2.  M INERALS MAKE UP MOST ROCKS  D IFFERENT MINERALS HAVE DIFFERENT PROPERTIES.  R OCKS ARE BROKEN DOWN TO FORM SEDIMENTS.

3.  H OW MECHANICAL WEATHERING BREAKS DOWN ROCKS.  H OW CHEMICAL WEATHERING CHANGES ROCKS  W HAT FACTORS EFFECT THE RATE AT WHICH WEATHERING OCCURS.

4.  W EATHERING IS THE PROCESS BY WHICH NATURAL FORCES BREAK DOWN ROCKS INTO SMALLER AND SMALLER FRAGMENTS.  C ONDITIONS IN THE ENVIRONMENT CAUSE WEATHERING  R OCKS BREAK DOWN INTO SMALLER PIECES AND SEDIMENTS.  T HESE SEDIMENTS CAN FORM ROCK OR SOIL T WO T YPES OF W EATHERING  M ECHANICAL  C HEMICAL

5.  Breaks rock apart without changing their chemical composition.  This is a mechanical process  Rocks are broken into different shapes and smaller pieces Types of Mechanical Weathering 1. Ice Wedging / Frost Action 2. Pressure Release & Exfoliation 3. Plant Root Growth /*Organic Activity 4. Abrasion 5. *Gravity 6. *Temperature

6.  The repeated freezing and melting of water in the crevices and cracks of rock.  Water turns to ice at freezing temperatures and expands. When water in the pores or cracks of rock freezes, this causes the rock to crack and break over time.  *This is what breaks up the pavement in roads and the cement in sidewalks. This action causes winter potholes.  *This action is one factor that wears down sharp mountain peaks into rounded hills.

7.  Rock under the earth is under great pressure.  This pressure pushes up against the rock, and the pressure pushes the rock itself up.  Therefore, the pressure inside the rock is high (near the bottom of the rock), the pressure at the surface is low (near the surface of the rock).  Therefore the pressure from below is released at the top of the rock.  This causes the rock to crack.  Exfoliation: The breaking of rock into sheets or layers (like an onion skin).

8.  Plants and animals can cause mechanical weathering.  Plants: Trees, bushes and other plant roots grow into cracks of rocks where they find water and nutrients (plant food). The roots grow and wedge rocks apart. This is called *root-pry. Plant roots can even break apart very large rocks.  Organic Activity  Animals: animals dig into rocky areas to find shelter or food. This digging slowly scrapes away at the rock causing it to weather.

9. Abrasion  Water can wear down rocks on riverbeds, along shorelines, and during tides.  This process of wearing down by the rubbing of one object against another (friction) is called abrasion. Gravity  Gravity pulls loosened rock down a mountain cliff.  Landslide: A large movement of rocks and soil. Temperature  Rocks can be broken by changes in temperature.  As the outside of a rock heats up it expands while the cool inside of the rock remains the same. At night the rock cools and contracts. This expanding and contracting causes particles on the surface to crack and flake off.  Exfoliation: Breaking of the rock in curved sheets or slabs.

10.  W ATER A IR AND OTHER SUBSTANCES REACT WITH THE MINERALS IN ROCK.  T HIS CAUSES THE CHEMICAL COMPOSITION OF THE ROCK TO CHANGE. S OME ROCKS DISSOLVE, OTHERS ARE CHANGED INTO DIFFERENT MINERALS. Types of Chemical Weathering 1. Dissolving 2. Rusting

11. 1. Water 2. Carbonic Acid 3. Plant Acid 4. Sulfuric Acid Water  Some minerals dissolve in ordinary water. Examples: salt and halite *Carbonic Acid Carbon dioxide (pollution from cars, fossil fuels, and decaying organic matter) dissolves in water forming a weak acid called carbonic acid.  When Carbonic acid reacts chemically with another substance it is called *carbonation. water + carbon dioxide = carbonic acid

12. A. *Acid Rain This acid is formed when carbon dioxide in the air dissolves in rain. B. Pollutants increase the amount of carbon dioxide in the air. C. Carbonic acid reacts with calcite the main mineral in limestone. D. Granite : Carbonic acid reacts with the granite mineral feldspa r to form the mineral in clay called Kalolinite.

13. *Plant Acids  Some plants give off weak acids that breakdown rock. Examples: Lichen and moss *Sulfuric Acid  This acid is very strong. It is formed when pollutants from coal burning and other combustion emit sulfur oxides into the air. These compounds mix with rainwater. *Rusting Many common minerals contain iron. When these iron minerals dissolve in water, oxygen in the air combines with the iron to form iron oxides or rust. *Oxidation  Oxygen chemically combines with another substance. Example: Iron in rocks combine with air to form rust.

14. Weathering occurs at different rates depending on the following factors. *Surface Area: The more of a rocks surface that is exposed to the air, the faster it will break down. *Rock Composition: A. Different rocks break down at different rates. B. Rocks that resist weathering are called * Stable Rock *Climate: A. The amount of water and heat influence weathering. The climate effects weathering of rock. B. Example: Granite is stable in cool dry climates, but weathers quickly in tropical climates C. Heat causes weathering to happen more quickly. *Pollution: The amount of pollutants effect weathering. *Vegetation: The amount and kinds of vegetation effect weathering. *Time: The length of time a rock is exposed to the Earth’s surface affects the amount of weathering.