1. By Gravity, Wind, and Water
Weathering & Erosion
By Gravity, Wind, and Water

2. What is “weathering?”
Weathering is the break down of rocks that have been exposed to the atmosphere
Chemical Weathering
rocks break down as their minerals change in composition (they become different substances)
Physical Weathering
rocks are broken down into smaller pieces without changing their composition

3. Factors which affect the rate of weathering:
1.)The amount of material exposed
* greater surface area= more weathering
2.) Particle Size- smaller particles= more surface area
3.)Climate-
*Chemical weathering: hot & wet *Physical weathering: cold or warm and dry, alternating cold and cool & wet (Frost Action)
4.) Mineral Composition:
-Chemical: some minerals react with acid
-Physical: Some minerals are more durable/ have a greater hardness

5. small particles (high surface area)=fast weathering
*small particles (high surface area)=fast weathering *Large particles (low surf. area)= slow weathering

6. Physical or Chemical Weathering dominant in an area depends upon its climate

7. Types of Physical Weathering:
1.)Ice wedging/frost action
water enters small cracks in the rock
Water freezes expands forces the cracks to open more
repeats until the rock breaks apart

8. 2.) Wetting and drying
breaks up rocks made from clay
When wet they expand, and as they dry they shrink
As this repeats over and over, the clay becomes weak and cracks

9. 3.) Exfoliation or “Unloading”
-when rocks are uplifted
and exposed the pressure on them ↓
-rock surface then expands and “sheds” its layers

10. 4.) Plant Growth Root wedging from trees
Lichens and Moss break apart surface of rock

11. 5.) Abrasion by Water: tumbling  Spheroidal pebbles
Water carries sediments and tumbles them eventually making them smooth

12. 6.) Abrasion by Wind
Arid regions with little or no vegetation carry airborne sediments in wind currents which over time smash and erode the rock surface

14. Chemical Weathering 1.) Oxidation
oxygen reacts with some minerals, especially those containing iron (magnetite) to form rust (called iron oxide)

15. 2.)Carbonic Acid aka “Acid Rain”
Water in atm. mixes with CO2 to form weak acids

16. Rocks/ Minerals that weather with acid:
1.) Calcite (mineral)
2.) Limestone (made of calcite)
3.) Marble (made of calcite)

17. Weathering from Carbonic Acid also creates caves and sinkholes
Weathering from Carbonic Acid also creates caves and sinkholes. These areas are referred to as “Karst” topography

18. Looking at karst topography from the surface (you can see the rock dissolved along the joints)

21. Calcium Deposits (Stalactites and Stalagmites!)

22. When enough of the limestone is dissolved under the ground, it will collapse forming a sinkhole! Man killed in Sink Hole News Clip

23. Anywhere that’s underlain by large volumes of limestone is a risky area to build on

24. 3.) Natural Acids: Organic Acid from decaying plants in soil
Sulfuric Acid from volcanic activity/hot springs

25. 4.) Hydrolosis
water (hydro) reacts with minerals such as feldsparforms clay

26. ROCKS VARY IN RESISTANCE TO WEATHERING

27. The more resistant rock will be eroded less than the weaker ones

28. And the weaker ones more…

29. Devils Tower, Wyoming
All that remains of this ancient volcano is the central “plug” of solidified and very weather-resistant igneous rock

30. EROSION PART II
Erosion is the TRANSPORT of weathered materials!

31. Part II: AGENTS OF EROSION
These are the forces or materials that transport or move sediments:
Gravity
Wind
Running water (streams/ rivers)
Glaciers
Waves

32. Erosion by Gravity (the most powerful one!)
When gravitational force is greater than the force friction of the land, movement occurs!
These are called Mass Movements
-Soil creep -Avalanches
-landslides -Pyroclastic
-Mudflows -Rock falls

33. Evidence of Soil Creep

34. Mass Movements Video Links Click Below: Rock Slide in TN
Mudslide in Afghanistan
Avalanche in Alps

35. 2.) Wind Erosion aka Abrasion/Deflation *Dependent on: Wind Velocity*
* . As sediment size _________, the amount of erosion by wind _________. (because lighter to carry)

36. 3.) Water
*The faster water flows, the heavier and larger objects it can erode and transport

37. The greater the velocity, the larger the particle diameter it can carry! Q: at what velocity can pebble size particles be transported? If it is under this, it will be deposited!

38. Because of variations in velocity, there is deposition & erosion in different areas along a river
This means river profiles differ according to the velocity
*A stream is deepest where the current is the fastest

40. 4.) Erosion and Deposition by Ocean Currents and Waves
Surface ocean currents and waves are generated mostly by wind.
Wave action
Energy within a wave is propagated through a transverse wave
Circular motion within a wave results in the movement of sediments

41. Circular motion in a wave
Wave action animation

42. As waves crash into the shoreline, they erode the bedrock animation

43. Erosion of sand from areas causes deposition in others: Longshore Currents
Beach
Deposition of sediments by ocean waves
Sand Bars
Sediments deposited by long shore currents
Barrier Islands
Large sandbars

44. NY Barrier Islands: South Short of Long Island!

46. Long Beach Long Island NY