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)

11.  Removing overburden relieves pressure  Outer layer peels off like onion skin  Occurs mainly in intrusive igneous rocks ◦ batholiths

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

16. Lichen secrete acid dissolve rock Tree roots- growth breaks rocks  Humid climates  Usually sed. rock

17.  Change in composition (decomposition)

18.  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

27.  Marble statue

31.  where iron minerals produce iron oxide ("rust").  Often in ss from iron in groundwater OR mafic rocks  Fe + O 2 (atm) Iron Oxide  Fe 2 O 3

34.  Hydrolysis  Reaction with water  feldspar + carbonic acid +water clay + salt  common in granite  Result- holes in granite

35.  Water enters cracks in rock and weathers the edges and creates a rounded shape  Any rock type  Result- rounded spheres t

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

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

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

41. Cleopatra’s Needle (New York)  100 years old

42.  Not all rocks weather equally

43.  Different rock types weather differently  OR  Different rates of weathering due to cracks

46. limestone shale

48.  Tall spires of rock  Often “balancing”  Softer rock (shale) erodes faster than cap rock

50.  Thoughts?