Plate Tectonics

Question 1

What did Alfred wegner propose?

Answer 1

Single continent Pangea

Continental drift

Question 2

Explain geological evidence for continental drift

Answer 2

South America and west Africa shape fits

Carboniferous glaciation deposits in South America Antarctica and India

Striations on rocks in west Africa and Brazil

Question 3

Explain biological evidence for continental drift

Answer 3

Fossil brachiopods found in Indian limestone and Australia

Fossil remains of a reptile in southern America and South Africa - unlikely it could have migrated across the Atlantic not suited to swim

Question 4

What is the idea of paleomagnitism and sea floor spreading?

Answer 4

Rocks near ridge are younger than away
Alternating polarity of rocks is mirrored of magnetic stripes

When volcanos erupt lava solifked and particles left behind

Question 5

What is ridge push? What’s this also known as?

Answer 5

At constructive plate, diverging plate is more buoyant
Ocean ridge can rise up to 3 m
In opposition, gravity pulls plate down and away

Gravitational sliding

Question 6

What is slab pull?

Answer 6

Cooler denser oceanic plate is pulled to the mantle

Gravity pulls it down

Question 7

What is the destructive collision? And name an example

Answer 7

When plates collide and one is destructed

Indian and Eurasian

Question 8

What is the destructive subduction?

Answer 8

Oceanic plate forced under continental plate and is destroyed

Nazca plate subduction South America plate

Question 9

What is the conservative plate boundary?

Answer 9

When plates slide next to each other

San Andreas fault

Pacific and north American plate

Question 10

What is the constructive plate boundary?

Answer 10

Plate pull apart to make ridge

North America and Eurasian

Question 11

What is the core made from?

Answer 11

Dense rocks containing nickel and iron alloys

Question 12

What is the inner core?

Answer 12

Solid

Question 13

What is the outer core?

Answer 13

Molten / liquid

Question 14

What is the temperature of the core?

Answer 14

More than 5000

Question 15

What is the heat energy from the core? (2) and what do they mean

Answer 15

Primordial left over from earth formation

Radiogenic by radioactive decay of isotopes

Question 16

What is the mantel made from

Answer 16

Molten and semi molten rocks

Question 17

What is the temperatures of the mantle

Answer 17

4000 near core

1000 near crust

Question 18

What is the lithosphere? And the characteristics (3)

Answer 18

Crust and upper mantle
80-90km thick
Divided into 7 large plates and lots of smaller ones

Question 19

What is the asthenosphere and what do plates do here

Answer 19

Semi molten rock below lithosphere

Plates float and move

Question 20

What is the difference between continental and oceanic crust?

Answer 20

Continental is thicker and less dense than oceanic

And much older

Question 21

What is an ocean ridge and what plate boundary is it found at

Answer 21

Underwater mountain system
Formed when plates move apart
Constructive

Question 22

What is a Rift Valley and what plate boundary is it found at?

Answer 22

Plates love apart and land drops to form deep trench called a graven and land either side is called a graben
Constructive

Question 23

What is a shield volcano and what plate boundary is it found at?

Answer 23

Flat sides volcano, runny lava, gentle eruptions

Constructive

Question 24

What is an ocean trench and what plate boundary is it found at?

Answer 24

Occurs through subduction
Oceanic plate forms a trench as it subducts

Destructive

Question 25

What is island arcs and what plate boundary is it found at?

Answer 25

Oceanic plate melts when it subducts and begins to rise to surface Forms composite volcano If it erupts off shore volcanic islands are formed Chain of volcanos arc shaped Destructive

Question 26

What is a young fold mountainand what plate boundary is it found at?

Answer 26

Plates forced together Edges and sediments are forced into fold. Mountains The Effects of folding layers within upper crust Destructive

Question 27

Explain the concept of hotspots

Answer 27

Radioactive decay in the inner core becomes concentrated Creates localised thermal currents when plumes rise vertically and burns the crust The plume is stationary but the plate moves ( e.g. In Hawaii the Pacific plate moves)