Transcript Weathering and Soil - Grosse Pointe Public School System

 Weathering:
• breaking down of rocks, soil and minerals as
well as artificial materials through contact with
the Earth's atmosphere, organisms and water.
• Two basic types
 Physical/mechanical
 Chemical
 Frost/Ice
wedging
• Water seeps into open spaces and freezes.
• Expansion of water wedges and cracks material
• Breaks at distinct angles
 Exfoliation
• also known as unloading, overlying materials
(not necessarily rocks) are removed (by erosion,
or other processes)
• which causes underlying rocks to expand and
fracture parallel to the surface
 Plant
roots
• seedlings sprouting in a crevice and plant roots
exert physical pressure
• Provide a pathway for water and chemical
infiltration.
Paper beats rock 
 Abrasion
• mechanical scraping of a rock surface by
friction between rocks and moving particles
during their transport by wind, glacier, waves,
gravity, running water or erosion.
• moving particles dislodge loose and weak
debris from the side of the rock.
 Oxidation:
• Materials react with Oxygen from atmosphere or
water (H2O)
• Most common Iron (Fe) “rusting”
 Hydrolysis(water):
• Materials react with water to form new material
• Water dissolves rock
• Chemicals in water react
 Dissolution:
• Acid dissolved in water dissolves rock
Reactions
• carbon dioxide + water → carbonic acid
• CO2 + H2O → H2CO3
• carbonic acid + calcium carbonate → calcium bicarbonate
• H2CO3 + CaCO3 → Ca(HCO3)2
 Plant
Acids:
• Some plants produce weak acids that
seep into rocks and dissolve certain
minerals
• Examples : Lichens and Mosses
ROCK COMPOSITION

Rocks are made of minerals
CLIMATE

• Slow weathering
• Polar regions
• Tougher the mineral the
slower the weathering


Dry and Hot
• Slow weathering
• Desert regions
Surface area
• More area exposed to
weathering forces, faster
the weathering
Very cold( no change)

Moderate (warm
summer/cold winter)
• Fast weathering
• Temperate regions
Clicker
• While doing a standard pH test on
uncontaminated rain water, you
observe a pH of 5, this result indicates
that:
a) Rain water is slightly more
basic/alkaline
b) Rain water is neutral
c) You made an error
d) Rain water is acidic
Times
Timer
up!
SMART Response Question
T o set the properties right click and select
SMAR T Response Question Object->Properties...
 pH
concentration
• “power of Hydrogen”
Lower pH = more H+ ion (acidic)
 Higher pH= less H+ more OH- ion
(basic or alkaline)

1
x 10 – pH =Concentration
1
x 10 -2.5= .003
 1 x 10 -6.5= .0000003
• .003/.0000003= 10000 times more concentrated
 Or
6.5-2.5=4
• 104 =10000
 Bedrock:
• Solid un-weathered rock below the surface
 Regolith:
• layer of loose, weathered material covering solid
rock.(bedrock)
 Minerals
• 54% weathered rock
• Rocks are made of minerals
 Water
• 25% water
 Gases
• 25% Air
 Humus (organic matter):
• 5% organic material
 Explain
the relationship between
weathering and soil formation.
• Weathering and erosion make soil
 Soil
profile: Cross section, shows layers
top to bottom
O. Organic materials
A.
Topsoil (organic material)
B.
Subsoil minerals collect
C.
Regolith
R. bedrock
SMART Response Question
T o set the properties right click and select
SMAR T Response Question Object->Properties...
Clicker
• Soil is formed as a result of which
of the following:
Times
Timer
up!
a)Weathering of rocks and minerals
b)Decaying of plants and animals
c)Microorganisms adding Nitrogen
d)All of the above
 Tropical
climate:
• Rain and High temperatures cause thick infertile
soils to develop.
 Desert:
• Low precipitation causes thin soil
 Arctic:
• Slow weathering creates thin soil