Tectonic Plates

Question 1

What layers does the earth consist of?

Answer 1

Continental crust, oceanic crust, mantle, outer core, inner core.

Question 2

What are the properties of the continential crust?

Answer 2

10-70km thick, rich in silicates and aluminium minerals

Question 3

What are the properties of the oceanic crust?

Answer 3

5km think, more dense with composition similar to basalt

Rich in magnesium and silicate minerals

Question 4

What are some properties of the mantle?

Answer 4

Thickest layer of the earth, molten rock with convection currents in the upper mantle, high tempreture and pressure

Question 5

What are some properties of the outer core?

Answer 5

Liquid, contains Fe, Ni and some lighter elements, convection currents in the outer core may be responsible for the earths magnetic field

Question 6

What are some properties of the inner core?

Answer 6

Solid, made mostly of Fe with some Ni

Question 7

What is the total depth of the crust?

Answer 7

0-100km

Question 8

What is the total depth of the mantle?

Answer 8

100-2900km deep

Question 9

What is the total depth of the outer core?

Answer 9

2900-5100km deep

Question 10

What is the total depth of the inner core?

Answer 10

5100-6378km deep

Question 11

What happens when a seismic wave passes from a slower velocity layer to a higher velocity layer?

Answer 11

The seismic wave is refracted up

Question 12

What happens when a seismic wave passes from a higher velocity layer to a slower velocity layer?

Answer 12

The seismic wave is refracted down

Question 13

What can the reflection of seismic waves be used for?

Answer 13

It can be used to determine the depth of a layer within the earth

Question 14

What was the shrinking theory?

Answer 14

The shrinking theory rose in the 1800s when geologists believed that due to the crust cooling down it formed continents valleys and mountains and when it cooled the heaver metals sunk to the core while less dense materials stayed or rose the surface.

Question 15

What does continental drift mean?

Answer 15

It means that millions of years ago all the continents made one large super continent which eventually broke up leaving singlular continents.

Question 16

Who proposed the continental drift theory?

Answer 16

In 1912, a German meteorologist named Alfred Wegener proposed a new theory.
He had noticed that the present day continents looked as though they would fit together very much like a jigsaw puzzle.

Question 17

What did Alfred Wegener propose?

Answer 17

Wegener suggested that the continents were floating, or drifting, on a denser material underneath.
He proposed that the continents were breaking apart and rejoining in a process that he called continental drift.

Question 18

What was Pangea?

Answer 18

Pangea was surrounded by a global ocean called Panthalassa, and it was fully assembled 299 million to 272 million years ago
The supercontinent began to break apart about 200 million years ago
Eventually forming the modern continents and the Atlantic and Indian Oceans

Question 19

What was Laurasia?

Answer 19

Laurasia,ancient continental mass in the Northern Hemisphere that included North America, Europe, and Asia (except peninsular India)
Wegener had postulated a single supercontinent, Pangea
Du Toit, another scientist, theorised that there were two landmasses: Laurasia in the north and Gondwana in the south, separated by an oceanic area called Tethys

Question 20

What was Gondwana?

Answer 20

Gondwana, ancient supercontinent that incorporated present-day South America, Africa, Arabia, Madagascar, India, Australia, and Antarctica
The first stage of its breakup began about 180 million years ago
Alfred Wegener, envisioned a single great landmass, Gondwana comprised the southern half of his supercontinent

Question 21

What was the evidence for the continental drift?

Answer 21

The same fossils of plants and animals could be found on different continents
Mountains were formed when the edge of a drifting continent collided with another, causing it to crumple and fold

Question 22

What is the atmosphere?

Answer 22

A blanket of gases that surrounds the Earth to a height of approximately 145km. Mostly made up of nitrogen and oxygen, which support life on earth.

Question 23

What is the tempreture of the mantle? (celcius)

Answer 23

500-2000

Question 24

What is the tempreture of the outer core?

Answer 24

4000-6000

Question 25

What is the hydroshpere?

Answer 25

The water on or at the surface of the Earth including oceans, lakes, rivers, rain and mist.

Question 26

What is the tempreture of the inner core?

Answer 26

up to 7000

Question 27

What is the evidence for plate tectonics?

Answer 27

Mapping of the ocean floor revealed the presence of mid-ocean ridges
Mid-ocean ridges are undersea volcanic mountain ranges
New seafloor is formed at these ridges in a process known as seafloor spreading
Molten rock from inside the Earth rises into the gap and cools and solidifies into new rock
As it solidifies a record of the Earth’s magnetic field is locked into the new rock
As you move further away from the ridge the age of the rock increases
Magnetic particles in molten rock align with Earth’s magnetic field
Magnetic record is stored within the rocks when they cool and solidify
The pattern of reversed polarity repeats on either side of mid-ocean ridges

Question 28

What are convetion currents and how do they work?

Answer 28

Hot metallic core causes the mantle directly above it to heat up
As the liquid rock in the mantle heats up it rises
When it reaches the top of the mantle it gets pushed aside by more mantle rising below it
As the hot liquid spreads out it cools and sicks to the bottom of the mantle layer
It is reheated by the core and the cycle of heating and cooling begins again

Question 29

What are convection shells?

Answer 29

The closed system of the mantle results in ‘convection cells’
Local regions of liquid or gas that form a relatively stable cycle of heating, rising, moving aside, cooling and sinking

Question 30

What are tectonic plates?

Answer 30

Earth composed of many plates which are in constant motion due to the convection currents beneath them
Plate boundaries have been identified by mapping zones of earthquake and volcanic activity along with mid ocean ridges

Question 31

What is a Divergent and its properties?

Answer 31

plates pull apart, creates a ridge/rift, allows volcanic activity and creates oceanic lithiosphere.

Question 32

What is a Convergent and its properties?

Answer 32

Its the collision of plates, subducts, destroys oceanic lithiospheres creats trenches and allows for volcanic activity.

Question 33

What is a Transform?

Answer 33

Plates grind past each other, lateral sliding, a lithiosphere is not created or destroyed, no major effect on land, and doesnt allow for volcanic activity.

Question 34

Extra information on Divergent boundaries (don’t recall but still good to know for exam)

Answer 34

Mid-ocean ridges, Iceland, African rift Valley
Produce few earthquakes because plates pulling apart
Not storing up energy as they collide or rub past each other
Plates moving apart forming a gap where magma is pushed up from the mantle below
Lots of volcanoes, thermal vents and great broken rifts in the Earth occur at divergent boundaries

Question 35

Extra information on Convergent boundaries (don’t recall but still good to know for exam)

Answer 35

Subducting convergent boundaries can be found along the north-western edges of the Pacific Plate, the west coast of South America and the north-eastern edges of the Indo-Australian Plate
Produce a combination of volcanoes and earthquakes
A lighter plate floats on top while another plate dives below – subduction
Submerging plate melts and the resulting magma bubbles up through cracks in the overlaying crust to form volcanoes
Continent-to-continent convergent boundaries, such as Himalayas
Produce lots of earthquakes but very little volcanic activity
Continental crust on both sides is light and resists subduction
Continents buckle and crumble against one another, gradually rising skywards

Question 36

Extra information on Transform boundaries (don’t recall but still good to know for exam)

Answer 36

San Andreas fault on land, most others lie on the ocean floor
Produce lots of earthquakes and only occasional volcanic activity
Plates moving past one another
Store energy between them until the friction holding them together gives way in the form of an earthquake

Question 37

What is a hotspot?

Answer 37

Volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle
They may be on, near to, or far from tectonic plate boundaries.
Well known examples include Hawaii and Yellowstone