Water Shapes the Land - PowerPoint Presentation

Slide1

Water Shapes the Land

J. Quigley

4/2012Slide2

Water Shapes the LandSlide3

Water Shapes the Land

The Mississippi River is like a thousand dump trucks… every year it carries more than 300 million tons of sediment to the ocean!

This sediment is being washed away from the surface of the land and is called erosion.Slide4

Water Shapes the Land

The primary force of erosion is

gravity.

Gravity pulls sediment and water

downhill

The end result of erosion is the deposition of

sediment

Deposition is the process in which sediment is laid down in new locationsSlide5

Water Shapes the Land

Most sediment is moved and deposited by

flowing water.

Flowing water is the major agent of

erosion

responsible for shaping Earth’s surfaceSlide6

Running Water Erodes the Land

Water from rain or melted snow may soak into the ground, evaporate or flow over the surface as

runoff

.

Erosion begins when runoff carries small particles of soil

downhill

.

Runoff turns into streams, which turn into rivers… each larger body of water carries more sediment and does more erosion and

depositionSlide7

Running Water Erodes the Land

Streams and rivers erode larger particles of sediment by

saltation

.

Saltation is the process of particles bouncing along a

stream bottom

.

During floods, a fast moving river can move boulders the size of a small car!!

This breaks down the

rocks

into sediment.Slide8

Running Water Erodes the Land

A stream’s ability to erode depends mainly on its s

peed

.

Faster streams carry more sediment than slow streams of

equal size

Fast streams can also carry larger sized sediment than a

slower

streamSlide9

Features Formed by Water Erosion

Water erosion forms:

V-shaped valleys

Waterfalls

Flood plains

Meanders

Oxbow lakesSlide10

Features Formed by Water Erosion

V-shaped valley-

near a stream’s source, the stream flows fast as it plunges down steep slopes. The stream erodes the rock on both sides making the valley even steeper

They often contain rapids and

waterfallsSlide11

Features Formed by Water Erosion

Waterfall

- A water fall develops where a stream crosses rock layers that differ in hardness. The harder layers resist

erosion

, forming the top of the waterfall. The softer rock layers are worn away, leaving a

cliff

over which the waterfall tumbles.Slide12

Features Formed by Water Erosion

FLOOD PLAIN

-Where a river or stream crosses gently sloping land, a flood plain forms.

As a river flows across a flood plain, it deposits sediment

The sediment builds up into long, low ridges called natural

levees

These levees prevent the river from spilling over the banks and make a

channel

for the riverSlide13

Flood plainSlide14

Features Formed by Water Erosion

MEANDERS

-

Where a river curves slightly, the water on the outside of the curve moves more rapidly than water on the inside.

Fast moving

water causes more erosion, there fore the river tends to remove more soil from the outside of the curve

Sediment is deposited on the

inside

of the curve… over time, this process forms a loop like bend in the river called a meander. Slide15

MeanderSlide16

Features Formed by Water Erosion

Oxbow lake-

Sometimes during a flood, a river erodes through a narrow meander and forms a new path. Sediments build up and cut off the old meander creating a separate,

curved lake

. Slide17

Features Formed by Water Deposition

As a stream or river

slows down

, it begins to deposit sediment.

Features deposited by flowing water include

alluvial fans

and

deltas

. Slide18

Features Formed by Water Deposition

As a stream flows out of a mountain and onto the plains, it slows down and

sediment settles out.

The result is a

fan-shaped deposit of sediment on land

called an alluvial fanSlide19

Features Formed by Water Deposition

When a stream flows into a

lake or ocean

, the water slows down.

The sediment that the stream was carrying is deposited in the form of a delta

A delta is a mass of sediment deposited where a

river enters a large body of water Slide20

Groundwater Erosion

The process of

chemical weathering

causes much groundwater erosion, including the formation of caves, stalactites, stalagmites and sinkholes.Slide21

Groundwater Erosion

As CO

2

in the air combines with rainwater it makes

acid rain

. The acid rain erodes limestone making

caves

and cavernsSlide22

Groundwater Erosion

Sometimes water drips into the cavern or cave from the rock layers above carrying

minerals

.

Where the water drips from the cavern ceiling, a

stalactite

is formed. Slide23

Groundwater Erosion

If the water drips down to the

floor,

a pillar of minerals called a

stalagmite

is formed.Slide24

Groundwater Erosion

If erosion weakens a layer of limestone, entire portions of the ground can suddenly collapse resulting in a

sinkhole.Slide25

Glaciers and Wind

Glaciers

form in places where more snow falls than melts

or

sublimates.

As the

layers of snow pile up, the weight on the underlying snow increases, eventually turning the

snow

into ice or a glacierSlide26

Glaciers

Even though glaciers appear to be stationary, they are actually

moving

!

The force of gravity pulls the ice

down hill

, the ice flows very slowly.Slide27

Glaciers

There are two types of glaciers:

Continental

glaciers

Valley

glaciersSlide28

Glaciers

Continental Glacier-

thick sheet

of ice that covers a huge area, such as a continent or large island.

Most of earth’s fresh water is frozen in the continental glaciers that cover

Antarctica

and GreenlandSlide29

Glaciers

Valley Glacier- Occur high in a

high mountain valley

A valley glacier usually begins near a

mountain peak

and winds down through a valley formed originally by a streamSlide30

Glacial Erosion and Deposition

Glaciers are very effective at

eroding rock

.

Glaciers erode rock through abrasion and

plucking

.

Plucking is when glacier ice widens cracks in bedrock beneath the glacier, and those pieces are frozen and

stuck to the glacier. As the glacier moves, the rocks get “plucked” out of the ground and pulled down

with the glacierSlide31

Features formed by glacial erosion

Glaciers cause many distinctive features in the landscape, including:

Cirques

Horns

U-shaped valleys

Glacial lakesSlide32

Features formed by glacial erosion

Cirque-

a large bowl shaped valley in the mountain side caused by a glacier. They look like they were made with a giant ice cream scoop. Slide33

Features formed by glacial erosion

Horns- If several cirques form close together, a

ridge

my be left between them, if several ridges connect to form a pyramid-shaped peak. The

sharp peak

is called a horn.

The peaks of the Swiss Alps were made by glaciersSlide34

Features formed by glacial erosion

U-Shaped Valley-

Glaciers widen and deepen existing valleys. When a glacier flows through a V-shaped valley it carves out the rocks through plucking and abrasion, making it a U shape insteadSlide35

Features formed by glacial erosion

Glacial lake- Continental glaciers can enlarge and

deepen

natural depressions in the ground. These depressions then fill with water when the glaciers retreat.

The

Great Lakes

in the USA are glacial lakes. Slide36

Features formed by glacial deposition

A glacier gathers and transports a huge amount of

rock and soil

as it moves.

When a glacier melts, it deposits its load of sediment, creating a variety of

landforms

.Slide37

Features formed by glacial deposition

Glacial sediment is called

till

.

Till is an unsorted mixture of

sediment

containing fragments of many sizes.

Giant boulders, gravel,

sand and rock dust are all found in tillGlaciers

deposit till as they meltSlide38

Features formed by glacial deposition

Moraines

form from till.

A moraine is a

mound of sediment

at the downhill end of a glacier and along its sides. Slide39

Wind Erosion and Deposition

Wind can also cause

erosion

and deposition

The

speed

of the wind determines the size of the materials it carries.

Slow

wind carry only small particles, while fast winds can move large boulders!Slide40

Wind Erosion and Deposition

Wind erodes the land by deflation and

abrasion

.

Deflation

occurs when wind picks up and carries away loose surface materials.Slide41

Wind Erosion and Deposition

Dry regions where winds are

strong

, sand and dust are lifted from the surface and

carried away

.

Over time, the surface of the ground is lowered, larger

rocks

are left behind, forming a rocky surface that covers much of the land in dry regionsSlide42

Wind Erosion and Deposition

Abrasion is a form of

mechanical weathering

.

Abrasion by wind occurs in much the same way as abrasion in flowing water.

Wind

blows

sand against other rocks slowly sandblasting them away and removing the weathered particlesSlide43

Effects of Wind Deposition

When wind

slows down

it drops the sediment it is carrying.

Features deposited by wind include sand

dunes

and

loess

depositsSlide44

Wind Erosion and Deposition

Deposits formed from windblown sand are called

dunes.Slide45

Wind Erosion and Deposition

Deposits formed from windblown dust are called

loess

.

Loess

consists mainly of finely ground particles. Slide46

The Restless Ocean

Oceans surround all of the continents

Earth’s ocean waters are divided into four major oceans:

The Pacific

Atlantic

Indian

Arctic

These oceans also include smaller bodies of water such as

seas and gulfs.Slide47

Exploring the OceanSlide48

Exploring the Ocean

Most of Earth’s water is exists as

salt water

in the oceans.

Ocean water is a mixture that includes dissolved

salts and gases

Salinity

is the proportion of dissolved salts in water.

On average there are about 35 grams of dissolved salts in each kilogram of ocean water. Slide49

Exploring the Ocean

Salt is added to the oceans by

rivers and volcanoes.

Rain slowly dissolves salts out of surface rocks

All the salts get deposited in the oceans, making them “

salt water

”Slide50

Changes with Depth

Conditions in the ocean, such as the amount of

sunlight

, temperature and

pressure

change as you move from the surface to the ocean floor.

Light and temperature

decrease

with depth, and pressure increasesSlide51

Exploring the Ocean

Sunlight decreases with depth. The

deep ocean

is totally dark

Light cannot penetrate deeper than

200 metersSlide52

Exploring the Ocean

Water temperature decreases with depth.

The top

100 to 500

meters of the ocean are well mixed and relatively warm.

Deeper water is much

colder and denser

. Deep water moves very slowly and does not interact much with the surface layerSlide53

Exploring the Ocean

Pressure

increases continuously with depth in the ocean.

At a depth of

500 meters

, the pressure is about

50 times

greater than the atmospheric pressure at sea level.

Few forms of life can tolerate such great pressuresSlide54

Exploring the ocean

At the

coast line

, there are reefs and shallow waters called the continental shelf…

At the edge of the

continental shelf,

the continental slope descends steeply to the floor of the deep oceanSlide55

Exploring the Ocean

The

ocean floor-

is a vast, flat plain dotted with volcanic peaks.

It also contains the

mid ocean ridges

.

There are also basins and

trenches along the edges of some oceanic platesSlide56

Exploring the Ocean

Mariana Trench

is the deepest place on earth, 11 kilometers below sea level!!!

Overall, the average depth of the ocean is about

3.8 meters

to the floor!Slide57

Ocean Currents

Currents

are the patterns of the oceans.

Ocean Currents are affected by

winds

, earth’s rotation and the position and shapes of the

continents.Slide58

Ocean Currents

Surface currents-

A surface current is a large stream of ocean water that moves continuously in about the same path

Winds blowing

across the surface of the ocean cause the continuous flows of surface currentsSlide59

Ocean Currents

Unlike surface currents,

deep currents

are not caused by winds

Deep ocean currents are caused by differences in the

density

of the ocean water

Denser water results from

colder temperature or high salinity

Because deep ocean currents are affected by density, they are called

density currentsSlide60

Ocean Currents

Density currents are responsible for a

slow mixing

of the water between the surface and deeper ocean.Slide61

Ocean Currents

In certain places in the oceans, water from the deep oceans moves

upward

toward the surface. The movement of water from the deep ocean to the surface is called

upwelling

.Slide62

Ocean Currents

In upwelling, winds blow

warm

surface water aside, this allows

cold

water from the deep ocean to rise and take the place of the warmer water.

This is important for mixing

oxygen and nutrients

in the oceanSlide63

Wave Erosion and Deposition

Two physical processes, hydraulic

action

and

abrasion

are responsible for wave erosion

Over time, wave erosion and deposition work together to straighten a

coast lineSlide64

Wave Erosion

In the process of hydraulic action occurs when

waves

pound on cracks in rocks. As water forces its way into the cracks, rocks break off.

The rock pieces are then turned to

sediment

through abrasionSlide65

Wave Erosion

Sand

is continuously eroded and deposited along the shore by waves and currents

Longshore

drift

is the process that moves sand along the shore.

As waves break, they carry sand up the beach at an

angle.

This angled sand is longshore drift.Slide66

Deposition by currents and waves

Sediments in the ocean are eventually pushed up on land and create

beaches