2. over long periods of timewithout obvious motion  Def: the breaking apart of rock over long periods of time and without obvious motion. ◦ Mechanical (Physical)- break into smaller pieces ◦ Chemical- chemical change in composition

3.  Weathering occurs at a slower rate than erosion.  Erosion involves obvious motion when breaking down rock

4.  Cause by water freezing  Common in high elevations and mid latitudes (Michigan)

10.  Removing overburden relieves pressure  Occurs mainly in intrusive igneous rocks ◦ batholiths

14. 3. Mudcracks  When water evaporates- mud shrinks  Wet/dry climates

17. Tree roots Growth breaks rock Lichen secrete acid dissolve rock  Humid climates  Usually sed. rock

18.  Change in composition (decomposition)

19.  Water + carbon dioxide = carbonic acid  H 2 O + CO 2 H 2 CO 3  Acid reacts (dissolves) with calcite (limestone, marble)  May create caves and sinkholes

25.  Marble statue

29. Cave Formation

33.  where iron minerals produce iron oxide ("rust"). Mafic rocks  Fe + O 2 (atm) Iron Oxide  Fe 2 O 3

36.  Hydrolysis  Reaction with water  feldspar + carbonic acid + water clay + soluble minerals  common in granite

37.  Water weathers the edges and creates a rounded shape  Aka onion skin weathering basalt

39.  Time- more time; more weathering  Rock Type/Resistance ◦ Sedimentary least resistant- esp. calcite  Climate ◦ Wet- chemical dominates ◦ Freeze/thaw- physical dominates  Surface area

41.  Smaller pieces (more surface area)= more weathering

42. Cleopatra’s Needle (Egypt) 3,000 years

43. Cleopatra’s Needle (New York) After 100 years

44.  Not all rocks weather equally

45.  Different rock types weather differently  OR  Different rates of weathering due to exposure