1. Definitions: Weathering: the break-up of rock at earth’s surface
Erosion: the physical removal and transport of rock material by water, wind or ice.
Mass wasting: the movement of large amounts of rock or soil downslope due to gravity (landslide)

2. Weathering Earth’s surface is constantly changing.
It is a dynamic (changing) planet.
200 years ago most people believed that mountains, lakes and deserts were permanent (static) features of the Earth.

3. Earth’s surface is continually being sculpted by…
Name 5 forces….
Water
Wind
Ice (glaciers)
Plate Tectonics (Volcanoes/Earthquakes)
Biological (humans)

4. Weathering processes are part of the rock cycle.

5. Weathering is an External process
Processes that occur on the Earth’s surface (wind, water, ice)
get their energy from the Sun.

6. Internal processes
These processes that change the earth’s surface, get their energy from magma within the Earth (mantle)
Plate tectonics change shape, size and location of land masses.
Volcanic activity
Mountain building
Earthquakes

7. Mechanical (physical) weathering
(Def.) The physical break-up and the
chemical decomposing of rock due to exposure and processes at or near the Earth’s surface.
It’s a s-l-o-w and subtle process.
All materials are susceptible to weathering
Two types of weathering:
Mechanical (physical) weathering
Chemical weathering

8. Mechanical (physical) weathering
The disintegration, fragmenting, splitting, breaking of rock into smaller and smaller pieces.
The rock’s mineral composition remains unchanged.

9. Mechanical weathering involves several physical processes:
1. Frost wedging
2. Abrasion
3. Exfoliation
4. Biological activity

10. Frost wedging Repeated freezing and thawing.
Water expands about 9% in volume when it freezes.
Expanding exerts tremendous outward force.
Water works it way into cracks and pores in rocks, breaking them into pieces when it freezes-thaws.

12. Frost wedging

13. Weathered rock piles-up at the base of a cliff forming a TALUS slope

14. Talus (weathered rock rubble) at the base of a slope

15. Frost-wedging occurs in mid-latitudes (that’s us) and mountainous regions where daily freeze-thaw weather exists.
(not Florida)
Frost wedging is responsible for pot holes and road repairs.

16. Abrasion: Due to … Water Wind Glaciers
The scraping and wearing down of rocks.
Due to …
Water
Wind
Glaciers

17. Abrasion by water: Rocks tumble and collide as they are carried by rivers and streams

18. Abrasion by waves crashing onto rock break it down over time

19. Abrasion due to wind carrying sand (quartz) eroding rock

20. Sand-blasting graffiti off a brick wall using water, silica sand (quartz) and air pressure is an example of abrasion.

21. Abrasion due to glaciers: ice and rock fragments slide over bedrock scraping, scratching, polishing rock as it moves

22. Exfoliation (uploading)
As sedimentary rock erodes away, Igneous rock (granite) is uplifted and exposed.
With LESS PRESSURE (weight) on it, The granite breaks loose in layers (like an onion).

23. Uplift and exfoliation
What rock is this?

24. More exfoliated rock from Stone Mountain, Georgia
Ahhhh, I can finally relax, and expand with all that pressure off of me!

26. Biological Weathering
Plant roots grow into fractures and wedge the rocks apart as they grow.

27. Biological weathering
Mosses and lichens grow on rocks, slowly breaking them down over time.

28. Animals and insects burrow into soil thus exposing the bedrock to the elements

29. Human activity such as mining and construction blasting weathers rock.

30. Bell work ??????? What 4 ways does rock mechanically weather?
F______________ a. scraping, sand
A______________ b. plants, animals
E______________ c. freeze, expand
B _____________ d. peeling, pressure
Rost-wedging c.
Brasion a.
Xfoliation d.
Iological b.

31. Chemical Weathering
Rock is Decomposed (chemically changed) by agents such as
WATER: (hydrolysis) dissolves minerals in some rocks into ions.

32. Chemical weathering by water
Acids: weak carbonic acid formed when
(CO2 + rainwater = acid rain)
dissolves minerals, calcite (limestone and marble).
Sulfur dioxide an nitrogen compounds released from industries, produce acid rain that weathers structures made of concrete, stone and metal.

33. Which is made of granite and which is made of marble
Which is made of granite and which is made of marble? Which has been chemically weathered?

34. Oxygen: combines with metals to form oxides (such as iron oxide Fe2O3 or rust). This is called oxidation.

35. Caves and caverns are formed by dissolved minerals precipitating out of solution.

36. Factors that affect the Rate of Weathering
Not all rocks weather the same!
Name 4:
The minerals that compose the rock (hard vs. soft minerals)
2. How much surface area is exposed.
(small pieces weather faster)
3. The climate that the rock is in.
( temperature and precipitation)
4. TIME!
(more time – better)

37. Factor 1. Composition and Hardness weathering rate
Minerals that weather easily.
Feldspar
(breaks down into clay minerals – a major component in soils and shale)
olivine
Mica
Calcite
Gypsum
Marble rock
Minerals that resist weathering
Quartz (7 on Mohs hardness scale)
(ends up as sand on beaches)

38. Factor 2. Exposed surface area and weathering rate.
Rock that is broken into smaller pieces has more surface area that is exposed to weathering.

39. Factor 3. Climate and weathering rate.
Dry, cold climates
= s-l-o-w weathering
Warm, humid, wet climate
= rapid weathering

40. Bellwork Abrasion a. physical (mechanical) Rusting weathering
Exfoliation
Frost-wedging b. chemical weathering
Fizzing

41. Graph 1
Weathering of rock
Time

42. Graph 2
* granite?
* halite?
Mass of rock Chips
marble
Time

43. Graph 3
Rounding of rocks
Time in Water

44. Chemical Weathering (acid)
Graph 4
Amount of Quartz in the Rock
Calcite
Chemical Weathering (acid)
Quartz

45. Graph Part 1
Amount of Exposed Surface Area
Amount of Weathering

46. Graph Part 2 Hardness (Mohs) 1 talc 3 halite 10 diamond 7 quartz
Degree of Abrasion

47. Amount of Chemical Weathering (acid)
Graph Part 3
Amount of Calcite in the Rock
Amount of Chemical Weathering (acid)

48. Graph Part 4
Fe Concentration
Amount of Oxidation

49. Graph 5
Soil Production
Weathering of Rock