Mountains Lecture 1- Moving plates, building mountains: the basics of plate tectonics

Question 1

Are mountains vulnerable to climate change?

Answer 1

Yes

Question 2

What are 6 reasons why we should care about mountain building?

Answer 2

1. Large scale transport of water, sediment, particulate and dissolved solids.
2. Short term weather patterns.
3. Long term climate.
4. Earthquakes build mountains.
5. Erosional processes build and destory mountain ranges.
6. Beautiful landscapes.

Question 3

What drives transport in terms of mountains and oceans?

Answer 3

Potential energy gradients due to gradient change.

Question 4

How do mountains influence climate?

Answer 4

Interact and disrupt the atmosphere to affect climate, leading to persistent spatial differences in rainfall.
This can affect vegetation, co2 uptake, habitats, weathering and water supplies.

Question 5

How can mountains help us understand past earthquakes?

Answer 5

Mountains contain a record of past earthquakes that can be used to understand and forcast future events.

Question 6

What ultimately drives mountain building?

Answer 6

Plate tectonics

Question 7

What cluster along plate boundaries?

Answer 7

Mountains and large scale earthquakes

Question 8

What can the Earth’s structure be defined by?

Answer 8

Its chemical or mechanical properties

Question 9

What is the chemical composition of the Earth?

Answer 9

Crust, upper mantle, lower mantle, outer core, inner core.

Question 10

What is the mechanic composition of the Earth?

Answer 10

Lithosphere, asthenosphere, lower mantle, outer core and inner core.

Question 11

What is the lithosphere?

Answer 11

Crust and top of upper mantle.
Mechanically strong and brittle deformation.

Question 12

What is the asthenosphere?

Answer 12

Remainder of the upper mantle. Mechanically weak, ductile deformation.

Question 13

What is the Earth’s crust?

Answer 13

The upper rigid part of the lithosphere. The crust is divided into either continental or oceanic crust.

Question 14

What is continental crust?

Answer 14

Thicker, more buoyant and silica-rich.
Loth of quartz rich rock.

Question 15

What is oceanic crust?

Answer 15

Thinner, denser and silica-poor.
Lots of basalts.

Question 16

What is the crust divided into?

Answer 16

Tectonic Plates

Question 17

What is the first principle of plate tectonic theory?

Answer 17

Thin, rigid plates. (Works well for oceanic plates, but less so for thicker, heterogeneous continents).

Question 18

What is the second principle of plate tectonic theory?

Answer 18

All deformation occurs at plate boundaries. (Works well for oceanic, not for continental).

Question 19

What is the third principle of plate tectonic theory?

Answer 19

Relative motion of plates is driven by asthenospheric convention, gravitational sliding.

Question 20

What is the fourth principle of plate tectonic theory?

Answer 20

Rates of relative motion are around 1 to 100 mm/yr.

Question 21

What is absolute motion?

Answer 21

All plates move relative to the centre of the Earth.

Question 22

What is relative motion?

Answer 22

How plates move comapred to each other.

Question 23

What does relative motion determine?

Answer 23

The behaviour at their boundaries.

Question 24

What are divergent plate boundaries?

Answer 24

A plate boundary where two plates move away from each other. New crust is formed when magma rises up between the plates.

Question 25

What are common at divergent plate boundaries?

Answer 25

Earthquakes

Question 26

What is crucial evidence for sea floor spreading at divergent plate boundaries?

Answer 26

Changes in Earth's magnetic field are recorded in the magma as it solidifies.

Question 27

What is an example of a divergent plate boundary?

Answer 27

Mid Atlantic Ridge, Iceland.

Question 28

What is an example of an oceanic-continental convergent plate boundary?

Answer 28

South America (Andes)

Question 29

What is an example of an oceanic-oceanic convergent plate boundary?

Answer 29

Aleutian Islands

Question 30

What is an example of an continental-continental convergent plate boundary?

Answer 30

Himalayas

Question 31

What landforms are found at an oceanic-continental convergence plate boundary?

Answer 31

Trench Volcanic arc

Question 32

What landforms are found at an oceanic-oceanic convergence plate boundary?

Answer 32

Trench Island arc

Question 33

What landforms are found at a continental-continental convergence plate boundary?

Answer 33

Mountain range

Question 34

What plate boundary is associated with mountain building?

Answer 34

Convergent

Question 35

What natural hazards occur at convergent plate boundaries?

Answer 35

Earthquakes and volcanic eruptions

Question 36

What is exhumation?

Answer 36

Movement of rock to the Earth's surface

Question 37

What is rock uplift?

Answer 37

Where one section of the Earth's surface moves up relative to another.

Question 38

What is tectonic rock uplift?

Answer 38

Via earthquakes and movement along faults.

Question 39

What is isostatic rock uplift?

Answer 39

Via gravity, due to buoyancy

Question 40

How does tectonic activity create mountains through uplift?

Answer 40

Tectonic activity creates high topography from repeated earthquakes on distinct faults. Causes the rock units to 'stack up'.

Question 41

What is an example of tectonic rock uplift building mountains?

Answer 41

Indian-Eurasian collision zone and the Himalayas. Indian plate subducts under the Eurasian plate.

Question 42

Who conceived the idea of the earthquake cycle?

Answer 42

Harry Reid after the 1906 San Francisco earthquake.

Question 43

Are plates elastic?

Answer 43

Yes, but the defromation in the earthquake is permanent.

Question 44

Are relative plate motion vectors contant over Myr time scales?

Answer 44

Yes

Question 45

What pattern did Reid notice?

Answer 45

A pattern of absolute offsets that could be mapped continuously along the fault. He inferred that this represented the release of elastic stress that had built up on the fault over time and then 'rebounded'.

Question 46

What is the earthquake cycle?

Answer 46

The frictional properties of the Earth's brittle upper crust gives rise to stick-slip behaviour as the sides of the fault are loaded by relative plate motion. Earthquake events release the built-up stress. The cycle is repeated because the plates continue to move.

Question 47

What the interseismic phase?

Answer 47

The time between earthquakes, as the stress begins to build.

Question 48

What is the coseismic phase?

Answer 48

Includes the earthquake event.

Question 49

What is the lithosphere?

Answer 49

Crust and top of upper mantle - home to tectonic plated.

Question 50

Difference between lithosphere and asthenosphere?

Answer 50

Lithosphere is like hard chocolate and asthenosphere is like melted chocolate.

Question 51

Along what type of boundary do we see mountain building?

Answer 51

Convergent

Question 52

What is tectonic rock uplift?

Answer 52

Where one section of the Earth's surface moves up relative to another due to earthquakes and movement along faults.

Question 53

Describe the different steps in the earthquake cycle.

Answer 53

Stick-slip behaviour. Interseismic phase- stress builds up along faults, rock deforms. Stress exceeds local rock strength. Coseismic phase- release of stress via earthquake causes slip.