Name: ___________________________________________ Regents Earth Science

EROSION AND DEPOSITION

Erosion- Process by which sediments are picked up and transported away

Deposition- Process by which rock and or sediment are dropped from an erosional

system

I- Glacial Erosion and Deposition

1.Types of Glaciers

A. ALPINE- Confined to mountains and high elevations. Glaciers carve out "U-

shaped" valleys in mountainous regions.

B. CONTINENTAL- Formed when the

average global

temperature decreases

and the winter snow

no longer melt during

the warmer seasons.

As many years of

snowfall build up and

are compressed, it

recrystallizes into

glacial ice. At this

point the ice begins to

flow from its place of

origin. (pulled

downhill by gravity)

2. Glacial Erosion- Glaciers transport rock and sediment in 3 ways:

1. Within the ice

2. On top of the ice

3. In front of the ice

3. Glacial Deposition- All of the sediments being carried by the glacier are slowly being

transported to the glaciers front. (This is where they are deposited)

Deposition Page 2 4. Glacial Deposits and Features

A. Terminal Moraine- Unsorted glacial

deposit found along the

leading edge of the

glacier. Unsorted

glacial deposits are

called Glacial Till.

B. Glacial Erratic- Rocks carried within the glacier that are left behind when the

glacier melts.

C. Glacial Striations- Many glacial erratics will have scratches and striations on their

surface due to being scraped along the bedrock as the glacier

advanced. The bedrock will also have striations. This can assist

scientists in determining the direction the glacier was moving.

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D. Drumlins- Streamline hills of unsorted

sediments that can also be used

to determine the direction a

glacier has moved.

E. The Finger Lakes- These lakes which

are located in western

New York state, (see

NYS Earth Science

Reference Tables Page

3) were created as the

advancing ice sheet

deeply scoured

(eroded) former north-

south river valleys.

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F. Formation of a Kettle Hole Lake (Lake Ronkonkoma is a Kettle Hole Lake)

At the front of a glacier, large pieces of ice

often break off as the glacier melts back

As the glacier melts back, outwash covers

the fallen block of ice

The outwash insulates the ice and

prevents it from melting for a long period

of time

When the block of ice melts the outwash

fills in where the ice was-Forming a kettle

hole

Some kettle holes fill with water forming a

kettle hole lakes

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II- Erosion and Landscape Development

Landscape- A portion of the Earth’s surface visible from any given point on the land or from

space. Landscapes can be directly observed, viewed from photographs or

interpreted from topographic (contour) maps.

Landscape development is caused by the interaction between uplifting forces (mounting

building) and leveling forces (Weathering and erosion). The

dominant force will determine whether a landscape will be uplifted

or leveled.

A. The effects of Climate on Landscape Development

Climate is the average Temperature and Moisture conditions of a region over a period of time.

1. Arid Climate- Landscapes that have

developed under arid

conditions (Warm and

dry) are characterized by

steep slopes and angular

features.

2. Humid Climate- Landscapes that have

developed under humid

conditions (warm and

moist) are

characterized by gently

rolling vegetated slopes

and smooth features.

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B. The effects of Bedrock on Landscape Development

Bedrock is the solid unweathered portion of the earth’s crust.

1. Landscapes with similar characteristics can be grouped into distinctive

regions. These regions are based on the type and underlying rock structure.

The major landscape groups are mountains, plateaus, and plains.

2. The boundaries between landscape regions are well defined by surface

features. Those landscape regions with similar characteristics are called

physiographic provinces. New York State has a wide variety of landscape

regions, they can be seen on page 2 of the N.Y.S. Earth Science Reference

Tables.

C. The effects of Rock Structure on Stream drainage Patterns

1. Streams can be identified and grouped by patterns. The area drained by a

stream or system of streams is called a drainage basin.

2. Patterns formed by streams in a drainage basin are called stream drainage

patterns. Stream patterns are determined by the type, and structure of

rock over which the streams flow, and by how long they have been flowing.

3. Stream drainage patterns are easily identified on topographic maps.

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DEPOSITION

Deposition- Process by which rock and or sediment is dropped from an erosional

system

II- Factors affecting Deposition Rate

** Deposition is usually caused by a decrease in velocity of the transporting system

A. Size- Larger sediments settle faster than small ones, since larger sediments weigh more

then smaller ones. (Colloids may remain suspended for years because they are

very light weight)

B. Density- The greater the Density of a particle, the faster it will settle. If you have 2

particles of equal size (volume) the more dense one will weigh more, therefore it

can overcome the resistance of the water easier.

C. Shape- The more spherical an object the faster it will settle. The flatter object has a

greater amount of resistance with the water.

III- Sorting of Sediment

A. Graded Bedding

1- Horizontal layer or bed of sediment with larger, heavier particles at the bottom and

grading upward to the smallest on top.

2- Usually results from rapid deposition (Often associated with density or turbidity

currents)

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B. Horizontal Bedding

1-As a streams velocity decreases (such as when it enters a body of still water )

the larger, heavier particles settle out first, nearest the shore.

2- Sediment size and density decrease as you move further out into the body of still

water.

3- Precipitation of dissolved materials is the last to be deposited (Limestone, Salts,

Gypsum)

4- Forms a Delta when deposition takes place into a body of water, and an Alluvial

Fan when deposition takes place on land. (usually at the base of a mountain or

hill)

C. Unsorted

1- Usually caused by glaciers.

2. There is no fluid medium to sort the sediments.

3- Random distribution of sediment sizes with no bedding or layering.

4- Long Islands north shore beaches are a perfect example.

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IV- Characteristics of an Erosional-Depositional System

A. Changes in Energy

1- Potential Energy and Kinetic Energy both decrease in a stream as it flows downhill

(Kinetic Energy is lost due to friction with the stream bed), therefore there is a net

loss of energy between the source and the mouth.

2-.Erosion is greatest on steep slopes where the Kinetic Energy is greatest (Fast

Stream)

3- Deposition is greatest on gentle slopes where Kinetic Energy is lowest (Slow

Stream)

B. Equilibrium

1- Everything is in a state of dynamic equilibrium. Anything eroded must be

deposited.

2- Rate of Erosion = Rate of Deposition in the system as a whole.

Diagram: Characteristics of an Erosional-Depositional System