Chapter 5: Weathering and Erosion

What are the three important functions of water?

-Carries ions to reaction site -Participates in reaction -Carries ions away from reaction site

What are three kinds of weathering?

-Mechanical fragmentation -Chemical alteration -Solution

-What is mechanical weathering? -What is chemical weathering?

-Mechanical weathering is physically breaking a rock into smaller pieces. -Chemical weathering is altering the composition of rocks and minerals.

-What is regolith? -What is soil?

-Regolith or "rock blanket" is a fragmented material covering the bedrock. -Soil is the upper few meters of regolith that supports life.

What are the three primary factors that influence mass wasting?

1) The nature of the slope materials (consolidated vs. unconsolidated) 2) The amount of water in the material 3) The steepness of the slope

What is frost wedging?

1) Water enters cracks in a rock. 2) Water freezes as the temperature decreases; expands against walls of rock. 3) Cracks are enlarged; the rock breaks.

What is the relationship between changes in levels of atmospheric weathering and the rate of weathering?

Lower temperature and decreases in atmospheric CO2 reduce weathering. Reduced weathering leads to increase in CO2, which leads to climate warming, which in turn, increases weathering. Weathering reduces CO2 in the atmosphere. Lowered CO2 leads to climate cooling and the cycle starts all over.

What is mass wasting?

Mass wasting or mass moving, commonly referred to as landslides is when gravity drags down large amounts of sloper forming material all at once.

How does mechanical weathering effect surface area?

Mechanical weathering increases the surfaces area for chemical weathering.

Hills made from consolidated material form what kind of slopes?

Hills made of consolidated material can generally form steeper slopes.

How can roots of plants cause mechanical weathering?

Plant roots can cause mechanical weathering by growing through and around rocks. They expand through the rock causing it to crack.

How can the growth of salt crystals cause mechanical weathering?

Rocks that are exposed to sea water get salt n their cracks. The salt expands cracking the rock.

What is the relationship between formation of a rock to the ease of weathering a rock?

The longer a rock takes to form the more stable it becomes. Meaning it is harder to weather it.

What happens to a rock as it tumbles down a stream?

The rock becomes smaller.

What is thermal expansion and contraction?

A rock is formed in the Earth where it is hot, when it comes to the surface it cools. These cooling causes shrinking, which causes the rock to crack.

What is abrasion and where can it occur in nature?

Abrasion is breaking rocks into smaller, smoother, and roundish shapes. In nature this happens on beaches and in rivers.

How can animals cause mechanical weathering?

Burrowing animals, burrow in between the rocks, causing them to crack.

What does chemical weathering involve?

Chemical reactions involve water.

What else can thermal expansion and contraction cause? What rock is it common in?

Exfoliation. Which is the cracking and breakage of just the top surface of a rock. This is common in igneous rocks.

What factors influence chemical weathering?

Climate. Increased wetness and increased in warm climate increase the rate of chemical weathering.

What is cohesion?

Cohesion is an attractive force between particles, stronger cohesion force means more resistance to movement.

What is oxidation?

Oxygen reacting with a element to create a new mineral.

What factors influence soil formation?

Parental material, climate, topography, vegetation, and time.

How to do hills made of unconsolidated materials-such as sand and silt-behave?

Particles dropped in a pile create an angle of repose based on their size and angularity. Fine sand assumes a shallower angle of repose than angular pebbles do.

What is hydrolysis?

Water reacts with an element breaking it into minerals + ions

How does surface area change as rocks get smaller? How does volume change as rocks get smaller?

Surface area becomes larger (doubles) as rocks get smaller. The volume stays the same.

How does water content and steepness effect slope stability?

Water can lubricate the planes of weakness in the ground, allowing material to slide more easily, even to the point where it flows like like liquid, liquefaction.

How does water effect mass wasting?

Water is an important factor, and can increase cohesiveness (surface tension), or drastically decrease cohesiveness (water saturation).

What is dissolution?

Water reacts with an element and combines with it making a new mineral.

What does the process of weathering silicates, such as feldspar do to the atmosphere?

Weathering of silicates such as feldspar removes carbon dioxide from the atmosphere.