Topic 4 - Notes
Weathering – breakdown of rocks into smaller pieces
Two kinds:
(1) physical – breakdown without changing composition ex) frost
action (wedging)– freezing and thawing of water to break rocks apart, root action
- tree roots grow into rocks and break them apart.
(2) chemical – breakdown by changing the composition ex) oxidation
– reaction with oxygen (rust), acids – dissolve certain minerals, hydration – water
dissolves many Earth substances
Relationships:
between weathering rate (how fast it breaks down) and:
Particle size – decrease particle size will increase weathering
Surface area – increase surface area will increase weathering
between particle size and surface area:
Decrease particle size will increase surface area, therefore increase
weathering
between chemical weathering and climate:
Increase temperature and moisture will increase chemical weathering
between particle size/ density and settling rate:
Larger particles settle faster
More dense particles settle faster.
between shape and settling rate:
Round settle faster, flat settle slower.
between resistance and weathering:
More resistant weather slower, quartz vs.
calcite
Erosion – movement of sediment
Deposition – when sediment stops moving, it gets put in place by something
Water (streams and Rivers) - #1 agent of erosion
Products – round and smooth particles
Transport – rolling and bouncing, suspension, solution, floating
Sorting – Horizontal: largest near the shoreline, smallest out far
Vertical: largest on the bottom, smallest on the top
Things to know:
River profiles, aerial view, cross sections, stages of stream
development, energy in a stream: where there is erosion, deposition, etc. (erosion
on outside of a curve,
deposition on inside of a curve)
More water (discharge) means faster water, which will increase
erosion
Rivers make V-shaped valleys
Glaciers – large bodies of moving ice
Continental – ice sheets
Alpine – mountain glaciers
Products – scratch and polish rocks
Deposits – unsorted (till) mixed sediment and unlayered
U-shaped valleys – the glacier creates a u-shape valley as gravity
pulls it downhill
Wind – the stronger the wind blows, the larger the particles it can
transport
Products – frosted and pitted
Deposits – crossbeds and dunes
Glaciers
Continental Glaciers – a.k.a. ice sheets (Greenland, Antarctica)
- Move by gravity, downhill, or north to south
- Products: scratched and polished(striations)
- Advance – glacier moves forward
- Retreat – glacier melts from front to back
- Till – unsorted deposit from a glacier, mixed sizes, shapes,
compositions
- Erratics – large drop-stones, boulders, etc. from a glacier
- Moraines – deposits at the leading edges of glaciers
-
o Terminal moraines – this is where the glacier stopped moving
forward
o Lateral moraines – this is where the glacier stopped moving to
the side
Outwash – the meltwater stream coming from the glacier, these will
sort deposits
Outwash plain – the area where the meltwater flows out
Kame –delta shaped meltwater deposit
Esker – ridge of sediment deposited by a glacier
Drumlin- large tear-drop shape deposit , shows direction of movement
Kettle- is a hole or lake formed by a buried ice block from the glacier
Pothole – this is feature formed by fast moving water, a whirlpool and
sediment
Landscape Development - page 2 ESRT
Landscape – region of Earth’s surface where physical features are related by a
common origin
Stream Drainage Patterns – the shape of the streams as seen from the air
Gradient (slope) – a way to describe the land because it is a measurable
characteristic and useful because it shows the development of soils
The three major types of landscapes are distinguished by gradient, elevation, and
rock structure. ESRT page 2. They are:
1. Mountains: high elevation, non-sedimentary rocks, distorted/ uplifted
2. Plateaus: high elevation, undistorted horizontal rocks
3. Plains (lowlands): low elevation, level surface, sedimentary rocks
Landscape boundaries – consist of characteristics of the landscape features with
structure changes in the rock, Ex) from horizontal rocks to folded rocks = plains to
mountains
Two forces that alter landscapes:
1. Uplifting: displacing of rock strata to raise the land, Ex) volcanic action, plate
tectonic events, etc.
2. Leveling(subsidence): weathering, erosion, deposition, the acts of breaking
down and removing the strata
Moisture and temperature – influence the rate of development and characteristics
of the landscape (arid vs. humid)
Four drainage patterns:
1. random: (dendritic) horizontal sedimentary rocks with little difference in rock
resistance
2. trellis: found in folded rocks with great difference in rock resistance
3. radial: domed structure with little difference in resistance
4. annular: concentric circles with great difference in rock resistance