Chapter 12.2 Features of Plate Tectonics

Question 1

what is the top layer of the earth called?

Answer 1

The crust, which is made out of elements of oxygen, silicon which form to make groups of rocks called silicates

Question 2

What are the 5 layers of the earth called? (order from exterior to interior)

Answer 2

crust, upper mantle, lower mantle, outer core, inner core

Question 3

what does the lithosphere include?

Answer 3

crust, uppermost mantle, tectonic plates

65 - 100 km thick

Question 4

what is the asthenosphere?

Answer 4

below lithosphere, partially liquid in upper mantle

temp varies because of large quantities of radioactive elements such as uranium in some areas

Question 5

explain mantle convection

Answer 5

radioactive decay heats up mantle
heated particles have more kinetic energy, move around more, spreading farther apart
convection current in the asthenosphere happens when the hotter, less dense material rises, cools, then sinks again, the cycle starts over

Question 6

what happens if a spreading centre occurs in the ocean?

Answer 6

it will create an oceanic ridge or a trench

Question 7

what happens if a spreading centre occurs on land?

Answer 7

it will create a rift valley

Question 8

what is ridge push?

Answer 8

when new material arises from the asthenosphere and pushes older material aside, tectonic plates move away from the ridge

Question 9

what is subduction?

Answer 9

the action of one plate pushing below another

a dense oceanic plate sub-ducting under a less dense continental plate

Question 10

what are subduction zones?

Answer 10

areas of subduction that experience large earthquakes and volcanic eruptions

Question 11

what is slab pull?

Answer 11

when a tectonic plate subducts deep into the mantle, pulling the rest of the plate with it

Question 12

what is a plate boundary?

Answer 12

a region where 2 tectonic plates are in contact

Question 13

what are the 3 types of plate interaction?

Answer 13

divergence (spreading apart), convergence (moving together) and transform (sliding by)
depends on the type of plate and direction the plates are moving

Question 14

what are divergent plate boundaries?

Answer 14

areas where tectonic plated are spreading apart

Question 15

what are diverging plates? give an example

Answer 15

plates that are spreading apart

the mid atlantic ridge spreading ridges that separate, americas from africa, europe and asia

Question 16

what is a converging plate boundary?

Answer 16

where tectonic plates collide

Question 17

what are converging plates?

Answer 17

plates that collide

Question 18

what happens during ocean-continental plate convergence?

Answer 18

oceanic plate subducts under continental plate, creates a deep underwater valley called a trench
subducting plate melts as it goes deeper, cools and crystallizes into large rock masses below continental plate surface
could make cone shapes volcanoes if the magma works itself up to the surface (ex. Juan de fuca plate (oceanic) and north american plate (continental) has a long chain of volcanoes
the force of collision between the oceanic/continental plate could create mountain ranges due to the folding and crumpling of the continental plate (ex. BC’s coast mountains)
earthquake results in pressure building up due to the resistance in convection currents, ridge push and slab pull and releases pressure

Question 19

what happens during oceanic-oceanic plate convergence?

Answer 19

when a denser oceanic plate subducts under a less dense oceanic plate
may produce a long chain of volcanic islands called a volcanic island arc
ex. islands of japan and indonesia

Question 20

what happens during continental-continental plate convergence?

Answer 20

subduction does not occur because plates’ similar densities prevents one from going under the other
creates massive mountain ranges
ex. Himalayas

Question 21

what are transform plate boundaries?

Answer 21

when convection currents in the mantle cause tectonic plates to slide past each other

Question 22

what are faults?

Answer 22

breaks in rock layers due to movement on either side

Question 23

what is a transform fault?

Answer 23

a fault that occurs at a transform plate boundary

ex. Andreas fault of california in us

Question 24

What is an earthquake?

Answer 24

when tectonic plates release energy from pressure building up

Question 25

Where is the focus point located?

Answer 25

Where slippage of the plates take place inside the earth

Question 26

what is the point above the focus point called?

Answer 26

epicenter

Question 27

What are seismic waves and what are the different types?

Answer 27

the shaking in an earthquake, P waves (primary wave fastest speed, ground squeezes/stretches in direction of wave travel), S waves (secondary wave second fastest, cannot travel through liquids) and L waves (surface wave, travels along earths surface, makes ground ripple)

Question 28

How did we discover the composite layers of the earth?

Answer 28

change in speed and direction of the seismic waves (p wave travels all the way through but changes direction slightly, s waves are not found on other side of earth)

Question 29

how do we measure earthquakes?

Answer 29

through how much shaking is taking place or seismometres/seismographs

Question 30

what’s a seismogram?

Answer 30

physical records of ground motion

Question 31

what is the richter scale?

Answer 31

measures earthquakes and how much shaking is taken place
uses magnitude, is a logarithmic scale
so, difference between magnitude 3 and 5 is 10x10=100

Question 32

What are the 3 types of volcanoes?

Answer 32

Composite, shield and rift eruptions

Question 33

How are composite volcanoes made?

Answer 33

When layer after layer of ash and thick lava build up/cool
they erupt when thick lava traps gas underneath it, pressure rises and explodes
found in volcanic belts
ex. composite volcanoes in canada are eroded so they dont have the classic cone shape
tallest in size

Question 34

How are shield volcanoes made?

Answer 34

When layer after layer of thin magma builds up and cools down (b/c the gas does not get trapped as much, less pressure, smaller explosions)
magma flows more freely, spreading it out, creating a larger area
looks like shield on ground when looking from above
form in areas of thin lithospheres (hotspots)
ex. Hawaiian Island chain

Question 35

What are rift eruption?

Answer 35

usually occur where there is plate divergence, in an ocean ridge or rift valley
a subsection of shield volcanoes
has a lot of surface area, smaller explosions but releases enormous amounts of lava
ex. mid atlantic ridge