Transcript Weathering

• Chemical and/or Physical
breakdown of rock
Physical Weathering
• (mechanical)
• breakdown of rock
into smaller pieces
– Does not involve a
chemical change in
the rock
Frost Action/Wedging
• alternate freezing and thawing due to the
expansion of water when freezes =
potholes
b. Abrasion
– Rounding of rocks due to the rocks
hitting each other
c. Root Action
• Roots wedge and grow in rocks
d. Exfoliation
• Large sheets of loosened rock peel away
• http://arstechnica.com/science/2014/09/a-big-chunk-of-the-sierranevada-caught-fracturing-on-video/
Chemical Weathering
• Breakdown of rock due to a chemical
change in the rock
• Often requires water
• The higher the temperature, the faster the
chemical weathering
a. Oxidation
Iron + Oxygen
iron oxide,
(commonly called rust)
b. Carbonation
• Carbon dioxide + water = carbonic acid (in
rain) – a weak acid
• Slowly dissolves Limestone and Marble
Karst Topography
Caves
and
Sinkholes
• http://www.youtube.com/watch?v=tQvv8Y
FCGsY
• Karst and corvettes
• http://blog.hemmings.com/index.php/2014/
02/12/breaking-news-eight-cars-damagedby-sinkhole-at-the-national-corvettemuseum/?refer=news
c. Hydration
• Water plus other minerals
• Ex. Feldspar + water will slowly change
into clay
1. Particle Size/Surface Area
exposed at Surface
• The more surface area exposed, the
quicker the weathering
________
Why will smaller particles weather faster?
Which will weather faster and
why?
Pebbles
Sand
Silt
Clay
2. Mineral Composition
a. The harder the rock, the longer it
takes to break down
b. Calcite/Limestone >> dissolves in acidic
water
Which layer, X or Y is more resistant
to weathering? (resistant – harder to
weather)
Y, is hasn’t weathered as much
3. Climate
• A. Warm, moist climate >>>
• B. Moist with temperature variations of
freezing and thawing >>>