Transcript Mechanical Weathering Notes Power Point

Weathering
• The breakdown do the materials of Earth’s
crust into smaller pieces.
http://vle.whs.bucks.sch.uk/course/view.ph
p?id=3204
Mechanical
Weathering
Photo A
Photo B
Abrasion
• The grinding and
wearing away of
rock surfaces
through the
mechanical action
of other rock or
sand particles.
• Caused by wind,
water, & gravity.
http://geology.com/rock-tumbler/rocktumbler-grit.shtml
TUMBLING GRIT:
Silicon Carbonate is
harder than the
rocks you are
tumbling and will
therefore smooth off
the rough edges.
http://geology.com/rock-tumbler/rocktumbler-grit.shtml
http://geology.com/rock-tumbler/rock-tumbler-grit.shtml
Rocks before they
are tumbled..
And after they are
tumbled.
http://geology.com/rock-tumbler/rocktumbler-grit.shtml
How did the pebbles get this way? Why
are they not sharp?
Flowing Water
As rocks and pebbles
roll along the bottom
of flowing water, they
bump and scrape
against each other,
causing these rocks
to become rounded
and smooth.
2. Water
• River carries rocks
and pebbles that
bump and scrape
against each other,
eventually wearing
them down. (This
makes them
smooth &
rounded).
National Geographic Photos
WIND
wind blows sand and silt
against exposed rock
eventually wearing away
the rock’s surface.
3. Wind
• Blows and silt
across exposed
rock, wearing
down the rock’s
surface.
http://www.cbc.ca/news/canada/british-columbia/story/2008/07/30/bc-highway-rockslide-whistler.html
3. Gravity
• Rocks pulled
down and falling
on top of each
other
–Ex. Rockslide
(rocks falling
down a
mountain or
cliff)
GRAVITY
Rocks grind against
each other during a
rock slide, creating
smaller and smaller
rock fragments.
Anytime one rock hits
another rock, abrasion
takes place.
Frost Wedging
Frost Heaving
ICE
• Water seeps into
cracks during warm
weather.
• When the
temperature drops,
the water freezes
and expands, causing
the ice to push against
the sides of the crack.
* This causes the
crack in the rock to
widen.
5. Plants
• Roots grow into
cracks in the rocks.
As the roots grow,
they press on sides
& break apart the
rock
–Ex. Tree roots
breaking up
sidewalk
PLANTS
The roots grow through
existing cracks in rocks. The
growth causes the root to
expand, forcing the crack to
widen. The force can
eventually split the rock
apart.
6. Animals
• Burrowing animals
loosen sediment &
push it to the
surface. This
exposes it to other
forces of
weathering.
• Ex. Rabbits, worms,
ants, coyotes, &
mice
Animals
Animals that live in the soil
(moles, prairie dogs,
insects, worms, gophers),
cause a lot of weathering.
By burrowing in the ground,
these living creatures brake
up soil and loosen rocks to
be exposed to further
weathering
Question Time
1. For each question, tell what type of
mechanical weathering is happening.
2. Write on dry erase board the agent
causing the weathering.
3. Discuss with your partner & explain how
that agent caused what you see in the
picture.
What agent of mechanical weathering is at
work here?
Flowing Water
As rocks and pebbles
roll along the bottom
of flowing water, they
bump and scrape
against each other,
causing these rocks
to become rounded
and smooth.
What agent of mechanical weathering is at
work here?
WIND
wind blows sand and silt
against exposed rock
eventually wearing away
the rock’s surface.
What agent of mechanical weathering is at
work here?
What agent of mechanical weathering is at
work here?
ICE
Water seeps into cracks
during warm weather.
When the temperature
drops, the water
freezes and expands,
causing the ice to push
against the sides of the
crack. This causes the
crack in the rock to
widen.
Ice- Wedging
What agent of mechanical weathering is at
work here?
Animals
Animals that live in the soil
(moles, prairie dogs,
insects, worms, gophers),
cause a lot of weathering.
By burrowing in the ground,
these living creatures brake
up soil and loosen rocks to
be exposed to further
weathering
Animals
What agent of mechanical weathering is at
work here?
PLANTS
The roots grow through
existing cracks in rocks. The
growth causes the root to
expand, forcing the crack to
widen. The force can
eventually split the rock
apart.
Temperature Change
Cold causes rock to contract
(shrink).
Heat causes rock to expand
(grow slightly).
Demos:
https://sites.google.com/site/sed695b/project
s/demonstration-equipment/expanding-ball-ring--thermal-expansion
https://www.youtube.com/watch?v=hX2Y2IDj
uGI
Plants