7.1 Flashcards
Weathering?
The process by which rocks on or near Earth’s surface break down or change.
Erosion?
Removal and transport of weathered material from one are to another.
Mechanical weathering?
The process by which rocks and minerals break down into smaller pieces. Does not involve any change in rocks composition, only the size and shape.
Frost Wedging?
The repeated thawing and freezing of water in the cracks of rocks that is responsible for potholes.
Exfoliation?
The process by which outer layers of rock are stripped away.
Chemical weathering?
The process by which rocks and minerals undergo changes in their composition. SIgnificant agents include water, oxygen, carbon dioxide, and acid. Chemical reactions result in the formation of new minerals and the release of dissolved substances.
Hydrolysis?
The reaction of water with other substances. Occurs in the decomposition of silicate minerals.
Oxidizer ion?
The chemical reaction of oxygen with other substances. Ex. Rust.
Why did Cleopatra’s needle become worn after 75 years in New York?
Due to the weathering that took place there as a result of the different climate conditions. More moisture.
What was Cleopatra’s needle made out of?
Granite
What are the two factors that play a role in mechanical weathering? Briefly explain how.
Temperature: when water freezes it expands and increases in volume. When water collects in the cracks of rock and rock layers on Earth’s surface, the water expands and causes the rock to split. When the temperature increases, the ice layer melts. This repeated process of thawing and freezing is called frost wedging (responsible for potholes).
Pressure: when overlying layers of rock on bedrock are removed, the pressure decreases. The bedrock then surgaces and expands, causing cracks to form. Over time, outer layers of rock are stripped away in a process called exfoliation.
What do chemical reactions between rocks and water produce?
New minerals and the release of dissolved substances.
What does the composition of rocks determine?
The effects that chemical weathering has on them because when chemical reactions occur, and new minerals form, the new minerals have different properties from those of the original rocks. Some minerals, such as calcite, may dissolve completely. Rocks that contain calcite are greatly affected by chemical weathering.
How does temperature affect chemical weathering?
It influences tha rate at which chemical reactions occur. Usually chemical reaction rates increase as temperature increases.
What are the four significant agents of chemical weathering and what are their roles?
Water- dissolves many kinds of minerals and rocks. Has an active role in some reactions and can serve as a medium for which other reactions occur.
Oxygen- can combine with other substances in an process known as oxidizer ion.
Carbon Dioxide- when carbon dioxide combines with water in the atmosphere, it forms carbonic acid that falls to the Earth as precipitation and reactions with minerals to dissolve rock. Carbonic acid also results in the formation of clay minerals when high concentrations occur in soil. When water seeps in the ground and combines with CO2 large amounts of carbonic acid become available for chemical weathering.
Acid precipitation- caused mainly by the oxidization of suffer dioxide and nitrogen oxides. The two gases combine with oxygen and water in the atmosphere to form Sulfuric and nitric acid. Acid precipitation has a pH of below 5.6. Acid precipitation is destructive to non-living things and harmful to organisms.
How does climate affect the rate of weathering using examples?
Climate affects the rate of weathering because chemical weathering occurs readily in areas with warm temperatures, abundant rainfall, and lush vegetation. Physical weathering occurs readily in cool, dry climates and rates are highest in areas where water undergoes repeated thawing and freezing.
Ex. How is is dry and warm and temp does not drop below freezing. Asheville temp can drop below freezing and they have more rainfall and humidity. Therefore, rocks and minerals in Ashville receive higher rates of mechanical and physical weathering.
How does rock type affect the rate of weathering?
How hard or resistant they are depends on their type and composition. Sedimentary rocks are more easily weathered than harder igneous and metamorphic rocks such as the dramatic landscape in the Bisti Badlands.
How does surface area affect the rate of weathering?
Mechanical weathering breaks rocks into smaller pieces which increases their surface are so more surface area is available for chemical weathering.
How does topograph affect the rate of weathering?
Materials on level areas are liekly to remain in place as they undergo changes whereas materials on slopes have a tendency to move, and as it move sit exposes underlying rock which provides more opportunities for weathering to occur.
How do other variables affect the rate of weathering?
Organisms as decaying organic matter and plant roots release carbon dioxide which combines with water to produce acid, which increases the weathering rate.
Weathering vs. Erosion?
Weathering is the process by which rocks on or near Earth’s surface break down or change and erosion is the movement or transport of weathered material from one area to another.
What are the variables that affect the rate of weathering?
Climate (precipitation, temperature, evaporation) as chemical weathering occurs in warm areas with rainfall and physical weathering occurs in cool, dry climates; rock type an composition (how hard or resistant they are); surface area (greater surface area = more weathering); topography (level areas less likely to move than sloped areas); organisms (decaying organic matter and living plants release CO2 which combines with water to produce acid).
What are the two most important climatic factors in weathering?
The interaction between temperature and precipitation. Climates with warm temperatures and abundant rainfall accelerate chemical weathering hole cool and dry climates accelerate physical weathering.
What is an example of Ho wome variable may affect another with weathering?
An area with warm temperatures and abundant rainfall will lead to a vegetation increase and plants release CO2 which combines with water to produce acid which increases the weathering rate.
