soil - what is weathering?

Question 1

define weathering

Answer 1

represents a response of minerals which were in equilibrium at depths within the lithosphere to conditions at or near the earth atmosphere surface

slow or no change at depths until hits surface

Question 2

why does volcanic rock go rusty brown?

Answer 2

due to chemical oxidation
weather
biological weathering

Question 3

why is weathering important?

Answer 3

converts rocks to soils and contributes nutrients to plants

prepares material for erosion and transports - influences physical and chemical behaviour of river

Landform evolution and shaping landscapes (depends on rock type and degree of weathering)

impacts buildings and heritage

Question 4

what are the results of weathering ?

Answer 4

increase bulk
decrease density
decrease particle size
decrease mechanical strength 
production of new materials -neo-formation
discolouration

Question 5

give example of weathered landmark?

Answer 5

sphinx, Giza, Egypt

almost looks like sand

Question 6

what is a weathered limited landscape?

Answer 6

As soon as material is weathered its removed by erosion and transported away

transportation faster than production

Question 7

what is a transport limited landscape?

Answer 7

Material weathered but not transported away

production faster than erosion and transportation

Question 8

what were traditional methods of classification of weathering?

Answer 8

physical
biological
chemical

ALL WORK TOGETHER CANNOT BE SEPARTED

Question 9

How do we recently classify weathering?

Answer 9

brittle fracture - scale of rock mass/ clast/ crystal - macro large scale processes

crystal lattice breakdown - molecular and submolecular - micro small scale proceses

Question 10

Surface sheeting happens as result of unloading

Answer 10

unloading - removal of great weight off rocks

eg Yosemite national park

Question 11

how is the exfoliation of rock caused ?

Answer 11

from thermal expansion and contraction - thermal stresses

hot - expands
cold - cools

causes onion skin weathering also know as spheodial weathering

Question 12

what happens to cause haloclasty of rocks?

Answer 12

water gets inside rock and water dries out leaving salt behind

salt grows and expands putting pressure on rock and cracks it

occurs in arid environment as if its too wet water wont dry salt out so little haloclaty

Question 13

what is haloclasty also called?

Answer 13

salt weathering

Question 14

what is gelifraction also called?

Answer 14

frost wedging

Question 15

What happens during gelifraction?

Answer 15

occurs in very cold env

water fills the crack and freezes when temps hit below 0 degrees

ice less dense than water, it expands and puts pressure on break breaking it down over time

eg cairngorms scotland

Question 16

what 4 brittle fracture processes are there?

Answer 16

surface sheeting from unloading

thermoclasty - exfoliation from thermal stresses

haloclasty - salt weathering

gelifraction - frost wedging

biomechanical forces

Question 17

name 3 biomechamical weathering forces

Answer 17

rock wedging in response to tree root growth

burrowing animals

lichen growth on rocks also biochemical as lichen use chemical agents on rock

Question 18

name 4 crystal lattice breakdown processes?

Answer 18

dissolution (Precipitation)

hydration (dehydration)

Hydrolysis

oxidation (redox reduction)

Question 19

define dissolution

Answer 19

resolving or dissolving parts of elements

Question 20

define precipitation

Answer 20

deposited in solid form from a solution

seprated from liquid

Question 21

define hydration

Answer 21

substance will combine with water

Question 22

define dehydration

Answer 22

loss of water molecules from reacting molecule

affected with heating

Question 23

define hydrolysis

Answer 23

water breaks down large compounds

breaking covalent bonds

creates new substance

Question 24

define oxidation

Answer 24

loss of electrons

gain oxygen

loss of hydrogen

Question 25

define reduction

Answer 25

remove oxygen

gain hydrogen

Question 26

define carbonation

Answer 26

chemical reaction of co2 to give carbonates, bicarbonates and carbonic acid

Question 27

what do dissolution and hydrolysis require?

Answer 27

an acid

most common source is atmopsheric acid

Question 28

name 3 other important acids to chemical weathering?

Answer 28

sulphuric acid - comes from combustion of coal from factories

nitric acid - anthropically produced but has natural origins

organic acids - plants create this

Question 29

what controls weathering rates name 4?

Answer 29

slope - promotes removal of weathered material by gravity

climate - temp affects chemical reactions like gelifraction and thermoclasty. Rain - acidic

bedrock type - susceptibility to chemical erosion

vegetation/biodiversity - organic acids - more weathering

Question 30

what type of rock does oxidation weathering create?

Answer 30

rocks in rich red iron oxide

rust on man made metal - zero valent