Weathering & Erosion - PowerPoint Presentation

Slide1

Weathering & ErosionSlide2

Earth’s Changing Surface

Earth is a constantly changing body affected by

natural forces

:

On the

Inside

:

Plate Tectonics

= moving of Earth’s Plates driven by

convection currents

Earthquakes & Volcanoes

On the

Outside

:

Weathering

&

ErosionSlide3

Weathering & Erosion

Weathering

is the process of

breaking down

or

dissolving

the earth’s rocks.

Mechanical

Weathering

Chemical

Weathering

Erosion

is the process of

moving

particles of rock from one locations to another.

Water

Glaciers

Wind

No rock is heard enough to resist the forces of weathering and erosion. Together they shape Earth’s

topography

.Slide4

Weathering

The interaction of the

lithosphere

(rock) with

the

atmosphere

(air) and

hydrosphere

(water) results

in

weathering

.

Driven by

climate

, combination of temperature and precipitation.

Hot & humid

=

greater

amount of weathering

Cool & Dry

=

reduced

amounts of weatheringSlide5

Physical Weathering

The type of weathering in which rock is

slowly

,

mechanically

broken down into

smaller

pieces.Changes the size and shape of the rock but not is composition

.

Factors:

Freezing and Thawing

Plant & Animal Actions

AbrasionsSlide6

Freezing and Thawing

In

colder

climates, water seeps into cracks and freezes.

The freezing water

expands

, making the crack

bigger – frost action.Slide7

Growth of Plants

As plants grow, their roots move into the cracks of rocks.

As roots grow, cracks become larger.

Roots grow into

c

racks and make

t

hem bigger.Slide8

Animal Actions

As animals

dig burrows

in the ground they loosen and break apart rocks in the soil.Slide9

Abrasion

Wind

,

water

and

ice

carry smaller sand and rock particles that act like

sandpaper on other rock surfaces.

Glacial Abrasion

Wind AbrasionSlide10

Chemical Weathering

The process of weathering that changes the rock’s

size

,

shape

AND

composition

.Produces rock particles that have a different mineral makeup from the rock that it came from.Agents:

Water

Oxygen

Carbon dioxide

Acid rainSlide11

Water

The

universal solvent

that dissolves substances,

solutes

, into solution.

As a rock is covered by water, minerals leave the rock by dissolving out.

Creates spaces in the rock that can weaken it and cause it to break apart.Slide12

Oxygen

Oxygen reacts easily with other substances changing their properties.

Oxygen (O) + Iron (Fe) = Iron oxide (Fe

2

O

3

), rustSlide13

Carbon Dioxide

Does not contribute to chemical weathering until dissolved in water.

Water (H

2

O) + Carbon Dioxide (CO

2

) = (H

2CO3) carbonic acid

Carbonic acid dissolves

calcite

,

f

ound in l

imestone

. Causes caves

a

nd caverns; Howe CavernsSlide14

Acid Rain

Acid rain comes mostly from the

burning of coal

by power plants in the Midwest.

Sulfur oxides rise into the air combining with water to form sulfuric acid.

Lowers the pH of water and bedrock killing off living organisms.

pH of lemon juiceSlide15
Slide16

Soil Formation

The formation of soil is a

slow and complex

process through the processes of

weathering

mixing with

organic matter

. Can be hundreds to thousands of years, 200-1200 years, in hard rock areas.Can takes less time, 20 years, in softer bedrock areas of shale and sandstone.Slide17

Soil Formation

Unweathered

Rock

Partially weathered

Rock

Partially weathered

Rock

Unweathered

Rock

Partially

weathered

Rock

Unweathered

Rock

Top Soil

Top Soil

Subsoil

Immature Soil

Mature SoilSlide18

Soil Horizons

Horizons:

O

Horizon –

organic material

Decayed plants and animals,

humus

A

Horizon –

topsoil

Humus, clay and minerals

B

Horizon –

subsoil

Clay but little humus

C

Horizon –

bedrock

Partly weathered rockSlide19

Soil Composition

Soil

– a mixture of rock particles (sand, silt and clay), minerals, decayed organic material (humus), air and water formed from

weathered rock

.Slide20

Soil Texture

Soil texture depends on the size of individual soil particles that make it up.

Gravel

– 2mm and larger

Sand

– less than 2mm

Silt

– less than 1/16mmClay - less than 1/256mmSlide21

Erosion

The

movement

of rock particles

from

one location to another,

Erosion

, in a downhill motion toward their lowest possible location; sea level.Agents of Erosion:

Water

Glaciers

WindSlide22

Erosion by Water

Water is always moving

downhill

due to the force of

gravity

.

The

greatest force of erosion.Wears down mountains to hillsCarves out valleysChanges the direction of river flow.Slide23

Erosion by Glaciers

Glaciers are formed from accumulated

snow

, compacted into

ice

and being pulled downhill by the force of

gravity

.Begin to form when snow reaches approximately 150ft in depth.Act as bulldozer

,

moving large amounts of rock and soil over time,

till

.

Material deposited after a glacier stops moving,

moraine

.Slide24
Slide25

Erosion by Wind

A major force of

physical

weathering, wind is also a contributor to

erosion

.

Creates

and transports rock particles.