Physical Geography - Autumn Term

Key terms and definitions for A Level physical geography

Natural Hazards

a naturally occurring event that threatens a loss of life and/or damaging property and disruption to human activities` 

Geophysical natural hazards

volcano, earthquake, tsunami, avalanche and landslide

Biological natural hazards

Wildfires

Atmospheric natural hazards

Tropical storms, Tornado, Flood and Drought

Risk

people exposed to a hazardous event = potential threat to livelihood

Vulnerability

conditions such as physical, social, economic and environmental factors which increase susceptibility to a hazard impact

Factors affecting hazard perception

socio - economic status, level of education, past experiences, religion etc

What is prediction ?

using science and technology to predict when and where a hazard will happen 

What is adaption ?

changing behaviour to reduce potential losses

What is mitigation ?

working to reduce or prevent the occurrence of hazards

What is integrated risk management ?

analysing potential risks and implementing a coordinated approach to manage and reduce risks 

What is risk sharing ?

working together to reduce the risks and sharing the cost of hazard response

What are 4 responses to hazard perception ?

1. Fear - area so vulnerable that people move out of fear

2. Domination - adjustment so successful that people not impacted

3. Fatalism - God’s will, losses accepted as inevitable etc

4. Adaption - preparation depending on development of area

Why is the earth’s core so hot ?

radioactive decay of isotopes

Key facts continental plate

Density - 2.6g/cm3 lighter

Composition - mainly granite, silicone, oxygen and aluminium

Thickness - 30-70 km

Age - over 1500 million years

Key facts oceanic plate 

Density - 3 g/cm3 heavier 

Composition - mainly basalt, silicon, magnesium and oxygen 

Thickness - 6 - 10 km 

Age - less than 200 million years old 

How does slab pull happen ?

1. upwelling magma at divergent plate boundary constructs new crust ( hot with low density) ]

2. as new crust moves away from divergent boundary it cools ( more dense )

3. as old, cold, dense crust moves away from divergent boundary it sinks into mantle - this pulls rest of plate along behind it

What is geological evidence ?

physical traces and formation found in Earth’s crust, including rocks, minerals ,fossil and soil

What is climatological evidence ? 

various types of data and observations that indicate changes in Earth’s climate over time 

What is biological evidence?

any material collected from a living organism, making it a unique source as it contains genetic or cellular material

What is seafloor spreading ?

geologic process in which tectonic plates - large slabs of Earth’s lithosphere move apart from each other

What is evidence for seafloor spreading ?

rocks are carbon dated, the youngest rocks are closest to the mid ocean ridges

What is the Mercalli scale ?

based upon what people in the area feel and their observations around them

How are earthquakes measured ?

magnitude of an earthquakes is measured using seismometers

What are primary/pressure waves ?

fastest, reach surface first

act like sound waves - pushing and pulling in crust a high frequency through series of compressions

travel both the mantle and core

What are secondary/shear waves ?

half as fast as P waves but very damaging, they reach surface afterwards 

high frequency but shake laterally 90 degree angles of direction of movement 

What are surface love waves ?

slowest type of wave, but cause most damage due to a side - to side shearing motion

What are Rayleigh waves ?

these radiate from the epicentre in a complicated low frequency rolling motion

What is a moment magnitude scale ?

logarithmic scale used to measure the size of earthquakes based on their seismic moment, providing a more accurate representation of an earthquake's energy release than other scales like the Richter scale

What are some examples of primary earthquake hazards ?

• ground shaking

• surface rupture 

Why do some buildings collapse or not ?

• Resonance - during an earthquake building will vibrate to 1 particular frequency, when ground shakes to 1 particular frequency they’re in resonance amplifying affect of earthquake

• Pancake collapse - pillars and support fails building suddenly weakened - floors fall on top of each other like a stack of pancakes

• Soft geology - seismic waves travel faster through hard rocks than soft rocks and sediments, soft rocks amplify ground motion

• Liquefaction - process by which water saturated sediment temporarily loses strength and act as a fluid