Any comments????Any comments????

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CHAPTER 3CHAPTER 3Weathering Weathering and Erosionand Erosion

FIRST YEAR GEOG MS CLIFFORD St Tiernans CS

Where in the world is Where in the world is this???this???

And this?And this?

How about this?How about this?• Any particular type of rock???• From what family does it belong?

What or where is this?What or where is this?

Denudation Denudation

• This topic attempts to show how effective nature is at shaping the world around us. The physical landscape around us is very varied and in certain places it can be very beautiful and spectacular.

• When we look at or visit the "Grand Canyon", "Niagra Falls", the "Giant's Causeway" or the "Cliffs of Moher" we realise and appreciate this.

• Denudation is the term used to describe the constant on-going wearing down of the Earth's surface by Erosion, Weathering.

Denudation Denudation is the wearing is the wearing

away of the rocks on the away of the rocks on the

earths surfaceearths surfaceDenudation occurs through 2 processes-1. Weathering 2. Erosion

Weathering: What is weathering?• This is the break down and decay of rocks that are exposed on

the earths surface to the weather• Weathering takes place on site and material is not moved

away

Erosion: What is erosion?• Breaking up of Rocks and removal of the rocks• Erosion is caused by: moving water, ice and air• Material that has been broken down is transported away and

dumped somewhere else

• DENUDATION=EROSION + WEATHERING

There are 2 types of weathering: mechanical and There are 2 types of weathering: mechanical and

chemicalchemical

(1)MECHANICAL WEATHERING(1)MECHANICAL WEATHERING• THIS OCCURS WHEN ROCKS ARE BROKEN DOWN

INTO SMALLER PIECES. • THIS IS CAUSED BY• 1. FROST• 2. SUDDEN CHANGES IN TEMPERATURES OR

EXTREME TEMPERATURE CHANGES

MECHANICAL MECHANICAL WEATHERINGWEATHERING

• MECHANICAL WEATHERING OCCURS WHEN ROCKS ARE DISSOLVED BECAUSE OF A CHEMICAL CHANGE

• THIS IS USUALLY CAUSED BY WATER-RAIN

QUICK ACTIVITYQUICK ACTIVITY• WHAT IS MEANT BY THE TERM “DENUDATION” ?

• WHAT DO THE FOLLOWING TERMS MEAN• (A) WEATHERING• (B) EROSION

• NAME THE 2 TYPES OF WEATHERING• NAME THE AGENTS THAT CAUSE EROSION• NAME 2 DIFFERENCES BETWEEN WEATHERING

AND EROSION

MECHANICAL MECHANICAL WEATHERINGWEATHERING

• NOW WE ARE GOING TO LOOK AT MECHANICAL WEATHERING:

• THERE ARE 2 TYPES OF MECHANICAL WEATHERING

1. Weathering. There are 3 1. Weathering. There are 3

types of mechanical types of mechanical

weatheringweathering

3 TYPES OFMechanical weathering

1.Freeze thaw action3. Crystallisation

of salts2. Onion peeling

exfoliation

Mechanical weathering:Mechanical weathering:

1. Freeze Thaw Action 1. Freeze Thaw Action

(this occurs in upland areas)(this occurs in upland areas)

• Freeze-Thaw Action

• During the day, water gathers in the cracks of rocks high up a mountain or in cold areas around the world. THIS WATER COMES FROM RAIN

• At night as temperatures drop, water freezes. it expands by 10% and as a result it exerts pressure on the surrounding rock. Over a period of time the rock breaks apart.

• Freeze- Thaw Action results in the accumulation of lots of small rocks known as "Scree“ gathering at the bottom on the slope.

Mechanical Mechanical weatheringweathering

2.Exfoliation 2.Exfoliation (Onion (Onion

Peeling)Peeling)Onion Peeling

This process, also known as "Exfoliation", occurs in desert areas where there is a huge difference between the daytime and night time temperatures.

The outer layer of the rock expands during the day due to the intense heat and contracts at night due to the extreme cold. This constant expansion and contraction weakens the rock and causes the outer layer to break away from the rock.

SUMMARYSUMMARY• FREEZE THAW ACTION OCCURS IN UPLAND

AREAS• IT SHATTERS THE ROCKS INTO SMALLER PIECES

CALLED SCREE• THE SCREE GATHERS AT THE BOTTOM OF THE

MOUNTAIN (AT THE FOOT OF THE SLOPES)

QUESTIONSQUESTIONS• What does freeze thaw action mean?• What does scree mean?• Draw a diagram to show how freeze thaw action

occurs

Chemical weatheringChemical weathering• CARBONATION IS A TYPE OF CHEMICAL WEATHERING THAT WE

WILL STUDY

• WHEN RAIN FALLS, IT TAKES IN CARBON DIOXIDE FROM THE ATMOSPHERE

• THE CARBON DIOXIDE MIXES WITH THE RAIN TO FORM CARBONIC ACID

• LIMESTONE ROCK CONTAINS CALCIUM CARBONATE (FROM ANIMAL BONES).

• WHEN THE ACID RAIN FALLS ON THE LIMESTONE, THE CARBONIC ACID REACTS WITH THE CALCIUM CARBONATE AND THE LIMESTONE IS DISSOLVED

• THERE ARE A LOT OF CRACKS IN LIMESTONE SO THIS MAKES IT EASY FOR THE RAIN TO PASS THROUGH IT

THE BURREN IN CO. CLARETHE BURREN IN CO. CLARE

ii

karst Region in Co Clare: The Burrenkarst Region in Co Clare: The Burren

Limestone pavementLimestone pavement

When rain seeps through the rock, it weathers it by carbonationThe cracks are widened to from grikesThe remaining rock is called clints

Swallow hole Swallow hole

Underground caves in the Underground caves in the BurrenBurren

SWALLOW HOLESSWALLOW HOLESTHE CARBONIC ACID IN RAIN DISSOLVES THE LIMESTONE.OVER TIME THE GRIKES (NOT YIKES) BECOME ENLARGED TO FORM SWALLOW HOLES

WHEN THE RAINWATER DISAPPEARS UNDERGROUND, THE LIMESTONE IS DISSOLVED TO FORM LARGE CAVES

STALACTITES AND STALAGMITESSTALACTITES AND STALAGMITES• STALACTITES• DROPS OF WATER CONTAINING DISSOLFGVED LIMESTONE

(CALCIUM CARBONATE) SEEP THROUGH THE ROCK

• SOME OF THESE HANG FROM THE ROOF OF THE CAVE.

• IF THE WATER EVAPORATES, IT LEAVES THE CALCITE BEHIND ON THE ROOF

• THESE GROW DOWN OVER THE YEARS TO FORM STALACTITES (HANG ON TITE)

• STALAGMITES• IF THE DROPS OF WATER ON THE ROOF FALL TO THE

FLOOR, THE WATER EVAPORATES LEAVING BEHIND CALCITE ON THE GROUND. OVER TIME THESE GROW TO FORM COLUMS CALLED STALAGMITES

Underground cave with stalactites and Underground cave with stalactites and

stalagmitesstalagmites

Stalactites stalagmites and Stalactites stalagmites and

columnscolumns

THE BURREN, CO CLARETHE BURREN, CO CLARE• THE BURREN IS ONE OF IRELANDS MOST IMPORTANT

TOURIST DESTINATIONS.• IT HAS A WIDE RANGE OF ATTRACTIONS FOR TOURISTS

• LIST 4 OF ITS MAIN ATTRACTIONS (PAGE 30)

• WHAT ARE 4 BENEFITS OF TOURISM IN THE BURREN?

• WHAT ARE 4 DISADVANTAGES OF TOURISM IN THE BURREN?

GG