Edexcel Geography Unit 1 Revision Notes

Geography Unit 1 Revision

RESTLESS EARTH:

 

Layers of the Earth:

Crust- made from thin layers of tectonic plates

-          Continental crusts- granitic- thicker 25-80km

-          Oceanic crust- basaltic- denser 6-8km

Mantle- divided into solid upper part and semi-liquid lower part, which can flow

Core- liquid outer core and solid inner core 

 

Convection currents and plate movement

1.       The core heats the molten rock to create a convection current

2.       Heated rock from the mantle rises to earth’s surface

3.       At the surface the convection current moves the tectonic plates in the crust

4.        Molten rock cools and flows back to core to be reheated

 

Plate boundaries:

1.       Destructive- Nazca plate and South American plate

-          Two plates collide and subduction occurs

-          Many earthquakes and volcanoes

2.       Constructive - Eurasian and North American Plate

-          Convection current pull plates apart forming volcanic ridges e.g. mid- Atlantic ridge

3.       Conservative - San Andreas Fault, California

-          Two plates slide pass each other

-          Earthquakes occur

4.       Collision- Indo-Australian and Eurasian plates

-          Two continental plates collide and the two plates buckle

-          Earthquakes and fold mountains e.g. Himalayas or Andes

 

 

Kashmir, 2005

Loma Prieta, CA, 1989

Dead

75 000

63

Injured

75 000

3757

Homeless

2.8 million

12 000 homeless

Property cost

440 million

10 billion

Where

Remote mountainous area

Built up, accessible area

Richter Scale

7.6

6.9

 

Primary impacts- the immediate effects of an earthquake on property and people- shaking and property destruction, volcano- impact of lava flow/ pyroclastic flow on property

Secondary impacts- impact on property and people after event has finished- lack of shelter and basic supplies as well as fires and cholera

-          Disruption on infrastructure

-          Disruption to employment and travel

-          Decline of agricultural outputs due to pyroclastic flows

-          Cholera outbreak- disrupted sewage system

 

Shield volcano (Mauna Loa) –Hawaii

-          Found at constructive plate boundaries

-          Eruptions are frequent but gentle

-          Thin runny lava- flows long way before it solidifies

-          Low with gentle sloping sides

-          Basaltic magma with low silica and gas content

Composite volcano (Monserrat) – Caribbean

-          Destructive plate boundaries

-          Eruptions of viscous, sticky lava and ash that doesn’t flow far

-          Steep sloping sides and narrow base

-          Layers if thick lava and ash

-          Andesitic magma but high silica and gas content

-          Erupts infrequently but violently, pyroclastic flows(mix of ash, gases and rock)

 

Montserrat 1995 (composite volcano) – 19 killed

-          2/3 of town covered in ash- 50% of population evacuated to north

-          Eruption sent out large amounts of ash and lava and pyroclastic flow

-          6500 out of 10000 left island economic impacts- settlements abandoned- large scale migration

-          Tourism is suffering with few vissitors

…