electrical cables Tsunamis Landslides Avalanches Disease and famine due to a lack of clean water and medical facilities

Immediate responses to earthquake activity

``` Getting under tables Get out of buildings Dig people out Emergency aid Rescue teams Sniffer dogs Heat sensing equipment ```

Long term responses to earthquakes

Rebuilding programs | Reconstruction

How can the risk of earthquake activity be reduced | 3ps

Predict Prepare Protect

First p- PREDICT | What does this involve and do

This involves monitoring activity- find earth quakes location- this also involves historical evidence to try to predict where and when another earthquake might occur

4 signs that suggest an earthquake might occur

- small foreshocks before main quake these can be measures with a seismograph - animals often react strangely (birds go silent and dogs howl) - small cracks develop in rocks, these can cause rocks to swell, bulge and fill with after due to changing water levels- Rodon gas will also Seep out. - most likely to occur after long period of time in which the plates don't move (pressure building)

Second p- PLAN/PREPARE | What can we do to plan and prepare

Radio stations and to stations must be prepared to give out earthquake advice Emergency plans for people who get injured Family emergency kits should provide food, clothing, a radio and torch Architects and builders must follow rules for a safe building Every month schools must practice a drill Hospitals and fire stations must not be built in earthquake zones

Explain how the structure of a building can be adapted to earth quakes and give an example. PROTECT

Steel frames that can sway during earthquake movement Birdcage like interlocking steel frame Outer panels flexibly attached to steel structure Fire resistant building materials Rubber shock absorbers to absorb earth tremors Automatic window shutters prevent falling glass. E.g. Transamerican pyramided shaped building