Hazardous Earth SG6

Question 1

How long ago were the continents a single land mass called Pangaea?

Answer 1

200 million years ago

Question 2

How long ago did Pangaea split into two continents - Laurasia and Gondwanaland?

Answer 2

120 million years ago

Question 3

What is Alfred Wegener’s theory called?

Answer 3

Continental Drift

Question 4

When did Alfred Wegener publish his theory?

Answer 4

1915

Question 5

What four pieces of evidence did Alfred Wegener use for his theory?

Answer 5

Jigsaw fit of continents, Geological sequences (matching mountain belts), Glacial deposits, Fossil evidence

Question 6

What were the two fossils Wegener used as evidence?

Answer 6

Mesosaurus and Glossopteris

Question 7

Why were Alfred Wegener’s ideas dismissed?

Answer 7

Couldn’t understand how the continents could travel through the solid sea floor

Question 8

Define Echo Sounding

Answer 8

Send pulses of sound which travel to the sea floor and bounce back up again, The time it takes to come back up is how deep the sea floor is in that location

Question 9

What did Bruce Heezen and Marie Tharp discover from the echo sounding data?

Answer 9

Vast mountain chain running down the bottom of the ocean

Question 10

How long was the mountain chain found by Tharp and Heezen?

Answer 10

60,000km

Question 11

What did Tharp and Heezen notice about the crest of the mountain chain?

Answer 11

There was a cleft - a mid ocean ridge

Question 12

How did the mid ocean ridge found by Tharp support Wegener’s theory?

Answer 12

The ridge would be formed naturally if the continents were pulled apart

Question 13

Define Continental Drift

Answer 13

The theory that the continents are mobile and have moved across Earth’s surface through geological time

Question 14

Define Seismic Profiling

Answer 14

Dropping explosives off a ship and recording how long it takes for sound waves to return

Question 15

What was Harry Hess’ theory for continental drift?

Answer 15

Seafloor spreading

Question 16

Define Seafloor Spreading

Answer 16

Lateral movement of new oceanic crust away from a mid ocean ridge

Question 17

What evidence did Hess use for his idea of sea floor spreading?

Answer 17

The age of ocean floor basalt

Question 18

What data from the ocean floor did Vine use?

Answer 18

Magnetic reversals of polarity on the sea floor

Question 19

Define Core

Answer 19

The metallic centre of the earth, composed of mainly iron and nickel

Question 20

What state is the inner core?

Answer 20

Solid state (despite being more than 3,000 degrees)

Question 21

What state is the outre core?

Answer 21

Liquid state

Question 22

How thick is the mantle?

Answer 22

2,900km

Question 23

What is the mineral composition of the mantle?

Answer 23

Iron and magnesium rich

Question 24

What is the main rock type of the mantle?

Answer 24

Peridotite

Question 25

Define Crust

Answer 25

The outer layer of the earth which varies in characteristic depending on whether it is continental or oceanic

Question 26

What is the thickness of continental crust?

Answer 26

35km

Question 27

What is the thickness of oceanic crust?

Answer 27

5-70km

Question 28

What is the density of the mantle?

Answer 28

3.3g/cm3

Question 29

What is the composition of continental crust?

Answer 29

Granite

Question 30

What is the composition of the oceanic crust?

Answer 30

Basalt

Question 31

What is the density of the continental crust?

Answer 31

2.7g/cm3

Question 32

What is the density of the oceanic crust?

Answer 32

2.9g/cm3

Question 33

Define Asthenosphere

Answer 33

The semi-molten or viscous layer that extends from 100km to 300km deep

Question 34

Define Lithosphere

Answer 34

The rigid layer comprising of crust and the upper mantle above the asthenosphere

Question 35

Define Mohorovicic Discontinuity (Moho)

Answer 35

The boundary between the crust and the mantle

Question 36

How old is continental crust?

Answer 36

Up to 3.8 billion years old

Question 37

How old is oceanic crust?

Answer 37

Up to 220 million years old

Question 38

Define 1300 Degree Isotherm

Answer 38

The boundary between the lithosphere and asthenosphere

Question 39

Who developed the convection current theory?

Answer 39

Arthur Holmes

Question 40

What are the two sources of internal heat to generate convection currents in the mantle?

Answer 40

Heat remains from the formation of the Earth, Decay of radioactive elements - U, Th, K

Question 41

Define Ridge Push

Answer 41

Upwelling of magma at the mid ocean ridges creates new ocean crust causing the plates to push apart

Question 42

Define Plate Drag

Answer 42

Convection currents in the asthenosphere drag the overlying plate with it

Question 43

Define Trench Pull

Answer 43

The weight of the dense, cold oceanic crust subducting into the asthenosphere at an oceanic trench pulls down the rest of the plate with it

Question 44

Define Basaltic Magma

Answer 44

A type of magma which is low in silica and flows easily

Question 45

Define Decompressional Melting

Answer 45

A reduction in overlying pressure enables the peridotite to melt, leading to magma formation

Question 46

Define Fault

Answer 46

Cracks in rock due to stresses in the earth's crust

Question 47

What four features are associated with divergent plate boundaries?

Answer 47

Mid Ocean Ridges, Rift Valleys, Pillow Lavas, Black Smokers (Hydrothermal Vent)

Question 48

Define Mid Ocean Ridge

Answer 48

The boundary between two diverging plates consisting of two parallel chains of submarine mountains separated by a rift valley

Question 49

How are MORs formed?

Answer 49

As magma rises to the surface, the overlying rock thermally expands and is forces upwards into a dome

Question 50

What is the total length of a MOR?

Answer 50

60,000km

Question 51

What is the approximate height of a MOR?

Answer 51

300m

Question 52

What is the approximate width of a MOR?

Answer 52

1,000km

Question 53

What is the spreading rate of the Mid Atlantic Ridge?

Answer 53

2-3cm/year

Question 54

What is the spreading rate of the East Pacific Rise?

Answer 54

16.5cm/year

Question 55

What faults occur at MORs?

Answer 55

Transform faults

Question 56

Define Transform Fault

Answer 56

Large-scale faults in the crust at right angles to a mid ocean ridge, Earthquakes occur along their lengths as they slip

Question 57

Define Seamount

Answer 57

Submarine volcano

Question 58

Define Pillow Lava

Answer 58

Rounded mounds of lava erupted along mid-ocean ridges which cool rapidly on contact with sea water

Question 59

Define Black Smoker

Answer 59

Hydrothermal vent on the ocean floor, The water carries high amounts of metal sulphides

Question 60

Define Rift Valley

Answer 60

A valley formed by down faulting between parallel faults on MORs and at a divergent boundary on land

Question 61

What faulting occurs at rift valleys?

Answer 61

Normal faulting

Question 62

Define Normal Fault

Answer 62

A fault in which blocks of rocks slip straight down due to tension in the lithosphere

Question 63

Define Graben

Answer 63

The downfaulting section of a rift valley

Question 64

Where do grabens occur?

Answer 64

Rift valleys

Question 65

What % of the world's active volcanoes occur at convergent plate boundaries?

Answer 65

80%

Question 66

Define Andesitic and Rhyolitic Magma

Answer 66

Two types of magma which are high in silica and viscous (slow moving)

Question 67

What faulting occurs at convergent plate boundaries?

Answer 67

Reverse faults

Question 68

Define Reverse Faults

Answer 68

A fault in which one block of rock slides over another due to compression in the lithosphere

Question 69

What four features are associated with O/C convergent plate boundaries?

Answer 69

Earthquakes, Ocean Trenches, Fold Mountains, Volcanoes

Question 70

Define Ocean Trench

Answer 70

A narrow, deep depression on the ocean floor adjacent to a subduction zone

Question 71

How deep do ocean trenches go?

Answer 71

6,000 - 11,000m

Question 72

What are the dimensions of the Peru-Chile trench?

Answer 72

5900km long, 8km deep, 64km wide

Question 73

Define Benioff Zone

Answer 73

Boundary between a subducting ocean plate and the over-riding continental plate at a destructive boundary where earthquakes take place, Has an angle of 45 degrees

Question 74

Define Fold Mountains

Answer 74

A mountain built up by the crumpling (folding) of crustal rocks, Associated with convergent boundaries

Question 75

What four features are associated with O/O convergent plate boundaries?

Answer 75

Ocean Trench, Island Arc, Earthquakes, Volcanoes

Question 76

Define Island Arc

Answer 76

Chain of volcanic islands formed along a subduction zone

Question 77

What two features are associated with C/C convergent plate boundaries?

Answer 77

Fold Mountains, Earthquakes

Question 78

Define Tectonic Plate

Answer 78

A large slab of the Earth's lithosphere and crust

Question 79

Define Subduction

Answer 79

The tectonic process found at destructive plate margins where an oceanic plate descends into the Earth's mantle and is destroyed

Question 80

Define Divergent Boundary

Answer 80

Two tectonic plates move away from each other

Question 81

Define Conservative Boundary

Answer 81

Two tectonic plates slide past each other

Question 82

Define Convergent Boundary

Answer 82

Two tectonic plates move towards each other