Surface - PowerPoint Presentation

Slide1

Surface processes

Bilingual biology and geology 3º ESOMª Eugenia Alba TorreiroSlide2

How the Earth’s surface changes

Exogenous geological process:

The Earth’s surface is continually being changed and shaped by different

exogenous geological agents as temperature, humidity, wind, precipitation, streams and rivers, ice, seas, etc.

When these agents work on rocks of the Earth’s surface they carry out what are called exogenous geological processes: Erosion

TransportationSedimentation (deposition)

Erosion, Transportation, Sedimentation.Slide3

Exogenous geological processesSlide4

Weathering

Weathering is the processes of fragmentation

and alteration of rocks by the joint action of the atmosphere, water and living things.

The weathering take place in two ways:Physical weathering takes place when solid rocks are

fragmented by physical processes that do not change its chemical composition.Chemical weathering takes place when minerals in rocks are chemically altered or

dissolved.

SOILWhen rocks on the Earth’s surface are weathered, they eventually produce soil. Soil formation is a very slow process which can last thousands of years.Slide5

Types of weatheringSlide6

SoilSlide7

Streams and riversSlide8

TorrentsSlide9

Permanent streams and rivers

They are continuous currents of water which run along a fixed channel in a

valley. They are formed by rainwater, springs or melting ice and have three stages: upper course, middle course and lower course.Slide10

The stages of the rivers

Upper course

The river is closest to its source.

It usually runs down a steep slope and the water flows quickly.

There is a lot of erosion and little sedimentation. The

river valley is often narrow and V-shaped with frequent

rapids and waterfalls. Gorges and

canyons

are features of this stage. Slide11

Middle course

Middle course The slope is much shallower. The water flows more

slowly: heavier materials are deposited but erosion and transportation of lighter materials continues. Their features are:

V-shaped river valley but the slopes are less steep and the bottom is flat. The deposited sediment creates floodplains.

Meandres which are large bends in the river on flat terrain. Fluvial terraces

which are the remains of old floodplains when the river flowed at a higher elevationSlide12

Lower course

It is the last stage of the river.

The slope is minimal and the water flows slowly.

Meanders are large and the river valley is very wide

with large floodplains. Materials are deposited as

sediments. In the river mouth, the accumulation of sediment forms deltas

. If the deltas are washes away an estuary is formed.Slide13

Karst topography

Karst is a landscape where the rocks on the Earth’s surface, usually

limestone or dolomite, has been dissolved by groundwater, forming an

irregular surface.Slide14
Slide15

Karst topography

Surface featuresLimestone pavements, flat surfaces crossed by many fissures.

Sinkholes, depressions in the ground.Canyons, deep channels with vertical walls.

Underground features

Caves, tunnels and galleries in the rock.Stalactites, pointed columns descending from the roof.

Stalagmites, pointed columns ascending from the floor.Columns, when a stalactite and stalagmite join together.Slide16
Slide17
Slide18

The sea

Action of waves.

Waves

break off fragments of rock and

throw them against the coast as projectiles, increasing the erosive power of the water. This process is known marine abrasion.

Action of tides. The

rise and fall of the sea level is capable of

transporting

abundant loose materials.

Action of currents.

Coastal currents, which run parallel to the coast, are capable of

transporting

large amounts of

sand

and

small stones

.Slide19

Erosive coastal features

Cliffs

, high and rough walls of rock formed by marine erosion due to waves breaking at their feet.

Abrasion platform,

a flat area at the bottom of cliffs formed by erosion of the cliffs.

Caves, natural arches

and

stacks,

are the result of different rocks which have

different resistance to erosion

.

Rocky coastsSlide20

Transportation and sedimentary coastal features

Beach

Sand bank

Marshes

Beaches

are formed by the accumulation of

gravel

and

sand

on the

shore

.

Barrier island

are deposits of sand (

sandbank

) parallel to the coast.

Tombolos

are sand banks or spits which attach small island to the coast.

Sand spits

are long deposits of

sands

and

gravels

attached to the coast and formed by the

longshore

drift

.

Lagoons

are areas of water formed when sandbanks close off a bay or a gulf.

Marshes

are a kind of

wetland

formed at the mouths of rivers by the action of the

tides

.Slide21

Sand bank

and

spit

Tombolo

Beach

Marshes

Flat-coastsSlide22

Glaciers

A

glacier is an enormous mass of permanent ice that forms in cold regions

. It moves slowly downhill, with strong erosive power, shaping the landscape.There are two types of glaciers: ice sheets or polar glaciers and

valley glaciers.Slide23

Alpine glacier

Ice sheet

14 million km

2

30 million km

3

of ice

Antarctica

Greenland

1,7 million km

2

2 million km

3

of ice

An

ice sheet

is a mass that covers more than 50 000 km

2

of land area.

The two types of glaciersSlide24

The cirque

The

accumulation zone

is the highest part of the glacier.

The snow accumulates, is compacted and slowly transforms into

ice. The glacier erodes the land into an amphitheatre-shaped valley

called cirque.

Tarn

(lake)

It is a mountain lake formed in the cirque when the ice

melts

.Slide25

The tongue

The

slipping zone includes one or more tongues of ice which slide slowly downhill creating a U-shaped valley. The materials eroded and transported by the ice forms deposits called

moraines.

The

glacier terminus is the bottom of the glacier. Here, the ice breaks and melts

and deposits the transported materials. These materials form terminal moraines.Slide26

The wind

The action of the wind is predominant in arid regions where precipitation is low and vegetation almost non-existent: deserts, semi deserts and beaches. Slide27

Deflation

. The removal of loose materials from the ground.

Dunes

Natural arch

Alveolar

erostion