aim: what is weathering? do now – choose one of the following pictures and describe what is/has...
TRANSCRIPT
AIM: What is Weathering?
Do Now – Choose one of the following pictures and describe what is/has
happened.
I. Weathering the breaking down of a rock into
small pieces.
As Surface area increases the amount ofWeathering increases
II. Mechanical (Physical) Weathering
- changing the size and shape of the rock.
Abrasion:
rocks hitting and smashing against each other.
III. Types of Mechanical Weatheringa) Frost Wedging
Do Not Copy
the expansion of frozen water in cracks of rockscause it to break.-This broken material is called talus
What happens to water when it freezes?
b) Biological Activity -
organisms, plants, burrowing animals, and humans break down rocks.
IV. Chemical Weathering
changing the rocks chemical composition.
- forms a new material.
* Water is the most important agent.*
Acid Rain Damage
Soluble:
a material that can be dissolved by water.
V. Types of chemical weathering
a) Acid Rain
- water combines with different elements to make acids.
- this is known as Hydrolysis.
- H2O + carbon dioxide = carbonic acid
* - H2O + sulfur = sulfuric acid (acid rain)What material will all these acids react
with?
Do Not Copy
•Acid rain reacts with calcite and dolomite in the rocks (Limestone).
•This dissolves the rock creating Karst Topography (caves), stalactites and stalagmites.
b) Oxidation
- Water and oxygen react with metal to create rust.
VI. Rate of Weathering
A) Rock Characteristics:
- Mineral composition and solubility of the rock (the minerals that make the rock) determine the rate of weathering.
Granite Limestone
- amount of surface area determines amount of weathering
- Some rocks are more resistant (harder) to weathering. Mineral composition is the greatest determining factor.
Hoodoo
In the diagram below, which letter rock is most resistant
to weathering?
B) Climate:
- Temperature and moisture are the most crucial factors.
- Chemical weathering is most effective in areas with high temperatures (heat)
and abundant moisture (water).
Explain the difference in weathering of the two headstones (roughly the same age). What
caused the difference in weathering?
Slate Headstone Marble Headstone
Closure: In your Notes
Cleopatra’s Needle
1900 - EgyptPresent Day -Central Park
2) Describe one factor that
explains why Cleopatra’s
needle changed after it was
brought from Egypt to New
York.