Active tectonics and mountain environments

Question 1

What is the lithosphere?

Answer 1

The crust and uppermost mantle; mechanically strong and brittle.

Question 2

What is the asthenosphere?

Answer 2

Part of the upper mantle; mechanically weak and ductile.

Question 3

What are the main layers of Earth by composition?

Answer 3

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

Question 4

What are tectonic plates?

Answer 4

Rigid segments of the lithosphere that move over the asthenosphere.

Question 5

What drives plate movement?

Answer 5

Mantle convection and gravitational sliding.

Question 6

What are the three main plate boundaries?

Answer 6

Divergent, convergent, and transform.

Question 7

What happens at divergent boundaries?

Answer 7

Plates move apart; new crust forms (e.g., mid-ocean ridges).

Question 8

What happens at convergent boundaries?

Answer 8

Plates collide, forming mountains, volcanoes, and earthquakes.

Question 9

What happens at transform boundaries?

Answer 9

Plates slide past each other, often causing earthquakes.

Question 10

What is a subduction zone?

Answer 10

Region where one tectonic plate sinks beneath another.

Question 11

What is tectonic rock uplift?

Answer 11

Rocks are pushed upward due to fault movement.

Question 12

What is isostatic rock uplift?

Answer 12

Rocks rise due to removal of overlying mass (e.g., erosion or ice melt).

Question 13

What is the earthquake cycle?

Answer 13

Repeating cycle of stress accumulation and release on faults.

Question 14

What are the phases of the earthquake cycle?

Answer 14

Interseismic, coseismic, and post-seismic.

Question 15

What is stick-slip behavior?

Answer 15

Stress builds until it’s suddenly released by fault slip.

Question 16

What is a characteristic earthquake model?

Answer 16

Same size earthquakes occur at regular intervals.

Question 17

What is a time-predictable model?

Answer 17

Next quake’s timing depends on size of previous quake.

Question 18

What is a slip-predictable model?

Answer 18

Next quake’s size depends on time since last quake.

Question 19

What is the clustered model?

Answer 19

Quakes occur in time-space clusters, not predictable.

Question 20

What causes surface uplift?

Answer 20

Rock uplift minus denudation.

Question 21

What is denudation?

Answer 21

The removal of material from the Earth’s surface by erosion.

Question 22

What is exhumation?

Answer 22

The process of rocks moving to the surface.

Question 23

What is the angle of repose?

Answer 23

The steepest angle at which loose material remains stable.

Question 24

What is a fault scarp?

Answer 24

Step or cliff on the ground surface caused by fault movement.

Question 25

How do earthquakes build mountains?

Answer 25

Repeated earthquakes along faults uplift terrain.

Question 26

What is a debris flow?

Answer 26

A fast-moving slurry of sediment and water.

Question 27

What is sediment routing?

Answer 27

The path sediment takes from hillslopes to oceans.

Question 28

What is the role of erosion in mountain building?

Answer 28

Erosion removes material and can lead to isostatic uplift.

Question 29

How does slope affect sediment transport?

Answer 29

Steeper slopes increase sediment flux.

Question 30

What is bedrock landsliding?

Answer 30

Deep landslides involving entire hillslopes.

Question 31

What is the sediment yield?

Answer 31

Sediment load divided by the drainage area.

Question 32

What controls sediment yield?

Answer 32

Slope, rainfall, vegetation, and basin size.

Question 33

Where are sediment yields highest?

Answer 33

In steep, wet, small mountain basins.

Question 34

What is sediment provenance?

Answer 34

The origin of sediment, identified via geochemistry.

Question 35

How do neodymium isotopes help in provenance?

Answer 35

They trace source rocks in sediment.

Question 36

What are sediment accumulation rates?

Answer 36

How quickly sediment is deposited over time.

Question 37

What causes drainage reorganization?

Answer 37

Tectonics, fault movement, or river capture.

Question 38

What is a sediment core?

Answer 38

Cylindrical sample from sediment layers used to study past environments.

Question 39

How does erosion influence tectonics?

Answer 39

It can create space, impacting faulting and uplift.

Question 40

What is a long profile?

Answer 40

Elevation of a river plotted from source to mouth.

Question 41

What is the slope-area relationship?

Answer 41

Slope generally decreases with increasing drainage area.

Question 42

What causes hillslopes to transition to channels?

Answer 42

Increase in drainage area and water flow.

Question 43

What defines a hillslope?

Answer 43

Land surface connecting ridges to streams.

Question 44

What defines a channel?

Answer 44

A landform where water and sediment converge.

Question 45

What tools help map mountain morphology?

Answer 45

Topographic maps, satellite imagery, DEMs.

Question 46

What are soil-mantled landscapes?

Answer 46

Landscapes with smooth hillslopes and thick soils.

Question 47

What is diffusive transport?

Answer 47

Slow movement of sediment grain-by-grain.

Question 48

What is a landslide?

Answer 48

Mass movement of rock/soil downslope due to gravity.

Question 49

What triggers landslides?

Answer 49

Earthquakes, rainfall, slope oversteepening.

Question 50

How do debris flows differ from landslides?

Answer 50

They involve water and behave like slurry.

Question 51

What are tectonic fluxes?

Answer 51

Input of material to a mountain range by tectonics.

Question 52

What are erosional fluxes?

Answer 52

Output of material from a mountain range by erosion.

Question 53

What is sediment load?

Answer 53

Mass of sediment leaving a basin per time.

Question 54

How is sediment transported in rivers?

Answer 54

As suspended load, bed load, and solutes.

Question 55

What is the global average suspended sediment yield?

Answer 55

116 tonnes/km²/year.

Question 56

What affects bed load transport?

Answer 56

Particle size and stream energy.

Question 57

What is aeolian sediment transport?

Answer 57

Wind-driven movement of sediment.

Question 58

Why do large basins have lower yields?

Answer 58

Because of storage and less intense erosion.

Question 59

What is the role of precipitation in erosion?

Answer 59

Higher rainfall increases erosion and sediment yield.

Question 60

How does mountain topography affect precipitation?

Answer 60

Influences atmospheric circulation and rain distribution.

Question 61

How does uplift of the Tibetan Plateau affect climate?

Answer 61

Enhances monsoon intensity and pattern.

Question 62

What is the South Asian monsoon?

Answer 62

Seasonal wind bringing heavy rain to the Indian subcontinent.

Question 63

What is topographic relief?

Answer 63

Difference in elevation between high and low points.

Question 64

What is uniformitarianism?

Answer 64

The present is the key to the past.

Question 65

What is neocatastrophism?

Answer 65

View that rare, extreme events shape Earth's history.

Question 66

What is a black swan event?

Answer 66

Rare, unpredictable event with major impact.

Question 67

What is magnitude-frequency distribution?

Answer 67

Describes how often events of various sizes occur.

Question 68

What is the Gutenberg-Richter law?

Answer 68

Describes frequency of earthquakes as a function of magnitude.

Question 69

What is the moment magnitude scale (Mw)?

Answer 69

Measures energy released by an earthquake.

Question 70

What is seismic moment?

Answer 70

A measure of earthquake size based on fault area and slip.

Question 71

How does Mw scale increase with energy?

Answer 71

Each +1 unit releases ~30x more energy.

Question 72

What is peak ground acceleration (PGA)?

Answer 72

Maximum ground shaking during an earthquake.

Question 73

What are seismic swarms?

Answer 73

Clusters of small earthquakes in a short time.

Question 74

What makes earthquake prediction difficult?

Answer 74

Variability in stress, strength, and timing.

Question 75

How are earthquake probabilities modeled?

Answer 75

Using past data and Gutenberg-Richter relationships.

Question 76

What is the angle of response?

Answer 76

Slope threshold for landsliding.

Question 77

What is debris flow aggradation?

Answer 77

Sediment buildup in channels due to insufficient transport.

Question 78

What are bedrock hillslopes?

Answer 78

Steep slopes with thin or no soil, prone to large landslides.

Question 79

How does sediment grain size vary downstream?

Answer 79

It generally decreases.

Question 80

What are sediment routing systems?

Answer 80

Networks moving sediment from source to sink.

Question 81

What are the impacts of extreme earthquakes?

Answer 81

Mass fatalities, infrastructure damage, and landscape change.

Question 82

What is the impact of tectonics on drainage patterns?

Answer 82

Can redirect rivers and alter sediment pathways.

Question 83

How do rivers capture drainage?

Answer 83

Through headward erosion and faulting.

Question 84

What is the significance of sediment records?

Answer 84

They reveal past tectonic and climatic changes.

Question 85

What is the importance of mountain erosion?

Answer 85

Shapes topography, exposes rocks, affects climate.

Question 86

How does isostasy maintain mountain height?

Answer 86

Crust rebounds as material is eroded.

Question 87

What are the challenges of erosion rate data?

Answer 87

Short observation times, variability, and rare events.

Question 88

What is a hazard cascade?

Answer 88

A sequence of related natural hazards (e.g., quake to landslide to flood).

Question 89

Why are debris flows hazardous?

Answer 89

They move fast, carry large debris, and occur suddenly.

Question 90

What is the importance of high b-values?

Answer 90

Indicate more small earthquakes, fewer large ones.

Question 91

What is the benefit of early warning systems?

Answer 91

Mitigate impacts of extreme events despite unpredictability.

Question 92

What is the role of fault scarp analysis?

Answer 92

Helps infer past seismic activity and mountain growth.

Question 93

What happens when faults cluster?

Answer 93

Increase in local hazard due to stress transfer.

Question 94

What affects the frequency of extreme events?

Answer 94

Geological setting, fault behavior, and clustering.

Question 95

How do sediment studies aid tectonic models?

Answer 95

Reveal erosion rates, source areas, and timing of uplift.