Earth Science –Bennett HS—Q4 –Notebook

The following notes should be entered into your notebooks (a spiral notebook or loose leaf paper in a 3-ring binder), in chronological order and will be collected and graded during the last week of the marking period.. Blank lines and any information that appears in brackets “[xxxx]” is information that should have been entered by each student and will vary for each student.

--Ms. Milligan

4/18/2005

Weathering, Erosion & Deposition (WED)

Introduction

· weathering, erosion, and deposition are a main force behind landscape types

· But they are not the only reason for a plain, plateau, and mountain region to form

o Other factors such as glaciation and tectonic activity lead to landscape building

§ In New York State, glaciation is one of the main causes of many types of landscape regions

o the water cycle or hydrologic cycle (see graphic below) is the driving force behind WED (weathering, erosion, and deposition)

o winds also help form the surface landscape

o But without gravity and the sun this whole process would not occur

Water Cycle Diagram

[click here to see the diagram and copy it (including the labels) into your notes]

The water cycle process looks like this:

Evaporation Þ condensation Þ precipitation Þ infiltration Þ run-off

Without this process, weathering, erosion, and deposition would have a difficult time occurring on Earth.   

Weathering

-- chemical and physical processes that change the characteristics of rocks on the Earth’s surface.

o for weathering to occur, the rock sample must change and rock needs to be exposed to water and air

o Human processes such as pollution, (like acid rain) along with the acts of other living organisms, can cause chemical weathering to occur at faster rates. 

Weathering Process
The weathering process occurs when rocks are exposed to the hydrosphere (water) and atmosphere (air).

· These agents can change the physical and chemical characteristics of rocks.

· As rocks are broken down (weathered), they can be classified as different types of sediments, which are:

o boulders, cobbles, pebbles, sand, silt, clay, and colloids.

Fill in the following table using page 6 of the Earth Science Reference Tables, the graph that shows particle sizes:

Name of Particle

Minimum Diameter (cm)

Maximum Diameter (cm)

4/20/2005

Physical Weathering
-- when rocks are broken in to smaller pieces without changing the chemical composition of the rock.

· Think of a physical change (e.g., ripping a piece of paper) -- will change size, but all other characteristics will remain the same

· Types of physical weathering:

o Frost action/ice wedging -- breakup of rock caused by the freezing and thawing (contracting and expansion) of water. A very similar process occurs on roads, which causes potholes.

Frost Wedging Diagram

[click here to see the diagram and copy it (including the labels) into your notes]

o Abrasion --physical wearing down of rocks as they rub or bounce against each other--most common in windy areas, under glaciers, or in stream channels.

o Exfoliation --peeling away of large sheets of loosened materials at the surface of a rock. Common in shale, slate, and mica.

4/21/2005

Chemical Weathering
--when a rock is broken down by chemical action resulting in a change in the composition of a rock.

· Such as the change a piece of paper would go through after being burned.

· Main agents of chemical weathering are oxygen, rainwater, carbon dioxide, and acids produced by decaying plants and animals that leads to the formation of soil.

· There are a few types of chemical weathering such as:

o Oxidation -- when oxygen interacts chemically with minerals.

o Hydration -- when water interacts chemically with minerals.

o Carbonation -- when carbon dioxide interacts chemically with minerals.

What climatic conditions normally produce the greatest amount of chemical weathering and why?

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4/25/2005

Type Type

Changes

Examples

Weathering Rates

--depend on 3 different factors:

o Particle size/surface area exposed to the surface

--smaller particle sizes weathered faster

--larger exposed surface area weathered faster

o Mineral composition

o Climate –wet & warm climates increase weathering rates

Soil Formation

· One of the major products of weathering is soil

· Soil -- combination of particles of rocks, minerals, and organic matter

· Soil contains the necessary nutrients to support plant and animal life

· As a result of the weathering processes and biologic activity, soil horizons (layers) form

The below diagram is a mature soil profile common to New York State:

Soil Profile Diagram

[click here to see the diagram and copy it (including the labels) into your notes]

· Horizon O -- organic material on the upper most part of the profile (this layer is usually very thin)

· Horizon A -- commonly known as topsoil

o would probably include organic material (humus), such as fallen leaves, twigs, decaying plant and animal remains.

o helps prevent erosion, holds moisture, and decays to form a very rich soil known as humus.

· Horizon B -- the subsoil.

o usually will contain a fair amount of clay and iron oxides

· Horizon C --mostly of weatherized big rocks known as Parent material (the rock that the soil formed from)

· Horizon D -- is not shown in this illustration, usually contains solid bedrock.

4/26/2005

FACTORS THAT AFFECT THE WEATHERING RATE

4/27/2005

Erosion

Erosion refers to the transportation of rock, soil, and mineral particles.

· moving element.

· main driving force is gravity.

· Without gravity wind, running water, glaciers, waves, and rain would not occur.

Factors Affecting Transportation of Sediments

· Running water

· Factors affecting the movement of sediments in a stream:

o Gradient (slope)

o Discharge

o channel shape

· sediments rounded due to the grinding action, a process called abrasion

· The watershed of a stream is the area drained by a stream and its tributaries (smaller feeder streams).

· The average velocity (speed) of a stream depends on its slope and discharge, which in turn can explain the carrying power of a stream.

4/28/2005

Fill in the following table using page 6 of the Earth Science Reference Tables, the graph that shows the relationship between stream velocity and particle size transport:

Stream Velocity (cm/sec)	Maximum Diameter (cm) transported	Name of largest Particle moved
25
75
100
250
400
600

· Meanders (see diagram below)

o Deposits-velocity is lowest along the inner banks

o Along a straight channel segment, fastest in mid-channel, near the surface.

o Erosion-around a bend, the zone of high velocity swings to the outside of the channel.

o another landform -- an oxbow lake -- can develop-- forming an independent loop that will become a lake

Oxbow Lake Formation Diagram

[click here to see the diagram and copy it (including the labels) into your notes]

Valleys Eroded by Streams and Glaciers

· Valleys that have been eroded:

o by streams are v-shaped

o by glaciers are u-shaped

Effect of Humans on Erosion
Humans add greatly to the natural processes of land erosion through activities, such as:

· highway and construction,

· destruction of forests (clear-cutting),

·