Geology - Chapter 6

What is salt weathering?

the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart

Pre-existing rocks are broken down into smaller particles by which of the following processes?

-unloading -thermal expansion -frost wedging

Which of the following components make up a healthy soil?

-water and air -mineral matter -organic matter -organic matter and mineral matter all of the above

Match key terms to appropriate sentence. Be sure to complete each sentence before submitting your answer. 1. _______ has a crucial influence on the rates of all types of mechanical weathering 2. ___________________ can contribute to crumbling roadways in areas where salt is spread to melt ice and snow in winter 3. The fissures formed as a result of ________ in exfoliation domes can be further enlarged by _____________ in areas subjected to seasonal freeze-thaw cycles 4. The break down of rock by moving fresh materials to the surface by burrowing animals is an example of mechanical weathering due to ___________________

1. Climate 2. Salt crystal growth 3. Sheeting, frost wedging 4. Biological activity

What do freeze-thaw and salt weathering have in common?

Both freeze-thaw and salt weathering require rain and force rocks apart physically.

Where does the clay that accumulates in the B horizon come from?

A and E horizons

Which of the following scenarios best describes how sheeting will develop in an igneous rock?

A subterranean pluton is exposed at the surface, releasing confining pressure.

Which of the three images in Figure 2 would be most susceptible to chemical weathering and why?

C: Physical weathering has created more surface area for chemical weathering to attack.

Considering the following list, which is not an example of chemical weathering?

exfoliation

The processes of chemical weathering results in the decomposition of minerals within rocks over time. Fill in the sentences below to explore the different chemical weathering processes

CHEMICAl weathering alters the internal structure of rock materials Potassium feldspar weathers in the presence of water containing CARBONIC ACID Iron weathers through the process of OXIDATION A greenhouse gas called CARBON DIOXIDE influences the rate of chemical weathering.

Using the choice you made for Part C, explain why that part of the rock would chemically weather the most quickly during spheroidal weathering.

Corners have the most surface area and provide three directions from which chemical weathering can attack.

Using what you know about spheroidal weathering, put the images in Figure 1 in order from the start of spheroidal weathering to the finish.

D, A, C, B

__________ is when various geologic materials exposed to the same environmental conditions will weather differently depending on their composition.

Differential weathering

Which part of the rock in Figure 2 will get chemically weathered the most quickly?

E (corner)

Which of the following statements regarding weathering and erosion is NOT true?

Erosion and weathering have the same definition and can be used interchangeably.

With the addition of water, the minerals in granite rocks chemically weather into other minerals, known as products. Test your knowledge of the by-product of each mineral as a result of chemical weathering by labeling the minerals below with their respective products

Feldspar-clay Quartz- No chemical change Olivine- Limonite

Rank the rocks in order of the rate of chemical weathering they would experience, assuming they are all located in the same warm wet climate.

Granite, with very few or no cracks Granite, with abundant cracks Basalt with few to no cracks Basalt with abundant vesicles (holes)

You will visually identify these types. Note that one of the images is not an example of mechanical weathering.

Top, left to right: 1. Frost wedging 2. Salt crystal growth 3. Sheeting Bottom, left to right: 1. Biological activity 2. Not an example of mechanical weathering

Which of the following locations will weather a block of marble the most quickly?

Honolulu, Hawaii

You will sort each example into its category of chemical weathering process.

Hydrolysis -Feldspar in granite rocks weathering to clay Oxidation- red color of rocks in Arches National Park -yellow-stained rocks that use to contain pyrite before it is weathered Dissolution -the salty taste of ocean water -caves formed in limestone

What is the definition of physical weathering?

Mechanical processes break substances into smaller pieces.

Read the following descriptions of several different environments. Based on the information given, sort each environment into the correct bin for an environment that would experience predominantly mechanical weathering or predominantly chemical weathering.

Mechanical weathering would predominate. A cold wet environment at high elevation, in which freezing and thawing is common. A cold dry environment experiencing uplift, in which material is being removed by erosion from an underlying pluton/intrusive igneous rock. Mechanical weathering would predominate. A cold wet environment at high elevation, in which freezing and thawing is common. A cold dry environment experiencing uplift, in which material is being removed by erosion from an underlying pluton/intrusive igneous rock.

Which soil horizon will contain the greatest amount of organic material?

O horizon

In this exercise, you will use the mineral components of various rocks to rank them based on their weathering rates. The name of each rock is provided below with each picture. The chemical compositions are

Peridotite, Gabbro, Diorite, Granite

How will physical and/or chemical weathering contribute to create rounded shapes during spheroidal weathering?

Physical weathering will fracture a rock, which leaves more area for chemical weathering to attack.

Sand dunes are typically dominated by quartz grains and very little other mineral matter. Why does this selection occur?

Quartz is extremely resistant to all forms of chemical weathering.

Think about the soil horizons that make up the solum. Why isn't the C horizon part of the solum?

The C horizon contains unweathered parent material.

Both tombstones in Figure 1 are from the same cemetery and were erected within four years of each other. Why is the younger marble tombstone more weathered than the older granite tombstone?

The quartz and feldspars in the granite are more resistant to weathering than the calcite in the marble.

During the late Cretaceous, the Bisti Badlands were home to numerous animals including turtles, crocodiles, and even dinosaurs. What type of environment were they living in?

They were living along rivers and deltas on the edge of an inland sea.

Why does water frozen in the cracks of a rock help to break down the rock?

Water expands when frozen and physically forces the rock apart.

How does physical weathering cause chemical weathering to be more effective?

When a rock is physically broken into smaller pieces, there is more surface area on which chemical weathering can occur.

Which of the following is an example of chemical weathering?

a car fender getting rusty

The chemical weathering process known as dissolution is most effective in the breakdown of which of the following minerals?

calcite

A hoodoo with a cap rock of sandstone and shale below is an example of __________.

differential weathering

In temperate and polar regions, the accumulation of talus slopes at the base of steep, rocky cliffs is most often attributed to which of the following processes?

frost wedging

Which of the following rocks would most likely experience sheeting?

granite

Look at the descriptions below of scenarios and determine whether the scenario inhibits weathering or enhances weathering.

limits weathering Rows of trees are planted on the border of a field to slow the wind and deflect it upward. Promotes weathering Humans remove trees and other vegetation in order to develop an area of land. LIchens, which secrete acids, are present on the surface of a rock. Animals burrow into the ground loosening the soil.Consistent grazing by a herd of cattle.

Of the following processes, which is not an example of mechanical weathering?

oxidation

When sheeting develops in an igneous pluton, fractures will develop in an orientation __________ to the direction of expansion.

perpendicular

The chemical weathering process known as oxidation would be most effective in the breakdown of which of the following Earth materials?

pyroxenes

Which one of the following is NOT an example of a mechanical weathering process?

reactions that occur when rain mixes with carbon dioxide to form carbonic acid

Mechanical processes break substances into smaller pieces. Submit

rusty color and fracturing

The production of tabular slabs of rocks caused by unloading of material overlying igneous bodies is known as _____.

sheeting

What changes are occurring in the igneous pluton that would result in sheeting?

volume increase

Which of the following climates will have the highest rate of weathering?

warm, wet climates

During hydrolysis, ions and clay minerals are produced by the decomposition of which of the following Earth materials?

feldspars