mid term 3 Flashcards
Acid volcanos
- 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
Basaltic volcanoes
- Widespread low layers of lava
- Spreads over a wide distance
- Looks like a hill side very flat
Caldera
Volcano that has collapsed
* Empty magma chamber causing
ground to sink
* Cauldron-like depression
Hazards
- Pyroclastic flow
- Lahars
Lahars
- 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
Pyroclastic flow
- Collapse of part of a lava dome while it’s still active
- Fast-moving current of hot gas and volcanic material
Jökulhlaups
- Glacier outburst flood
- Some are caused by subglacial volcanic eruption
- Lava melts large quantities of water
Seismic waves
- 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.
Seismographs
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
Foreshock
- A foreshock can happen before the
main shock. - Can be minutes, days or even
years! - Occurs for about 40% of
moderate to large earthquakes
Aftershock
- An aftershock or a series of
aftershocks may occur after
the main shock.
Focus
- A focus (or hypocenter) of
an earthquake is the
subsurface area along a fault
plane, where the motion of
seismic waves are initiated
epicenter
- An epicenter is the area at
the surface directly above
the focus
Richter scale
- Based on amplitude of seismic waves, which is related to
energy released.
Moment magnitude scale
- 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.
Damage potential
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
Liquifaction
- Water saturated, unconsolidated
sediments become liquid - Caused by shaking from seismic
waves - Can cause significant damage with
collapse of infrastructure
Damage
- Fires
- Landslides
- Building collapse
- Infrastructure
What is a glacier
- A moving mass of ice,
flowing downhill like a slow
river - Ice moves downhill due to
gravity - Two major ice sheets:
Greenland and Antarctic
How to make a glacier
- 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)
PROCESSES OF SNOW
METAMORPHISM
- Molecules transfer
between snow grains,
reducing the surface area - Thermodynamically unstable
(until a sphere shape) - Compaction causing
density increase
Firn to ice transition
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).
Ablation
(removing mass)
- 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
Glacier Mass balance
- 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.
Glacier mass balance
- Accumulation at higher
elevations - More snow
- Colder temperatures
- Less melt
- Ablation at lower
elevations - Warm enough to melt
Types of Glaciers:
- cirque
-Valley (Alpine) glacier
-Tidewater
glaciers - ice cap
- ice sheets (Greenland)
- Ice sheets
(Antarctic) - Ice shelves
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
Valley (Alpine) glacier
- Flows through the
mountains (controlled by
topography) - Erodes and removes
material changing a v-
shaped (river) valley into a
u-shaped
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)
ice cap
- When there is enough ice
to cover topography (i.e
‘capping’ the underlying
rock) - Forms a dome shape
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
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)
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
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.
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
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
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
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.
Abrasion caused by Glacial movement
- Rocks frozen in the ice drag
along the bedrock - Create scratches in the rock
called striations
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
U-shaped Valley
- Glaciers produce valleys with “U”
shaped cross-section, steep walls
and generally broad & flat floor - Steepened, deepened and widened
Fjords
- U-shaped valleys filled with sea water
- Due to sea level rise as the large ice sheets melted after the last
glacial period
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
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
Glacial sediments
All ice-related deposits are called
glacial drift. Two main types:
- Till (primary deposition)
- Stratified drift (secondary
deposition)
- 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)
- 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.
Moraines
Ground moraine = Bottom blanket
End moraine = Glacier’s stop sign
Lateralmoraine = Side stripes
Medial moraine = Middle merge stripe.
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
Lateral moraines
- Till ridges along valley
sides - Mostly angular & unsorted
material - Mark previous “width” of
the glacier
Eskers
- Sinuous, meandering ridge made of course sand
and gravel. - Deposited from englacial/subglacial rivers
- Show the direction of glacial water flow
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.
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
Geomorphology
- Geomorphology (morph means shape or form) is the
science of landforms including origin, evolution, form, and spatial distribution of landforms.
Denudation
- Process that wears
away or rearranges
landforms - Weathering
- Mass movement
- Erosion
- Transportation
- Deposition
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.
Weathering
- Weathering = process
that breaks down rocks
1. Physical weathering
(mechanical
weathering)
2. Chemical weathering
(dissolves rock)
Regolith
- Regolith: Broken up material and rock on the surface of bedrock
due to weathering - Bedrock: Consolidated, solid rock = PARENT ROCK
Parent Material
The material soils form from, like loose sediments or weathered rock
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
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.
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
Chemical weathering
- Chemical breakdown of minerals in rock through exposure to
precipitation and water - Most effective in warm, moist climates
Chemical weathering: acid rain
- Water vapour can dissolve carbon
dioxide producing carbonic acid - Rain acidity has been increasing
in Europe since the industrial
revolution
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
Chemical weathering: oxidation
- ‘rusting’ – iron oxide
- Iron is removed from the minerals in the rock
- Rock is then more susceptible to disintegration
Chemical weathering: carbonate
dissolution
Rain contains carbonic acid that dissolves limestone, a process called carbonation. This shapes landscapes with limestone, creating karst topography
Karst: sinkhole
- Circular depressions in
the ground - Either from collapse
into underground
cavern - Or slow subsidence of
surface material
because of dissolving
of limestone
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.
Karst: speleothems
- Stalactites grow down
from the ceiling - Stalagmites grow up
from the floor - They can join to form a
column
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
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
Classes of mass movement
- Material can:
1. Fall
2. Slide
3. Flow
4. Creep
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.
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
Drainage Basin
- Also called a watershed
- The land area that feeds a
particular river system - Separated by high ground
called ridge
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
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
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)
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.
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
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
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.
Abrasion
- rocks carried along by the river wear down the
river bed and banks - Rocks have to be a stronger material than the
bed
Attrition
- Rocks being carried by the river smash together and
break into smaller, smoother and rounder pieces of
rock.
Corrosion/solution
- Rocks and
sediments dissolved
by acid in the water - Chemical
weathering - E.g. limestone,
soluble salts
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.
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)
depostion
landforms of material caused by river meanders
river meanders
- Where channel slope is
gradual - Finding the path of least
effort/resistance
Floodplains
- flat, low-lying area adjacent to a
channel - subjected to recurrent flooding when
flow is high - Receding water leaves alluvial deposits
levees
-formed when rivers overflow and deposit sediment along banks
- create natural ridges that reduce future flooding but can trap floodwater
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
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
