Shaping Earth

7/29/2019 Shaping Earth

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Shaping Earths Surface


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Importance of Weathering

Participates in the rock cycle

Used in the formation of soils

Helps in the movement of rock material over the Earths

surface.


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ErosionWeathering breaks the rocks into fragments

Erosion then transports the material to new places of the

Earth

This is the physical process of removing the weathered

material.


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TransportationThe movement of eroded materials by rivers, glaciers,

wind, or waves.

As material is transported the weathering and erosionprocess continues


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This famous natural bridge is an example of a landformcreated by the sculpturing power of weathering and erosion.

It is Rainbow Bridge in the Rainbow Bridge NationalMonument Utah.


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The piles of rocks and

rock fragments arounda mass of solid rock is

evidence that the solid

rock is slowly

crumbling away. This

solid rock that is

crumbling to rock

fragments is in theGrand Canyon,

Arizona.


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Mechanical Weathering

The physical breaking of rock material without anychange to their chemical composition

Exfoliation

Spalling off layers of rock

Caused by reduced pressure on rocks as material isremoved from above.

Frost wedging

Caused as pores or cracks become filled with water

and then freeze and thaw. As the process repeats cracks and pores become larger

Eventually the rock will break off.


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(A)Frost wedging and (B) exfoliation are two examples of

mechanical weathering, or disintegration, of solid rock.


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Growing trees can break, separate, and move solid rock. (A)Note how this tree has raised the sidewalk. (B) This tree issurviving by growing roots into tiny joints and cracks,which become larger as the tree grows.


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Chemical Weathering

The alteration of materials by chemical reactions which

do change the chemical composition of the material.

Oxidation

When oxygen reacts with minerals in rocks

Carbonation A reaction between carbonic acid and minerals in

rocks

Hydration

A reaction between water and the minerals in rocks. Dissolves material

Water combines with the mineral to form a hydrate


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Limestone caves develop when slightly acidic groundwater

dissolves limestone along joints and bedding planes,carrying away rock components in solution. (A) Joints and

bedding planes in a limestone bluff. (B) This stream hascarried away less-resistant rock components, forming a cave

under the ledge.


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Soils

Soil is a mixture of unconsolidated weathered Earthmaterials and humus

Humus

Decayed organic matter

Bedrock

Solid rock below the soil

LoamA soil that is a mixture of sand, silt, and clay

Also referred to as topsoil


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Mass Movement

Criteria

Materialbedrock that has been weathered and eroded

debris that is carried away during the massmovement.

RateThe speed at which the movement occurs

Type

FallSlip

Slump

Slide

Flow


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Creep

The slow downhill movement of soil down a steep

slope

Fall

material moves in free fall down a cliff

Slip - materials moving together along a surface

Slump - Movement along a curved surface

Slide - Movement along a plane parallel to the surface.

FlowMass movement of a liquid


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The slow creep of soil is evidenced by the strange

growth pattern of these trees.


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Running Water

Stream Channels

Move materials in 3 ways.

As dissolved material in a solution

As materials carried in suspension

As sand and larger materials rolled, bounced, and

slid along with a stream

Most of the erosion that a stream does is done by the

larger material that moves along with it on the streambed.


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Moving streams of water

carry away dissolved

materials and sedimentsas they slowly erode the

land.


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Stream Erosion and Deposit Features

Floodplain

The wide, level floor of the valley adjacent to astream that has been built by the stream over time.

This is the area that the stream will begin to moveinto when moisture is high (flood).

A young stream usually has a v shaped flood plainwhereas a mature stream has a flattened floodplain.

Delta

Where the stream empties into an ocean or a lake itloses all of its sediment carrying ability

The sediments are deposited at the mouth of thestream and form a deposit


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A river usually stays in its channel, but during a flood itspills over and onto the adjacent flat land called the

floodplain.


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Three stages in the aging

and development of a

stream valley, (A) youth,(B) maturity, and (C) old

age.


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The waterfall and rapids

on the Yellowstone

River in Wyoming

indicate that the river is

actively down cutting.

Note the V-shapedcross-profile and lack of

floodplain,

characteristics of ayoung stream valley.


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(A)Delta of Nooksack River, Washington. Note thesediment-laden water, and how the land is being builtoutward by river sedimentation. (B) Cross section showinghow a small delta might form. Large deltas are more

complicated than this.


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GlaciersA mass of ice on land that moves under its ownweight.

Origin of Glaciers As snow melts and refreezes it is turned into ice.

After years of repeated thawing of snow andrefreezing into ice, the weight above begins to pack

down the ice below. The increased pressure drives out air and reforms the

ice into a crystalline structure of interlocking icecrystals with a very high mass

Alpine glaciers form in high elevations Valley glaciers form and flow downhill through a

valley

Continental glaciers cover large areas of a continent.


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Valley glacier on Mount Logan, Yukon Territory.


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Glacial Erosion and Deposition

A glacier erodes material by:

Bulldozing

Abrasion

Plucking

Material; that is deposited by a glacier forms a

moraine

Plucking material produces a depression called a

cirque As abrasion continues material becomes ground into

fine sediment called rock flour.


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(A)A stream-carved mountainside before glaciation.

(B) The same area after glaciation, with some of the

main features of mountain glaciation labeled.

Wind


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Wind

Wind Erosion and Transportation

Wind abrasion is the sandblasting process that occurs asmaterial is carried along with wind.

Deflation is the picking up of loose materials from theEarths surface.

Wind Deposits

DunesA low mound or ridge of material sediments

Form where the wind that is carrying the sedimentencounters some obstruction

LoessVery fine dust or silt that is deposited over large areas.

The source of the material is thought to be rock flourfrom glacier action


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Ventifact

formation

by

abrasion

from one

or severaldirections

.

Date post:	03-Apr-2018
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Shaping Earth

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