tectonics EQ1

Question 1

1.1 where does most tectonic activity occur?

Answer 1

along plate boundaries, especially around the ring of fire (circum pacific belt). 95% of all earthquakes occur along plate boundaries.

Question 2

1.1 describe a divergent boundary

Answer 2

two plates diverge, forming new crust. Mid ocean ridges extend underwater as mountain chains with transform faults cutting across them.

Question 3

1.1 what seismic activity occurs at a divergent plate boundary?

Answer 3

• mild shallow-focus earthquakes
• volcanic eruptions

Question 4

1.1 describe a convergent plate boundary (oceanic v continental)

Answer 4

oceanic v continental: denser oceanic crust subducts beneath continental crust into the upper mantle and melts. marked by DEEP OCEAN TRENCHES. Subduction leads to FOLD MOUNTAINS. Results in major earthquakes and explosive volcanic eruptions

Question 5

1.1 describe a convergent plate boundary (oceanic v oceanic)

Answer 5

subduction of the lighter plate occurs. DEEP OCEAN TRENCHES and VOLCANOES form. submarine volcanos form ISLAND ARCS. Causes shallow to deep focus earthquakes.

Question 6

1.1 describe a collision plate boundary?

Answer 6

two continental plates converge towards eachother. Rock is forced up to form high FOLD MOUNTAINS like the Himalayas. No volcanic activity, shallow focus earthquakes.

Question 7

1.1 describe a conservative plate boundary?

Answer 7

when two plates slide past each other at different speeds or in different directions. No volcanic activity, this movement causes powerful shallow focus earthquakes.

Question 8

1.1 What is an intra-plate earthquake?

Answer 8

Earthquakes that occur in the middle of plates. Their cause is uncertain but is most likely stresses from ancient faults reactivating. Distribution is random so prediction is more difficult.

Question 9

1.1 What are Hot Spot Volcanos?

Answer 9

Not located along plate margins. Unusually hot regions of the mantle rise in magma plumes then erupt on the ocean floor forming a volcano. As a plate moves over the hotspot, the volcano is carrier along with it, and a new volcano replaces it forming a chain of volcanic islands

Question 10

1.2 What is plate tectonic theory?

Answer 10

A theory that states the earth’s lithosphere is broken into large, rigid pieces called tectonic plates that can move relative to each other by sliding on the asthenosphere.

Question 11

1.2 According to plate tectonic theory, how are plates though to move?

Answer 11

convection, gravity, slab pull , sea floor spreading, subduction, ridge push

Question 12

1.2 How do plates move by mantle convection?

Answer 12

Geothermal energy caused by radioactive decay in the core heats up the mantle producing convection currents as the heat rises, when the heat travels parallel to the crust, it moves the plate in the direction of travel, less widely accepted.

Question 13

1.2 How do plates move by seafloor spreading?

Answer 13

Mid-ocean ridges form when hot magma is forced up through the asthenosphere and hardens forming new oceanic crust. This spreading pushes the tectonic plates apart

Question 14

1.2 What is paleomagnetism?

Answer 14

A record of changes in the Earth’s magnetic fields, when lava solidifies, minerals line up with the Earth’s magnetic direction. Mid ocean ridges show patterns of magnetic direction mirrored on each side of the ridge.

Question 15

1.2 How does subduction move tectonic plates?

Answer 15

as two plates move towards each other one slides under the other at a 45 degree angle into the subduction zone

Question 16

1.2 How do tectonic plates move by slab pull?

Answer 16

newly formed oceanic material at mid ocean ridges becomes denser and thicker as it cools, causing it to sink into the mantle, pulling the rest of the plate down with it

Question 17

1.2 How are tectonic plates moved by ridge push?

Answer 17

Rising mantle material forces plates to move apart at mid ocean ridges

Question 18

1.2 outline the earth’s internal structure

Answer 18

INNER CORE: solid, iron and nickel, 6000 degrees
OUTER CORE: liquid, iron and nickel, 4500-6000 degrees
LOWER MANTLE: semi- molten
ASTHENOSPHERE: solid
LITHOSPHERE: oceanic and continental crust
OCEANIC: younger, thinner, 6-10km, denser
CONTINENTAL: older, thicker, 45-50km, less dense

Question 19

1.2 What processes of tectonic movement occur at a divergent boundary?

Answer 19

• sea floor spreading
• slab pull
• convection currents
• ridge push

Question 20

1.2 What processes of tectonic movement occur at a convergent boundary?

Answer 20

• Subduction
• convection currents
• ridge push

Question 21

1.2 What tectonic movements occur at a collision boundary?

Answer 21

• ridge push
• convection currents

Question 22

1.2 What tectonic movements operate at conservative margins?

Answer 22

• convection currents

Question 23

1.3 describe Pressure waves

Answer 23

• fastest seismic wave to reach surface
• through solids and liquids
• oscillate back and forth
• longitudinal
• least damaging

Question 24

1.3 Describe Shear waves

Answer 24

• slower
• only through solids
• sideways oscillation
• transverse

Question 25

1.3 describe Love waves

Answer 25

• slowest
• most damaging
• ground shakes side to side
• larger
• focus all energy on ground
• transverse

Question 26

1.3 what are some primary impacts of earthquake waves?

Answer 26

• crustal fracturing: large breaks or faults in the lithosphere
• ground shaking: ground moves due to P S or L waves

Question 27

1.3 Liquefaction example of secondary hazard

Answer 27

2011 Christchurch NZ
surface rocks lose strength and act more like a liquid than a solid. Subsoil loses ability to support foundations, buildings and roads tilt or sink. 185 died, 90% of buildings in CBD damaged.

Question 28

1.3 tsunami example secondary hazard

Answer 28

2004 Indian Ocean tsunami
a series of waves due to underwater earthquake that lead to water column displacement. destroyed ecosystems like coral reefs, destroys economies like Thailand’s tourism industry which lost $25 million each month. 300,000 died.

Question 29

1.3 landslide example secondary hazard

Answer 29

2015 Ghorka Nepal
ground shaking places stress on slopes so they fail. 9000 died, 800,000 buildings damaged, village buried, agricultural land destroyed

Question 30

1.3 name primary hazards of volcanic eruptions

Answer 30

• lahars
• pyroclastic flows
• ash/tephra falls
• gas eruptions

Question 31

1.3 name secondary hazards of volcanic eruptions

Answer 31

• jokulhlaup
• lahars

Question 32

1.3 what are lava flows

Answer 32

streams of lava that have erupted, up to 1170 degrees. Often not a threat to life due to slow pace, however destroy everything in their path

Question 33

1.3 What are pyroclastic flows

Answer 33

\fast moving, destructive mix of hot rock, lava, ash, and gases ejected from the volcano, move quicker at 100km/h up to 700 degrees.

Question 34

1.3 What are ash/tephra falls?

Answer 34

Tephra are pieces of volcanic rock and ash blasted into the air, they cause injury or death, covers everything and threatens to clog engines

Question 35

1.3 What are gas eruptions?

Answer 35

Magma contains dissolved gases that are released into the atmosphere including water vapour, carbon dioxide, sulphur dioxide

Question 36

1.3 What are lahars?

Answer 36

flows of mud, rock, and water down the volcanic slopes, can be hundreds of meters wide and are too fast to outrun. Form when eruptions melt snow and ice or when heavy rainfall during an eruption erodes loose rock and soil

Question 37

1.3 What are jokulhlaups?

Answer 37

Glacial outburst floods when heat from an eruption melts the ice and snow resulting in sudden releases of water, rock, gravel, ice. Very dangerous to infrastructure and life.

Question 38

1.3 Name some positive impacts of the Eyjafjallajokull eruption in 2010

Answer 38

• Ash warmed and added nutrients into the soil
• Tourism enhanced
• No victims

Question 39

1.3 Name some negative impacts of the 2010 Eyjafjallajokull eruption?

Answer 39

• Flights cancelled due to clogged engines
• Airlines lost US$1.7B
• Floods/jokulhlaups
• Ash (230million m^3)
• Tephra
• Roads destroyed

Question 40

1.3 What was the VEI of the 2010 Eyjafjallajokull eruption

Answer 40

3.5 on a scale of 1-8

Question 41

1.3 what 4 things can cause a tsunami

Answer 41

asteroids
earthquakes
volcanic eruptions
landslides

Question 42

1.3 how do tsunamis occur as a result of earthquakes?
what are tsunami waves like?

Answer 42

the energy released forces the sea floor to lift, displacing the water column above, forming tsunami waves. Tsunami waves do not crest or break. Tall, fast-moving tsunami waves can destroy everything in their path and drag it back out to sea. The water can travel several miles inland, destroying buildings, farmland, trees, houses, bridges, soil, foundations etc.

Question 43

1.3 how do tsunamis cause death?

Answer 43

via drowning or collapsing buildings. Additionally tsunamis contaminate food and water, leading to the spread of water borne diseases like cholera.

Question 44

1.3 How are tsunamis predicted?

Answer 44

• early warning systems in the pacific and Indian oceans.
• Seismic sensors detect undersea earthquakes.
• DART stations (deep-ocean assessment and reporting of tsunami) stations use sensors and buoys to monitor changes in sea level that indicate water displacement.
  This can estimate size and direction of the tsunami once it has been triggered.

Question 45

1.3 What was the magnitude of the 2004 Indian ocean tsunami’s earthquake?

Answer 45

9.0-9.3

Question 46

1.3 what was the ocean floor upthrust in Indian ocean tsunami?
how tall were the waves?

Answer 46

15 meters
17 meters

Question 47

1.3 How many people died due to the Indian ocean tsunami in 2004?

Answer 47

230,000

Question 48

1.3 how many people were made homeless by the 2004 indian ocean tsunami?

Answer 48

1,700,000

Question 49

1.3 2004 indian ocean tsunami effect on economy?

Answer 49

• Thailand tourism industry lost US$25 million each month
• 120,000 jobs lost
• US$13 billion +

Question 50

1.3 2004 Indian ocean tsunami effects on environment?

Answer 50

• mangroves and coral reef ecosystems destroyed
• water and soil contaminated by salt water