mid term 3 Flashcards
(94 cards)
1
Q
Acid volcanos
A
- Zones of the ocean and continental crust (subduction)
- creates andesite, Rhyolite rock
2 kinds: - Lava domes formed only of lava layers, round shape
- Stratovolcano’s formed from lava and ash cone shape
2
Q
Basaltic volcanoes
A
- Widespread low layers of lava
- Spreads over a wide distance
- Looks like a hill side very flat
3
Q
Caldera
A
Volcano that has collapsed
* Empty magma chamber causing
ground to sink
* Cauldron-like depression
4
Q
Hazards
A
- Pyroclastic flow
- Lahars
5
Q
Lahars
A
- Mudflow or debris flow
- Composed of pyroclastic material, rock
debris and water - Caused from mixing with snow, lake
water, wet soil - Density of wet concrete
- Highly destructive
6
Q
Pyroclastic flow
A
- Collapse of part of a lava dome while it’s still active
- Fast-moving current of hot gas and volcanic material
7
Q
Jökulhlaups
A
- Glacier outburst flood
- Some are caused by subglacial volcanic eruption
- Lava melts large quantities of water
8
Q
Seismic waves
A
- The movement of the two pieces of crust (cm to meters)
releases seismic energy into the surrounding crust. - The shockwaves radiate outward from the focus and epicenter.
9
Q
Seismographs
A
Detects and records the motion of the ground
* P-waves (body waves) arrive first, followed by S-waves
* A network of seismographs or
seismometers can allow you to pinpoint the quake’s origin
10
Q
Foreshock
A
- A foreshock can happen before the
main shock. - Can be minutes, days or even
years! - Occurs for about 40% of
moderate to large earthquakes
11
Q
Aftershock
A
- An aftershock or a series of
aftershocks may occur after
the main shock.
12
Q
Focus
A
- A focus (or hypocenter) of
an earthquake is the
subsurface area along a fault
plane, where the motion of
seismic waves are initiated
13
Q
epicenter
A
- An epicenter is the area at
the surface directly above
the focus
14
Q
Richter scale
A
- Based on amplitude of seismic waves, which is related to
energy released.
15
Q
Moment magnitude scale
A
- the scale measures earthquake energy by fault movement, rupture size and rock strength
- Calculated from:
- a) the distance a fault is moved
- b) the amount of force required to move it.
16
Q
Damage potential
A
based on
- the location of focus and epicenter
- duration and amount of shaking
-soil and rock type in the area
- near slopes that can have land or mudlsides
- tsunami is near the ocean
- population concentration
17
Q
Liquifaction
A
- Water saturated, unconsolidated
sediments become liquid - Caused by shaking from seismic
waves - Can cause significant damage with
collapse of infrastructure
18
Q
Damage
A
- Fires
- Landslides
- Building collapse
- Infrastructure
19
Q
What is a glacier
A
- A moving mass of ice,
flowing downhill like a slow
river - Ice moves downhill due to
gravity - Two major ice sheets:
Greenland and Antarctic
20
Q
How to make a glacier
A
- Cold enough for snow to last
year round - Over time the snow
accumulates and increases in
density (snow gets
increasingly squished the
more it is buried by newer
snow)
21
Q
PROCESSES OF SNOW
METAMORPHISM
A
- Molecules transfer
between snow grains,
reducing the surface area - Thermodynamically unstable
(until a sphere shape) - Compaction causing
density increase
22
Q
Firn to ice transition
A
Snow → Soft and fluffy (low density, loose crystals).
Firn → Firm and airy (compacted but air can still move).
Ice → Solid and sealed (high density, air trapped as bubbles).
23
Q
Ablation
(removing mass)
A
- MELTING
- Affected by air temperature
- Albedo: very reflective surfaces reflect more sun (depends how
dark the ice surface is. Fresh
snow is the most reflective) - Ice can’t be above 0oC…just
melts more - Latent heat warms snow and ice
- CALVING
- Where blocks of ice break off the front of glaciers that flow into the sea or into lakes
- Creates icebergs
24
Q
Glacier Mass balance
A
- Mass balance: change in mass of an ice body or glacier over a period of time
- Positive mass balance: cold periods with lots of snow.
Snow build up > glacier melt. Glacier builds up and
advances down the valley. - Negative mass balance: warm periods with lots of melt. Melt > snow build up. Glacier thins and retreats up the valley.
25
Glacier mass balance
* Accumulation at higher
elevations
* More snow
* Colder temperatures
* Less melt
* Ablation at lower
elevations
* Warm enough to melt
26
Types of Glaciers:
- cirque
-Valley (Alpine) glacier
-Tidewater
glaciers
- ice cap
- ice sheets (Greenland)
- Ice sheets
(Antarctic)
- Ice shelves
27
cirque
- Bowl-shaped feature
- This is where glaciers
begin to form
- Very high up in the
mountains
- Tend to be North
facing in the N.hemisphere
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Valley (Alpine) glacier
- Flows through the
mountains (controlled by
topography)
- Erodes and removes
material changing a v-
shaped (river) valley into a
u-shaped
29
Tidewater
glaciers
* Glaciers that flow into the
ocean
* As they move into the deep
water, the ice starts to
float
* These glaciers ‘calve’ and
produce icebergs that float
out to sea
* Sensitive to warming ocean
waters (cause melt and
the retreat of these glaciers)
30
ice cap
- When there is enough ice
to cover topography (i.e
‘capping’ the underlying
rock)
- Forms a dome shape
31
ice sheets (Greenland)
- 81% of Greenland is
covered in ice
- The ice sheet is up to 3
km thick!
- Lots of lakes form on the
surface of the ice in the
summer
32
Ice sheets
(Antarctic)
- The Antarctic is the coldest and the
driest place in the world
- Largest ice sheet in the world (60 m
of sea level rise if it all melts)
- Has the oldest ice in the world (up to
1 million years giving us a record of
past climate)
- Divided into the West Antarctic Ice
Sheet (WAIS) and the East Antarctic
Ice Sheet (EAIS)
33
Ice shelves
- When glaciers or ice streams
flow into the ocean but don’t
break off they become ice
shelves
- Floating on the ocean so
melt more when the ocean
waters warm up
34
Supraglacial:
rivers
Moulin = Nature's water slide
Surface water enters the glacier through moulins, like a slide leading water straight to the glacier bed.
Summer = Water on the go
Warmer temperatures mean more melting, so there’s lots of water moving during the day in summer.
Winter = Almost no show
Usually no meltwater in winter, but occasionally there’s some depending on the conditions.
Antarctica = Too cold to flow
No surface water here because it’s simply too cold for melting to happen.
35
hwo do glaciers move
- when ice is under pressure it has lots of ice lying on top of it it becomes soft
- this is called ice creep
* In the top 30m of
the glacier, the ice is
brittle (as it’s not
under enough
pressure to flow)
and so it cracks.
- the cracks are called crevasses
36
Supraglacial:
Lakes
- Can either overflow into a river (like a normal lake).
Or crack through km’s of ice to the bed.
- Millions of m3 of water is added to the bed of the ice in a matter of hours
37
Subglacial
(water at the base of the ice)
* Water can flow by spreading
out at the bottom of the ice
either over the rock or into
sediments
* Lots of lubrication for the ice
* Causes fast flow
* Sometimes the water melts
out large channels into the
base of the ice that removes
the rest of the water quickly
* Less lubrication for the ice
* Causes ice flow to slow down
38
Glacial erosion
* When ice moves across a
surface, material is eroded by:
* Abrasion
* Plucking
* Also glacio-fluvial action (i.e.
water)
* Erosion is helped by weakness in the rock, such as cracks or
joints.
39
Abrasion caused by Glacial movement
* Rocks frozen in the ice drag
along the bedrock
* Create scratches in the rock
called striations
40
Glacial plucking
* Subglacial rocks are broken up by freeze-
thaw action.
* Ice freezes onto rock at the base and pulls
it away as it flows downhill.
* The rocks frozen in the ice later act as
abrasion and erosion agent
41
U-shaped Valley
* Glaciers produce valleys with "U"
shaped cross-section, steep walls
and generally broad & flat floor
* Steepened, deepened and widened
42
Fjords
* U-shaped valleys filled with sea water
* Due to sea level rise as the large ice sheets melted after the last
glacial period
43
Hanging valley
* A former tributary above a U-shaped
glacier valley
* Higher than the floor of the main valley
* Main glacier cuts off end of valley = truncated spur
Milford Sound, New Zealand
Truncated spur
44
Erratics
* Rocks of varying shapes & sizes
* often fall on the surface of the
glacier from the mountains that it
flows through
* Moved a long distance by glacier
(or iceberg )
* Often identifiable from their
different composition compared to
where they are deposited
45
Glacial sediments
All ice-related deposits are called
glacial drift. Two main types:
- Till (primary deposition)
- Stratified drift (secondary
deposition)
46
1. Till (primary deposition)
- Sediment deposited directly by glacier
ice without disturbance
– Texture: Unsorted, very angular,
mixture of fine and coarse material
– Structure: Unstratified (all mixed up)
47
2. Stratified drift (secondary
deposition)
Formed by: Water from melting glaciers (glacial meltwater).
Texture: Well sorted mix of clay, silt, sand, gravel, and boulders.
Structure: Layered (stratified) from water flow, with parallel layers.
48
Moraines
Ground moraine = Bottom blanket
End moraine = Glacier’s stop sign
Lateralmoraine = Side stripes
Medial moraine = Middle merge stripe.
49
Terminal moraine
* The glacier acts as a bulldozer
* Location of the moraine shows maximum
extent of the glacier
* May have ridge form
* And, terminal moraines often impound
proglacial lake
50
Lateral moraines
* Till ridges along valley
sides
* Mostly angular & unsorted
material
* Mark previous “width” of
the glacier
51
Eskers
* Sinuous, meandering ridge made of course sand
and gravel.
* Deposited from englacial/subglacial rivers
* Show the direction of glacial water flow
52
kettle lakes
Formed by: Melting ice blocks buried under sediment.
Process: As the ice melts, the depression gets bigger.
Characteristics: Round, deep, and often found in clusters.
Common in: Southern Ontario.
53
Drumlines
* Elongated ridges of till
* Formed under the ice and shaped by ice flow
* Parallel with flow
* Steep end (oval or rounded) faces where ice
came from
* Lee side (downflow side) tapers
54
Geomorphology
* Geomorphology (morph means shape or form) is the
science of landforms including origin, evolution, form, and spatial distribution of landforms.
55
Denudation
* Process that wears
away or rearranges
landforms
* Weathering
* Mass movement
* Erosion
* Transportation
* Deposition
56
Slope stability
For material to move: Gravity needs to overcome friction, resistance to movement, and how the particles stick together.
Movement happens if:
The slope is steep enough for gravity to push the material.
Rain or wind can loosen the material.
57
Weathering
* Weathering = process
that breaks down rocks
1. Physical weathering
(mechanical
weathering)
2. Chemical weathering
(dissolves rock)
58
Regolith
* Regolith: Broken up material and rock on the surface of bedrock
due to weathering
* Bedrock: Consolidated, solid rock = PARENT ROCK
59
Parent Material
The material soils form from, like loose sediments or weathered rock
60
Physical weathering: Frost weathering
* Freeze-thaw action
* Water expands when it freezes (by 9%), and fractures rock
* Dominant process in arctic and high-mountain environments
61
Physical weathering: Salt weathering
* Water evaporates from sandstone pores, leaving salt
crystals behind.
* Crystals grow and disintegrate rock grains.
* Occurs in arid and semiarid regions, and coastal regions.
62
Physical weathering: Pressure-release
* Exfoliation: rocks peels or slips off in sheets (also called sheeting)
* Rock is exposed at the surface, releasing pressure, so rock expands slightly
63
Chemical weathering
* Chemical breakdown of minerals in rock through exposure to
precipitation and water
* Most effective in warm, moist climates
64
Chemical weathering: acid rain
* Water vapour can dissolve carbon
dioxide producing carbonic acid
* Rain acidity has been increasing
in Europe since the industrial
revolution
65
Chemical weathering: spheroidal
weathering
* Edges of rocks become rounded
* Water penetrates the rock joints and
dissolves weaker minerals
* Rocks can shed shells like an onion
66
Chemical weathering: oxidation
* ‘rusting’ – iron oxide
* Iron is removed from the minerals in the rock
* Rock is then more susceptible to disintegration
67
Chemical weathering: carbonate
dissolution
Rain contains carbonic acid that dissolves limestone, a process called carbonation. This shapes landscapes with limestone, creating karst topography
68
Karst: sinkhole
* Circular depressions in
the ground
* Either from collapse
into underground
cavern
* Or slow subsidence of
surface material
because of dissolving
of limestone
69
Karst: caves and caverns
Formed by: Water dissolving limestone.
Location: Just below the water table.
Speleothems: Calcium carbonate redeposits in the caves, forming structures like stalactites and stalagmites.
70
Karst: speleothems
* Stalactites grow down
from the ceiling
* Stalagmites grow up
from the floor
* They can join to form a
column
71
Mass Wasting Processes
* Steepness of slope determines when loose material comes to rest, depending on size and
texture of grains
* Driving force: gravity – steepness of slope
* Resisting Force: shear strength of material, cohesiveness and internal friction working against
mass movement
* Angle of repose: balance of driving and resisting forces
72
Causes of mass wasting
* Weathering (e.g. freeze-
thaw action weakens rock
joints)
* Saturation of slope (e.g.
heavy rain)
* Oversteepening from
erosion (river or ocean
erodes base)
* Earthquake shakes debris
loose or fractures rock
73
Classes of mass movement
* Material can:
1. Fall
2. Slide
3. Flow
4. Creep
74
types of mass wasting
Dryer & Slower:
Soil Creep: Gradual downhill soil movement.
Moderate Speed:
Translational Slide: Moves along a flat surface.
Rotational Slide (Slump): Moves on a curved surface, often due to water on clay layers.
Faster & Wetter:
Earthflow: Slow to moderate flow of saturated soil.
Debris Avalanche: Rapid movement of loose debris.
Mudflow: Fast-moving flow of water and fine sediments.
Fastest & Steepest:
Rockfall: Sudden free fall of rocks from cliffs.
75
Initiation of rivers
* Water moves downslope over the surface = overland flow --> Sheetflow – thin film over the surface --->Rills – small grooves eroded into the soil by water ----> Gullies – rills eroded into larger features ----> Streams – water flow in valley floors fed by gullies ----> Rivers – larger systems fed by many streams
76
Drainage Basin
* Also called a watershed
* The land area that feeds a
particular river system
* Separated by high ground
called ridge
77
Continental
divide
* Separates drainage
basins that empty into
different oceans/seas
surrounding a continent
* These major drainage
basins are made up of
multiple smaller
drainage basins
* Size of drainage basin
impacts available water
resources
78
Stream gradient
* Slope of the channel
* Drop in elevation over a distance
* Generally steeper slope at the headwaters and shallower
downstream
* the gradient determines how fast the water will flow
79
Base level
* Lowest level that a stream can erode its valley to
* Ultimate base level = sea level
* Local base level can limit regional erosion (e.g. lakes,
dams)
80
Stream discharge (Q)
* Discharge (or runoff) is the
streamflow volume
passing a point (e.g., outlet of a
watershed) in a
given unit of time.
* Discharge is calculated as:
Q = w × d × v
* where w is width and d is depth for a specific
cross-section of the channel, and v is the velocity.
81
The Hydrograph
- Base flow: low discharge during dry periods, from groundwater
- peek flow: Highest discharge after rainfall
- Lag time: delay between rainfall and peek flow, influenced by watershed surface
82
erosion
* Erosion in fluvial systems is the process by which
water dislodges, dissolves, or removes weathered
surface material.
* Affected by discharge and the channel gradient
83
Hydraulic action
* Performed by water alone
* The force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks
and gradually wears it away.
84
Abrasion
* rocks carried along by the river wear down the
river bed and banks
* Rocks have to be a stronger material than the
bed
85
Attrition
* Rocks being carried by the river smash together and
break into smaller, smoother and rounder pieces of
rock.
86
Corrosion/solution
* Rocks and
sediments dissolved
by acid in the water
* Chemical
weathering
* E.g. limestone,
soluble salts
87
Transportation/sediment load
* Suspended load: light, fine material is carried
within the river flow as long as velocity >0
* Traction: large boulders and rocks are rolled
along the bed
* Saltation: small pebbles and stones are bounced
along the bed
* Solution load: dissolved load is carried along
with the river flow.
88
Flood sediment
transport
Larger discharge = larger
erosion and transport rates
* Degradation = channel
erodes (i.e. when flood water
build)
* Aggradation = deposition (i.e.
flood waters drop, energy
reduced and sediment
accumulates at the bed)
89
depostion
landforms of material caused by river meanders
90
river meanders
* Where channel slope is
gradual
* Finding the path of least
effort/resistance
91
Floodplains
* flat, low-lying area adjacent to a
channel
* subjected to recurrent flooding when
flow is high
* Receding water leaves alluvial deposits
92
levees
-formed when rivers overflow and deposit sediment along banks
- create natural ridges that reduce future flooding but can trap floodwater
93
Alluvial fans
- Found in arid areas where streams exit mountains
- Flash floods slow down on flat valleys, dropping sediment in layers at the mountain base.
Arid: very dry with little no rainfall, making it difficult for plants to grow. common in desserts
94
Delta
* At the mouth of the river where it reaches the base level
* River slows down quickly as it enters a lake or the ocean
* Reduced energy = deposition of sediment
* Deposition plain = delta
