LO: What is Weathering? Do Now: Write Lab #19.

Look at the pictures below, discuss with your partner what is/has happened in each. f h g

- breaking down of a rock into sediment ** Reminder** What is weathering? - breaking down of a rock into sediment

Mechanical Weathering There are 2 forms of weathering: Mechanical Weathering (Physical) changing size and shape - Breaking a rock into smaller pieces without changing it’s chemical composition. - Happens best in a dry (arid) climate.

Chemical Weathering - Breaking a rock into smaller pieces by changing it’s chemical composition. (It forms a new material) - Happens best in a hot wet climate.

Types of Mechanical Weathering Frost wedging Rocks break apart when liquid water seeps into cracks then freezes and expands Common example are Potholes

Root Action Roots of plants grow and move underground causing enough pressure that the rock breaks

Unloading When an igneous intrusion is uplifted to the surface allowing room for it to expand. Large portions of the top layers break off.

Which pictures are examples of mechanical weathering? b c f h g

Types of Chemical Weathering Hydrolysis The chemical reaction of rain water with another substance. (nitric and sulphuric acids)

Oxidation The chemical reaction of oxygen with another substance. (iron oxide – rust)

Carbonic Acid When carbon dioxide is dissolved in groundwater it creates a weak acid that breaks down various clay minerals. (limestone) Caves

Which pictures are examples of Chemical weathering? b c f h g

Now that we know what Weathering is, What Are Some Factors That Can Affect Weathering ?

the more time exposed, the more weathering will occur.

A solid rock has the least surface area. (The interior is protected) A ground up rock has greatest surface area exposed. (The interior can now be attacked.) A solid rock has the least surface area. (The interior is protected)

The more surface area a rock has exposed, the more weathering will occur.

- some minerals are more resistant than others. Mineral composition- - A minerals hardness determines it’s resistance to weathering - some minerals are more resistant than others.

ESRT pg 16 Garnet or Quartz Talc Where could you look to find a minerals hardness? ESRT pg 16 Which mineral would be most resistant to weathering? Garnet or Quartz Which mineral would be least resistant to weathering? Talc

Climatic Conditions: Cold and/or dry climates favor physical weathering. High Elevations - Frost action works best because the temperature fluctuates above and below freezing. Warm and wet climates favor chemical weathering. Chemical reactions occurs faster in warmer environments

F because it is the tallest which means it hasn’t weathered as much. Looking at this area, which rock layers is most resistant to weathering? Explain A B C D E F because it is the tallest which means it hasn’t weathered as much.

3 - Most resistant to weathering This also works on a cliff. Looking at this area, which rock layer is most resistant to weathering? Least resistant to weathering? 3 - Most resistant to weathering 2 - Least resistant to weathering

Looking at this area, which rock layers is most resistant to weathering? A, C, and E have the steepest (sharpest) edges

Why did these ridges form? The ridges are more resistant to weather and the valleys are least resistance to weathering.