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Weathering: Mechanical or Chemical?. (Take notes as we go through the slide show.). What is Mechanical Weathering?. The process that breaks rocks into different shapes and smaller pieces. (Changes the rock’s physical appearance).

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weathering mechanical or chemical

Weathering:Mechanical or Chemical?

(Take notes as we go through the slide show.)

what is mechanical weathering
What is Mechanical Weathering?

The process that breaks rocks into different shapes and smaller pieces.

(Changes the rock’s physical appearance)

slide3

TEMPERATUREHeating & cooling cause rocks to expand and contract. Temperature changes cause outer layers of rock to crack .Exfoliating is when the outer layers of rock crack and break off .

slide6
FROST ACTIONLiquid water seeps into cracks and expands when frozen causing small cracks to widen and open up
slide10
ORGANIC ACTIVITYAnimals scratch and dig on the surface breaking rocksPlant roots break up soil, even asphalt and concrete
gravity
GRAVITY
  • Gravity can pull loosened rocks down hills or mountains in a landslide, when mixed with water, it is a mudslide
gravity landslide
Gravity:Landslide

Mechanical (Physical)

abrasion
ABRASION
  • Wind carrying particles smooth rocks on the surface
  • Water carrying particles smooth rocks in rivers/oceans
abrasion wind sand
Abrasion: Wind & Sand

Mechanical (Physical)

what is chemical weathering
What is Chemical Weathering?

The process that changes the mineral composition or chemical makeup of the rocks.

Minerals can be added or removed from rocks.

OR

Minerals in the rocks can be broken down.

water
WATER
  • Water can dissolve most types of minerals that hold rocks together – these rocks are said to be soluble which means able to dissolve
oxidation
OXIDATION
  • Oxygen chemically combines with other elements such as Iron making iron oxide or rust (orange/brownish new material)
carbonation
CARBONATION
  • When carbon dioxide dissolves into water it is called carbonic acid – think about a carbonated beverage like soda – this can dissolve rocks but is too weak to harm people or plants. It can dissolve limestone or soft rocks
sulfuric acid
SULFURIC ACID
  • Sulfur dioxide is a byproduct of burning fossil fuels and it combines with water too to form acid rain
  • Acid rain affects marble statues, paint, and metal
acid rain
Acid Rain

Chemical

acid rain1
Acid Rain

Chemical

plant acids
PLANT ACIDS
  • Plants produce weak acids that break down rocks – lichens or mosses break down rocks and can form soil
  • Also, some plants such as cactus produce acids to prevent other plants from growing too close to them
what factors affect the rate of weathering
What Factors Affect the Rate of Weathering?
  • COMPOSITION of the rock – what the rock is made up of

2. CLIMATE where rock is found

3. Amount of TIME rock is exposed to the Earth’s surface

4. Amount of EXPOSED SURFACE AREA – smaller pieces allow for more rock surfaces to be exposed

mechanical vs chemical
Mechanical vs. Chemical

Mechanical: GO FAT

Chemical: COWS P

Carbonation

Oxidation

Water

Sulfuric Acid

Plant Acids

  • Gravity
  • Organic Activity
  • Frost Action
  • Abrasion (wind)
  • Temperature
rocks
ROCKS
  • Hard solids made from one or more minerals.
  • IGNEOUS
  • SEDIMENTARY
  • METAMORPHIC
minerals
MINERALS
  • Natural, non-living solid with a chemical composition (elements from the periodic table) and a crystal structure
  • Have Differences in :
  • Color Crystal Shape
  • Luster (reflecting light) Fracture
  • Density Streak