weathering and soil

1. 1
Weathering, Soil, and
Mass Movement

2. 2
WWhhaatt iiss WWeeaatthheerriinngg??
The breaking
down and changing
of rocks near
Earth’s surface

3. MMeecchhaanniiccaall ((PPhhyyssiiccaall))
WWeeaatthheerriinngg??
 Physical forces
break rock into
smaller pieces
without changing the
rock’s composition.
3

4. MMeecchhaanniiccaall WWeeaatthheerriinngg--
In nature there are 3 main causes to mechanical
weathering:
Frost wedging, unloading, and biological activity
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5. FFrroosstt WWeeddggiinngg
Expansion of freezing
water in cracks and
crevices
Eventually breaking
rocks into pieces
• Sections of rock that are
wedged loose may
tumble into large piles
called talus
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6. UUnnllooaaddiinngg
• Large masses of
igneous rock may
be exposed
through uplift and
erosion of
overlying rocks
• Resulting in
reduced pressure
Exfoliation—slabs
of outer rock
separate and
break loose
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7. 7
BBiioollooggiiccaall AAccttiivviittyy
• The activity of plants- roots
breaking rock
• burrowing animals-moving
rocks to places where
weathering more rapidly occurs,
and humans
• Decaying organisms- producing
acids
• Humans- because of
deforestation, creation of roads,
and blasting mineral

8. CChheemmiiccaall
WWeeaatthheerriinngg??
 the
transformation of
rock into one or
more new
compounds
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9. Agents and EEvviiddeennccee ooff CChheemmiiccaall
Oxygen, water , and carbon dioxide are in
chemical weather
Water: most important agent of weathering. It
picks up CO2 and SO2 in the air which forms
acid rain.
Or dissolves these compounds into cracks of
rocks
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WWeeaatthheerriinngg

10. RRaattee ooff WWeeaatthheerriinngg
How fast the rocks
erode
Two factors
• Rock characteristics
• Mineral composition
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and solubility
• Climate
• Temperature and
moisture
• Favors high
temperature and
abundant moisture

11. 11
SSooiill
part of the
regolith that supports
the growth of plants.

Regolith: layer of rock
and mineral fragments
that covers Earth’s land
surface.

12. HHooww iiss SSooiill FFoorrmmeedd??
By rock being
eroded away.
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13. CChhaarraacctteerriissttiiccss ooff
13
SSooiill
Soil Composition
Soil has four major
components
◦ A. Mineral matter
(broken-down rock)
◦ B. Humus (decayed
remains of
organisms)
◦ C. Water
◦ D. Air

14. CChhaarraacctteerriissttiiccss ooff
SSooiill
 Texture refers to
the proportions of
different particle
sizes.
 A. Sand (large
size)
 B. Silt – feels
like flour
 C. Clay (small
size)
 D. Loam (a
mixture of all three
sizes) is best suited
for plant life.

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

15. CChhaarraacctteerriissttiiccss ooff SSooiill
15

16. TTiimmee,, CClliimmaattee,,
OOrrggaanniissmmss aanndd SSllooppee
Time:
 The longer a soil has been forming, the thicker
it becomes.
Climate
 Greatest effect on soil formation
Organisms
 Furnish organic matter to soil
Slope
 Steep slopes often have poorly developed soils.
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17. Soil Types Location Contents
Pedalfer under forest
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vegetation
iron oxides and
aluminum-rich
clays in the B
horizon
Pedocal drier grasslands Calcium carbonate
Laterite Hot, wet, tropical
climates
Intense chemical
weathering to the
top layers of soil

18. HHooww ddooeess
wwaatteerr eerrooddee tthhee
ssooiill??
Rain uses gravity as
a force to move soil.
Flash flooding and
runoff of water
causes erosion
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19. 19
PPrroocceesssseess ooff WWaatteerr
EErroossiioonn
1. Sheet erosion -
2. Rills (tiny streams)
3. Gullies (trenches)
4. Transports sediments for
deposits.

20. WWhhaatt iiss MMaassss
MMoovveemmeenntt??
The transfer of
rock and soil
down-slope due
to gravity
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21. TTrriiggggeerrss ooff MMaassss MMoovveemmeenntt
Water Heavy rains and rapid melting
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of snow
Oversteepened Slopes The steeper the slope the
greater the chance for
movement
Removal of
vegetation
Roots keep the soil intact.
Removing plants causes
erosion
Earthquakes Aftershocks dislodges rocks

22. CCllaassssiiffiiccaattiioonn ooff
MMaassss MMoovveemmeennttss
Rockfalls occurs
when rocks or rocks
fragments fall freely
through the air.
Avalanches
extremely rapid
movement of earth
material or snow
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23. Slides
A block of material moves
suddenly along a flat,
inclined surface.Slides
that include segments of
bedrock are called
rockslides.
Slumps
 The downward
movement of a block of
material along a curved
surface.
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24. Flows
 contain a large
amount of water.
 Mudflows move
quickly and carry a
mixture of soil,
rock, and water
 Earthflows move
relatively slowly
and carry
clay-rich sediment.
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25. 25
 Creep is the
slow, downhill
movement of
soil and
regolith.
