Transcript Slide 1 - Images

What is weathering?
Rocks on the Earth’s
surface undergoing
changes in appearance
and composition
What are the 2 types of
Weathering?
1. Mechanicalphysically changing rock into
smaller pieces without changing its
composition
2. Chemicallybreakdown of rock by changing its
chemical composition
Types of Mechanical
Weathering
1. Exfoliation
(unloading)- process
where sheets of rock
peel or flake away
Example of exfoliation:
Types of Mechanical
Weathering
weathering
2. Ice wedge- occurs
when water seeps into
rocks and freezes
Ice
wedging
Types of Mechanical
Weathering
weathering
3. Biological activity- the
activity of organisms,
including plants, burrowing
animals, and humans that
weather away rock
Weathering by plants
Weathering by sandmartins
nesting in cliff
Types of Mechanical
Weathering
weathering
4. Abrasion- collision of
rock with one another
resulting in breaking
and wearing away.
• Abrasion takes place in many
environments:
– fast-moving streams
– beaches subject to storm waves
– desert environments with high winds
– beneath glaciers that are loaded
with fragments of rock.
Water-carried particles
eating away at the rock
Storm waves have eaten
away at the shoreline
The ocean waves have eroded
this beach leaving behind a
cliff as the soil was washed
away
Observe the effects of
mechanical
weathering.
Types of Chemical
Weathering
1. Hydrolysis:
Change in composition
of minerals when they
react with water
Feldspar combines with H2O to
form a common clay called kaolin
Types of Chemical
Weathering
2. Carbonation –
When some minerals come
in contact with carbonic
acid, they form a new
product
Stalactites caused by
carbonation
Limestone
is eaten
away by
acid and
deposits as
it drips
from ceiling
of cavern
Types of Chemical
Weathering
3. Oxidation –
When metallic elements
combine with oxygen
Oxidation =
rust!
Types of Chemical
Weathering
4. Acid
Precipitation
“acid rain”
Types of Chemical
Weathering
5. Plant acids – plants
secrete acids that
erode away the rock
Lichens and
mosses grow
on rocks and
secrete
weak acids
that dissolve
the surface
What 4 things
affect the
rate of
weathering?
1. Rock composition
• Igneous and
metamorphic rocks
don’t weather easily
• Sedimentary rocks do
2. Amount of exposure
• More exposure it receives,
faster it will weather
• Amount of time and
amount of surface area
exposed is also important
3. Climate
• Slow in very hot / very
cold climates
• Fairly rapid in warm,
humid climates
Cleopatra’s needle after only
one century in New York City
4. Topography
• Elevation or slope of
surface where rock is
located affects rate of
weathering