1. Weathering,Soil and Glacial Movement
Ch. 14,15

2. What Physical Properties Affect Rocks Near the Surface?
There are many processes that break rocks apart and can change their
color
texture
composition
strength
Called chemical and physical weathering

3. What is the role of joints in weathering
Joints are fractures in rock that are not offset.
Joints allow water and roots to penetrate the rocks to cause weathering.

4. Joints Closely spaced joints promote increased weathering.
Exfoliation- when overlying rocks are unloaded the underlying rocks expand creating expansion joints.

5. Physical Weathering Heating and cooling- expansion of rock
Frost wedging
Mineral wedging- growth of minerals weaken the rock around them

6. Physical Weathering cont
Burrowing organisms
Plant growth

7. Affect of Fracturing on Weathering
As a rock fractures and breaks apart there is an increase in the rate of weathering.
WHY??
As a rock breaks into smaller pieces the surface area increases allowing more exposure to weathering.

8. Chemical Weathering
Chemical factors that affect rocks at the earth’s surface
Decreased temperature and pressure
Increase O2
Increased H2O

9. Dissolving Rocks
Rocks are dissolved by weak acids formed in water that react with the minerals that make up rocks.
Acids are abundant in H+ ions, the H+ ions enter minerals releasing other ions
Ex- Limestone is rich in calcite which is soluble in weak acids. When Carbonic acid in rainwater reacts with the rock it dissolves.

10. Oxidizing Rocks
Free O2 is common near the surface and reacts with minerals to cause rust.
Most common in iron bearing minerals.
Mafic minerals commonly contain iron and are most commonly affected by oxidation.

11. How Does Water React With Minerals?
In some minerals water combines with the mineral causing formation of a new mineral, called hydrolysis.
If exposed to wet conditions many rocks convert into clay minerals.

12. How Does Soil Form
Soil consists of weathered rock, plus material from the atmosphere, decaying plants and microbes
Soil is made up of different zones, or horizons.

13. Soil Horizons O Horizon- surface accumulation of organic debris.
A Horizon- topsoil, dark gray or brown organic material mixed with minerals.
E Horizon- light colored, leached zone
B Horizon- little organic material, red color due to accumulation of iron oxide
C Horizon- weathered bedrock

14. Processes That Occur During Soil Formation
Soil forms over thousands of years as a result of weathering.
Involves the vertical movement of dissolved material up and down through the horizons.

15. How Materials Move Through Soil
Materials move both up and down as carried by water, animals and gravity
Zone of leaching- Upper part of soil loses material downward. Water leaches soluble materials and carries them downward.
Zone of Accumulation- Chemical ions leached from above accumulate in the lower levels.

17. Glaciers Moving masses of ice.
They form by the accumulation of snow and ice.
Average amount of incoming snowfall > amount lost by melting and evaporation
Blue color because there is less air.

18. Glacier Movement
Glaciers move downhill because ice is not strong enough to support its own weight.
Shearing force – the top of the glacier moves faster than the bottom because of friction.

19. Glacial movement continued
As glaciers move internal stress causes the upper surface of ice to break forming fractures, called crevasses.
When the glacier reaches water, it will float.
When glaciers break off, in a process called calving, they float off as icebergs.

20. Glacial Rebound
the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostasy.
2 phases
Initial uplift called elastic- rapid
Slow viscous flow- ~1cm/year