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Question 1

Natural hazards

Answer 1

-a naturally occurring event that threatens human lives, cause damage to property

Question 2

Internal sturcuture of earth: Crust

Answer 2

• outermost
• made up of basalt and granite
• thickness: few km, up to 70-100km for some parts
• general temp: increases with depth towards the mantle between 200-400 degrees (hotter nearer to mantle)

Question 3

Internal structure of earth: Mantle

Answer 3

• mostly solid rock (semi-molten state) that flows just beneath the crust
• general thickness: 2900km
• general temperature: 800-3000 degrees

Question 4

Internal structure of earth: Core

Answer 4

• innermost
• mostly made out of iron and nickel
• general thickness: 3300km
• general temp: 3000-5000 degrees

Question 5

5 facts abt the external structure of earth

Answer 5

• external structure changed over the years
• tectonic plates are always moving due to convection current
• the crust is broken into large pieces known as tectonic plates
• tectonic plates made up of either continental crust/ oceanic crust/ both
• tectonic plates are always moving

Question 6

Fact 1: External structure has changed over the years

Answer 6

• Alfred Wegener’s Theory in 1915
• studied fossil remains of land creatures and plants
• fitting continental coastlines
• matching fossil reptiles in Africa and South America
• rocks are of same age and geological structures
• presence of coal (fossil fuels, require a lot of lifeforms in past for coal to be formed) under Antarctic ice cap

Question 7

Fact 2: Tectonic plates are always moving due to convection current

Answer 7

• convection currents are movements of heat within the mantle
• material in mantle is heated by core, causes mantle materials (magma) to expand, rise and spread out beneath the plates, causing them to be dragged along and move away from each other
• hot mantle material (magma) cools slightly and sinks, pulling the plates along, plates brought towards each other
• constant rising and cooling results in occurrence of convection currents which causes tectonic plates to move every year
• slab pull force: occurs when dense, sinking oceanic plate at subduction zones pulls rest of plate behind it, currently thought to be the main driving mechanism for plate movement

Question 8

Fact 3: crust is broken into large pieces known as tectonic plates

Answer 8

-refer to map and memorize

Question 9

Fact 4: Tectonic plates are made up of either continental crust or oceanic crust or both

Answer 9

• things to look out for between the two:
  1. location
  2. age of rock
  3. type of rock
  4. thickness

Question 10

Continental crust

Answer 10

Location: found between earth’s continental land masses and under shallow seas close to continents
Age of rock: a wide range (from recent to 4 billion yrs old)
Type of rock: mainly lighter rocks, including granite
Thickness: between 30-70km (some parts up to 100km)

Question 11

Oceanic crust

Answer 11

Location: found beneath deep oceans
Age of rock: Newer/younger rocks (less than 200 mil yrs old)
Type: mainly basalt, a heavy and dense rock
Thickness: between 5-8km

Question 12

Fact 5: Tectonic plates always moving

Answer 12

Divergent: plates move away from each other
Convergent: plates move towards each other
Conservative/transform: plates moves slide past each other