1. Gradation Biotic and Chemical Weathering
Geography 12
Ms. Inden

2. Biotic Weathering
Plant roots work their way into cracks and force rocks to break apart
Some chemical reactions take place as well – chemical weathering
Animals burrow into ground
Human mining activity
Please note: Sometimes referred to as biological weathering. However, biological weathering refers at times to the chemical reactions used to create soils (chelating) from biotic weathering

3. Chemical Weathering Oxidation Hydrolosis Carbonation Solution
Chelating
Acid rain
Limestone ‘pavement’ that has been chemically weathered by rain. Coming up: clints and grykes! Watch for it.

4. Oxidization Metals exposed to air
Oxygen dissolved in water combines with iron molecules to form iron oxide – or rust
Red for iron, blue green for copper,

5. Hydrolysis
Carbonic acid acts on rocks containing silicon, replacing the silicon with ions of water
The rock falls apart, what is left is clay
This is the chemical process that creates the deep soils of the Amazon other rain forests
feldspar creates clays and is the most common weathering reaction on earth – that is why so much sedimentary rock is clay

6. Chelating – really biochemical weathering
When decomposing organic matter in the soil releases organic acids
These acids attack certain minerals in the rock and then release iron and aluminum ions which can be transported away by water

7. Carbonation Rainwater falls through the atmosphere
Picks up/dissolves small amounts of CO2 gas
The water is now a weak solution of carbonic acid
The calcium in limestone is dissolved by the water and the rock erodes
Other minerals in rocks are washed away this way as well. This is called SOLUTION
The most soluble elements in rocks are:
Calcium, magnesium, sodium and potassium

8. Limestone – dissolved by solution
Limestone is an organic sedimentary rock, made up of calcium carbonate that comes from the tiny shells and micro skeletons that fell to the sea bed
Layers compressed under softer conditions create chalk, while medium pressure creates limestone and extreme pressure forms it into a metamorphic rock called marble

9. Vimy Ridge Memorial, France
Designed by Canadian sculptor and architect Walter Seymour Allward, the monument took eleven years to build. It rests on a bed of 11,000 tonnes of concrete, reinforced with hundreds of tonnes of steel. The towering pylons and sculptured figures contain almost 6,000 tonnes of limestone brought to the site from an abandoned Roman quarry on the Adriatic Sea (in present day Croatia).
Vimy Ridge Memorial, France

10. A cloaked figure stands at the front, or east side, of the monument overlooking the Douai Plain. It was carved from a single, 30-tonne block and is the largest piece in the monument. This sorrowing figure of a woman represents Canada—a young nation mourning her dead. Below is a tomb, draped in laurel branches and bearing a helmet and sword.

11. Silt and Clay
Mechanical weathering creates SILT, called LOESS if deposited by wind
Chemical weathering creates CLAY (hydrolosis)

12. Acid Rain
Precipitation is already a little acid (think solution and the dissolving of limestone)
Can be caused by supervolcanic eruptions or meteors and can cause severe environmental damage in these catastrophic situations
Today, human activities create acid deposition – S02 and nitrogen oxide
Smelting, burning fossil fuels, nitrogen oxygen from automobiles

13. Effects of Acid Rain
Limestone buildings can be damaged (weathered) by acid rain, but the impact on the natural environment is huge
Limestone helps to neutralize the acid rain somewhat, but granite does not