Weathering ang Erosion

Question 1

is the decomposition
and disintegration of rocks and
minerals at the Earth’s surface.

It involves little or no
movement of rocks and minerals – the weathered material accumulates
where it forms and overlies
unweathered bedrock.

Answer 1

Weathering

Question 2

is the removal of weathered
rocks and minerals by moving water,
wind, glaciers, and gravity. After a
rock fragment has been eroded from
its place of origin, it may be
transported large distances by the
agents mentioned above.

Answer 2

Erosion

Question 3

When the wind or water loses energy,
or when the ice carrying the
weathered material melts, transport
stops, and sediment is _________

Answer 3

deposited

Question 4

wetlands that form as rivers
empty their water and sediment into
another body of water

Answer 4

delta

Question 5

reduces solid rock to rubble but does not alter the chemical composition of rocks and minerals.

Answer 5

Mechanical weathering

Question 6

occurs when air and water chemically react with rock to alter its composition and mineral content.

Answer 6

Chemical weathering

Question 7

Five major processes of Mechanical Weathering

Answer 7

1. Pressure-release fracturing
2. Frost wedging
3. Abrasion
4. Organic activity
5. Thermal expansion and contraction

Question 8

as pressure diminishes, rock expands – which leads to fracturing of brittle rock.

major processes of Mechanical Weathering

Answer 8

Pressure-release fracturing

Question 9

water expands when it freezes. If water accumulates in a crack then freezes, its expansion pushes the rock apart

major processes of Mechanical Weathering

Answer 9

Frost wedging

Question 10

mechanical weathering and grinding of rock surfaces by friction and impact.

major processes of Mechanical Weathering

Answer 10

Abrasion

Question 11

roots may work their way down into cracks in the
rock, expand, and eventually push the rock apart.

major processes of Mechanical Weathering

Answer 11

Organic activity

Question 12

rocks are exposed to daily and yearly cycles of heating and cooling , which, as a result, the surface expands or contracts faster than the interior

major processes of Mechanical Weathering

Answer 12

Thermal expansion and contraction

Question 13

Chemical Weathering
Three most important processes:

Answer 13

1. Dissolution
2. Hydrolysis
3. Oxidation

Question 14

rocks are made up of minerals, and minerals are
chemicals on their own. To understand how acids and bases dissolve minerals , think of an atom on the surface of a crystal, which could be dissolved when subjected to the certain solvents.

Chemical Weathering

Answer 14

Dissolution

Question 15

water reacts with a mineral to form a new mineral with the water incorporated into its crystal structure.

Chemical Weathering

Answer 15

Hydrolysis

Question 16

many minerals react with atmospheric oxygen , O2 Rusting is one example of a more general process called __________

Chemical Weathering

Answer 16

Oxidation

Question 17

Significance of Weathering

Answer 17

most important aspect of weathering is its role in the formation of soil.

Weathering is important to engineers because it can help them to understand **how buildings and other structures will be affected by the environment. **

Weathering is also important to geologists because it can help them to study the history of the earth’s surface.

Question 18

The Effects of Weathering (3)

Answer 18

• weakening of intact rock blocks and soil grains
• integral become mechanical discontinuities (i.e. bedding planes not being yet a mechanical plane
  of weakness become a mechanical
  plane of weakness)
• material between rock blocks becomes weaker (remains of weathered material)

Question 19

when a rock mass is weathered, there are: (3)

Answer 19

• Weaker rock blocks and soil grains;
• Smaller rock blocks and grains; and
• Lesser shear strength between blocks and grains.

Question 20

what gives rock and soil masses strength

Answer 20

Rocks and soil masses consist of:
* intact blocks (rock) with discontinuities in-between (e.g. bedding plances, joints, fractures, etc.)
* grains (in soil) with grain contacts in-between

Strength of a mass is given by:
* strength (shear and tensile) of intact rock blocks or soil grains
* shear strength between blocks (rock) or grains (soil)

Question 21

Weathering products from mechanical and chemical
weathering may accumulate on the Earth over bedrock . This material is called _____________.

Answer 21

regolith

Question 22

are the upper layers of
regolith that support plant growth.

Answer 22

soil

Question 23

soil profile

Answer 23

O horizon
A horizon
B horizon
C horizon

Question 24

Typical mature soil consists of
several layers called ________

Answer 24

soil horizons.

Question 25

**Combination of O and A** horizons are called __________ .

Answer 25

topsoil

Question 26

named for its **Organic** component.

Answer 26

O horizon

Question 27

mixture of **humus, sand, silt, and clay**. Also called **zone of leaching** .

Answer 27

A horizon

Question 28

also called **subsoil or zone of accumulation**, is a transitional zone **between topsoil and parent rock** below.

Answer 28

B horizon

Question 29

consists of **partially weathered rock that grades into unweathered parent rock.**

Answer 29

C horizon

Question 30

degrees of weathering

Answer 30

1. fresh 2. slightly weathered 3. moderately weathered 4. highly weathered 5. completely weathered 6. residual soil

Question 31

**No visible sign of rock material weathering** ; perhaps **slight discoloration** on major discontinuity surface | degrees of weathering

Answer 31

1. fresh

Question 32

**Discoloration** indicates weathering of rock material and discontinuity surfaces. **All rock material may be discolored by weathering** | degrees of weathering

Answer 32

2.slightly weathered

Question 33

**Less than half** of the rock material is **decomposed or disintigrated to a soil** . Fresh or discolored rock is present either as a **continuous** framework or as core stones | degrees of weathering

Answer 33

3.Moderately weathered

Question 34

**More than half** of the rock material is **decomposed or disintigrated to a soil.** Fresh or discolored rock is present either as a **discontinuous** framework or as core stone. | degrees of weathering

Answer 34

4.Highly weathered

Question 35

**All rock material is decomposed** and/or disintigrated to soil. The **original mass structure is still largely intact.** | degrees of weathering

Answer 35

5.Completely weathered

Question 36

**All rock material is converted to soil.** The mass structure and material fabric is destroyed. There is a **large change in volume,** but the **soil has not been significantly transported.** | degrees of weathering

Answer 36

6.Residual soil