The structure of the earth

Question 1

what is on the outside layer of our earth?

Answer 1

a rocky crust

Question 2

what is the outer layer of the earth made from?

Answer 2

tectonic plates

Question 3

how fast do tectonic plates move?

Answer 3

very slowly

Question 4

where are tectonic plates found?

Answer 4

on the outer layer of our earth

Question 5

what does the movement of tectonic plates cause?

Answer 5

earthquakes and volcanoes at the plate boundaries`

Question 6

how long has it took continents to move apart?

Answer 6

millions of years

Question 7

what is the outer layer of the earth called?

Answer 7

the lithosphere

Question 8

what makes up the lithosphere?

Answer 8

the crust and part of the mantle

Question 9

explain what the lithosphere is?

Answer 9

relatively cold and rigid

Question 10

finish this sentence… The tectonic plates that make up the earth’s crust is less dense than what

Answer 10

the rest of the mantle below

Question 11

why has the theory of plate tectonics been accepted?

Answer 11

it explains the evidence. It has been tested and the results discussed by many scientists

Question 12

can we drill through the crust?

Answer 12

no

Question 13

how do we judge the thickness of layers in our earth?

Answer 13

by the use of seismic waves produced by earthquakes and by artificial explosions

Question 14

explain what the lithosphere is?

Answer 14

rigid and brittle

Question 15

what is the lithosphere divided into?

Answer 15

tectonic plates

Question 16

what is the semi-rigid layer called?

Answer 16

the asthenosphere

Question 17

explain the asthenosphere

Answer 17

it is hotter and like plasticine, which can flow even though its a solid

Question 18

how is energy through the earth’s core transferred towards the surface?

Answer 18

by convection currents in the mantle. These convection currents slowly move the plates

Question 19

what directions can tectonic plates move?

Answer 19

apart, collide, scrape past eachother

Question 20

which is more dense continental or oceanic?

Answer 20

oceanic

Question 21

what are the two types of plates?

Answer 21

continental and oceanic

Question 22

where can we find continental and oceanic plates?

Answer 22

oceanic accumulate on top where oceanic plates float higher in the mantle

Question 23

what is subduction?

Answer 23

where the oceanic plate sub ducts under the continental

Question 24

what causes an earthquake?

Answer 24

when the sinking plate descends, it may get stuck and then suddenly move

Question 25

what happens further down?

Answer 25

it partially melts to form magma

Question 26

how are volcanoes formed?

Answer 26

magma working its way up to the surface creating a chain of valcanoes on the edge of the plate

Question 27

How is igneous rock formed?

Answer 27

when magma cools and solidifies

Question 28

how are small crystals formed in igneous rock?

Answer 28

when it cools rapidly close to the surface

Question 29

how are large crystals formed in igneous rock?

Answer 29

when it cools slowly further from the surface

Question 30

what is lava

Answer 30

molten rock that reaches the surface of the earth from volcanoes

Question 31

how can you tell a safe volcano form an unsafe volcano?

Answer 31

if the lava is runny it is safe. If it is thick and sticky then an eruption can be explosive

Question 32

why do some people live near volcanoes?

Answer 32

because the ash makes a rich soil that is good for growing things

Question 33

why does magma rise through the earth's crust?

Answer 33

because it is less dense than the crust

Question 34

what was the theory called that meant all continents wear joined at one point

Answer 34

the continental drift theory

Question 35

who suggested this theory?

Answer 35

Alfred wegner

Question 36

why was his theory not accepted?

Answer 36

no one could explain how the continents were able to move through the rocks of the ocean floor

Question 37

why was his theory accepted later?

Answer 37

because geologists found a huge ridge in the middle of the Atlantic ocean

Question 38

what does this prove?

Answer 38

that the sea floor is spreading outwards at this point. This is where plates are being formed

Question 39

what are subduction zones?

Answer 39

where plates are being destroyed

Question 40

explain iron-rich magma?

Answer 40

tends to be runny so if it spills people can get away (safe)

Question 41

explain silicia- rich magma?

Answer 41

forms rhyolite if it cools rapidly and is less runny

Question 42

what causes explosive volcanoes?

Answer 42

when dissolved gases in the magma have no time to escape the stiff liquid. The magma erupts like spray. It shoots out as clouds of searingly hot ash and pumice