OB J ECTI VES:

1. TO R EVI EW TE RM S I NTR ODU CED DU RI NG YE STERD AY ’S LESSO N – DEN UDATI ON, WEATHER IN G, ER OSI ON, A ND F RE EZE- THAW AC TI ON.

2. TO I NT ROD UCE STU DENT S TO CH EMI CA L WEATHER IN G.

1A2 Geography14th April, 2015

Homework

Let’s take a look at last night’s homework assignment.What answers did you give in response to questions 1&

2, page 103?

During yesterday’s lesson…

We learned about:

i. Denudation.

ii. Erosion.

iii. Weathering.

iv. Freeze-thaw action – what kind of weathering is this an example of?

What are the key differences between these processes?

Review

1. Denudation is the term used to describe the collection of processes that wear away the rock and soil of Earth’s crust.

2. Erosion refers to the breakdown of rock and the removal of rock particles. (Caused by moving air, moving water and moving ice.)

3. Weathering refers to the breakdown of rock in areas where it is exposed to the weather. Two categories of weathering – mechanical and chemical. Weathered rock is not transported. It accumulates on site to form scree.

Chemical Weathering

Chemical weathering takes place when rocks are dissolved due to a chemical reaction.

One example of chemical weathering is carbonation.

Carbonation

We depend on fossil fuels in our daily lives, but their use has the potential to damage the environment.

Fossil fuels provide energy for industry, power millions of cars around the globe, and provide heat for homes.

The burning of fossil fuels for these purposes is leading to the release of a large amount of carbon dioxide (a greenhouse gas) into the atmosphere.

Carbonation occurs when water vapour in the air combines with this gas.

Carbonation

As rain forms in the atmosphere, it combines with the carbon dioxide to form a relatively weak carbonic acid.

Although this carbonic acid is weak, it can make a significant impact on rock, particularly limestone.

Limestone contains 80% calcium carbonate (a white mineral). The acid reacts with this, causing the rock to dissolve.

As limestone is permeable, rainwater can pass down through it.

Rain water mixing with carbon dioxide.

Effects of carbonation

Carbonation

Carbonation: Karst Landscape

Carbonation occurs in areas where bare limestone rock is exposed to the weather.

These regions are known as karst landscapes, named after a limestone region in Slovenia called Karst.

There is an example of a karst landscape in Ireland, the Burren, Co. Clare (we’ll be learning more about this place on Tuesday 21st).

Carbonation: Karst Landscape

Limestone rock was exposed here millennia ago when enormous glaciers stripped the landscape of its soil covering.

Carbonation has created a unique landscape here, resulting in the development of landforms on the surface and underground.