Weathering & Erosion

I. Weathering: is the breakdown of rock due to exposure to the atmosphere.

A. ___________________________: any process that causes rocks to break down to smaller pieces of the same material.

1. Frost Action

a) Frost Wedging: water that’s found in __________ of bedrock freezes & expands causing the crack to get larger.

b) exfoliation: the outer layer of a rock expands & ________________ as it’s heated by the sun…this causes the outer layer to weaken & crumble.

b) Plant Action: the roots of plants exert enough pressure to crack a rock.

Eg: grass growing in the cracks in the road will expand as the roots grow.

· ________: looks green carpet

· lichens: looks like green scales

Both grow on smooth surfaces & causes cracks to form

2. Abrasion:

3. Rocks rub against each other during __________________.

4. B. Chemical Weathering: breakdown of rock resulting in a change in ____________________.

1. Three substances responsible for chem’l weathering:

a) Oxygen: 21% of the atmosphere is O2; ___________________ is the addition of O2 .

Eg: (4) Fe + (3) O2 2 (Fe2O3)

iron + oxygen ____________________ (rust)

Copper (cu) will turn green when oxidized.

b) water: H2O hydration:

· ____________ up the process of rusting

· may also cause minerals to dissolve; this is how caves are formed.

c) Carbon Dioxide: CO2 from burning of __________________. It combines w/ H2O to form carbonic acid…this is what puts the “fizz” in carbonated drinks.

d) Pollutants: substances emitted into the atmosphere by humans.

Eg: Sulfur (S) combines w/ H2O to form sulfuric acid + _________________.

· Rain is naturally acidic but this increase causes an increase in the rate of weathering.

II. Rate of Weathering

A. Factors that affect weathering

1. Particle size: smaller particles will __________________ faster b/c there’s more surface area.

Eg: sugar granules v. sugar cube

2. Mineral composition: the harder the mineral, the more resistant to abrasion. Some minerals are soluble in H2O & even more soluble when H2O is acidic.

3. __________________: average conditions of temperature & humidity.

a) Physical weathering: requires moisture & a temperature that_____________________.

b) Chemical Weathering: more prevalent in warm, moist climates; may also be affected by local conditions such as pollution

III. Soil: accumulation of loose, _________________ material that covers much of the earth's surface. It contains weathered rock, water, air, bacteria, & decayed plant material.

A. Types of Soil

1. Residual: formed in place- the soil has the same characteristics as the rock below it.

2. Transported soil: formed from ___________________ that were deposited

******

I. Erosion: transporting of sediments

A. Agents of erosion:

1. water: rain, streams, waves, & currents

2. ____________________

3. ____________________

4. Glaciers

B. Streams: movement of H2O downhill thru channels by gravity

1. 4 ways sediments are transported in a stream:

a) Solution: _____________ particles are dissolved & carried downstream.

b) ________________: or bed-load- rolling, sliding, or bouncing.

c) Floatation: particles < dense than H2O will be carried @ the ______________.

d) Suspension: particles: particles w/the same density will remain suspended as they move.

2. Velocity: as the velocity increases, _________________________________________________.

a) Velocity is affected by:

· Gradient: __________________: as the gradient increases, the velocity increases.

· ______________: amount of H2O; as the discharge increases, the velocity increases, Flooding = > erosion.

· Location w/in a stream channel

C. Formation of a Stream

1. Watershed or Drainage Basin: all the land drains into a body of H2O directly or thru tributaries.

· Tributaries: are _____________ streams that empty into bigger ones.

a) Divide: high point that separates one H2O shed from another.

2. ___________Streams: young streams

· Starts as water flowing down a hill moving sediments

· Water will seek out the ________________________ & create a channel

· ***new stream will generally have a _____-shaped valley w/STEEP sides.

2. Mature Streams:

a) Overtime the stream valley _____________ & the slopes become < steep.

b) The velocity of the H2O will slow down & deposition occurs.

4. Formation of a Meander (curve)

a) As the velocity _____________________ due to the widening of the stream channel the water begins to flow around obstacles.

b) As water flows around the obstacle, erosion occurs on the outside of the curve & deposition will occur on the inside.

c) ______________- when the flooding occurs in a mature stream, the water flows over the land instead of flowing around the meander.

_____________- when a cutoff becomes the main channel flow the meander is eliminated forming an oxbow lake.

How meanders grow laterally through erosion (outside bend) and sediment deposition (inside bend, point bar). When the loops get too large and consume too much energy (friction), the river will eventually find a less energetically "taxing" shortcut, and a part of the old channel will be abandoned and becomes an oxbow lake.

C. ___________________________________

1. Only moves smaller particles- sand, silt, & clay

2. Occurs in dry areas w/little vegetation to hold sediment in place

3. Results in abrasion of larger particles.

· ___________________: angular rocks eroded by wind

E. Erosion by Gravity: also called mass ___________________.

1. Any size sediments will roll, slide, or fall downhill b/c of gravity. Eg: rock slide, mud slide, slump, & _________________.

Glaciers

Glaciers results in mostly unsorted deposits w/melt _________ sorting some of the deposits. Two types of glaciers:

1. Alpine Glaciers: also called valley glaciers, form @ hi elevations; they carve out _______shaped valleys.

2. Continental Glaciers: cover large areas of land during _____________________.

· Responsible for shaping much of NY

· N. America was covered w/ice about 20,000 yrs. ago

· There have been ______________________ over the past 2 million yrs.

As the ice melts, the sediments are deposited

3. Feature formed by glaciers:

a) __________________: line of sediment; terminal moraine-deposit @ the southern end of a glacier.

b) Kettle Lake: large chunks of ice left behind eventually melt, leaving behind an impression that fills w/______

c) _________________________: tear shaped ________________ that were pushed by glaciers

d) Erratics: large _________________dropped by the glacier

e) Eskers: long narrow deposits that are formed by melt_____________ flowing under the glacier

f. Outwash: the material deposited by the debris-laden meltwater

4. ___________________: shiny surface left behind as the glacier scrapes any loose sediment from bedrock.

5. Glacial Striations: or Grooves- scratches that formed as a result of large boulder frozen to the ___________ of the glacier being ______________ across the ___________________.

F. Erosion by Glaciers

1. Formation of a glacier- more snow accumulates in the winter than melts in the summer

a) As the wt. of the ice builds up the glacier will start to _______________.

2. All size sediments are _______________________ by a glacier.

a) All the particles are frozen to the bottom of the glacier & scrape along the bedrock leaving deep scratches called __________________or grooves

b) Smaller particles are also carried by the glacier as it scrapes & pushes the loose sediments

VALLEY MODIFICATION by glacial erosion, showing stages in the conversion of a meandering V-shaped valley into a straightened U-shaped valley.

1938

1981

1998

2005

Figure 10.41: These photographs of the Grinnell Glacier in Glacier National Park were taken over an almost 70 year period. The glacier is clearly visible and well developed in 1938. From 1981 through 2005, the amount of glacial ice has decreased and the melt water forming the lake has increased. In 2005, icebergs are further evidence of glacial melting.

II. Oceans & Costal Processes

A. Ocean Facts:

· Covers __________ of the earth’ surface

· Average depth of 4Km

· The deepest trench could submerge Mt. Everest w/another mile of ocean above it

· 1L of _______contains dissolved solids

B. Coastlines are shaped by waves & _____________ currents

1. Waves: water does not actually flow w/the wave it actually circulates in circles or ______________.

2. The wave is trasnferring energy that’s released on the shore when the wave breaks

3. The waves break when the depth of the water decreases & the bottom of the circulating __________ is slowed & the _________ continues @ the same speed.

4. Long shore currents are responsible for the characteristics features of ocean shorelines such as _____________ sands

a) ________________________: a deposit of sand will migrate w/the long shore currents.

b) Jetties: man’s attempt stop cont’d erosion of beaches:

· Long pile of large rocks extended out into the long shore current.

· Results in _________________ on the side from which the current is approaching but also causes an increase in erosion on the opposite side

III. Landscapes: the topography of the land (ESRT p.2)

A. Three Classifications:

1. Mountain Landscapes: greatest relief between the ___________ peaks & __________ valleys

2. Plateau Landscapes: relatively flat or rolling hills w/< relief that mountains & deep cut river valleys

3. Plain Landscapes: generally ___________ & @ _________ elevations.

1. 2. 3.

B. Landscapes are influenced by their _______________.

1. _______ climates = ________…the slopes are usually steeper.

2. Humid climates= wet…the slopes are __________________________ due to a protective cover of vegetation which decreases the erosion of weathered particles.

****

End for Unit Exam