Transcript What is a CHEMICAL change?

*
DO NOW:
*What is a PHYSICAL change?
*What is a CHEMICAL change?
Weathering- the process that breaks down rocks into smaller
fragments- resulting in soil.
Rates of weathering are affected by:
1. Surface area-when more is exposed, more weathering occurs.
Rates of weathering are affected by
2. Rock composition- less resistant rocks weather faster.
Rates of weathering are affected by
3.CLIMATE- rocks weather (chemically) faster in hot humid climates
Sinkholes in Guatamala
TYPES OF WEATHERING
1.Mechanical Weathering- (disintegration)
breaks rocks without changing the
chemical composition.
a. Abrasion- breaking up of rocks as
they rub against each other
b. Biologic activity
Root wedging- roots from plants grow and
break rock
Have you ever tripped over a sidewalk like this?
Animals burrow
creating more surface
area available for
weathering to affect
c. Frost wedging- water seeps into cracks in rock and
expands breaking it
A pot hole is an example of frost
wedging
Exfoliation or upward
expansionigneous intrusions (domes)
are exposed and expand from
lack of pressure.
<- Agents of Erosion
(wind, running water riVers, wave action, glaciers, mass wasting) weather
and move layers of sedimentary rock
2. Chemical Weathering (decomposition)- changes molecular
structure of rock, making entirely different products.
a. Oxidation- when oxygen unites chemically with minerals in
rock (ex) rust
b. Hydration- water unites chemically with minerals in rocks –
sometimes makes clay.
c. Carbonation- carbon dioxide unites chemically with minerals
in rocks.
Carbon dioxide + water = carbonic acid
which dissolves rocks!
CO2
Oh no!
Slightly
Acidic
Rain!
d. Biologic Activity:
Hey,
I’m a fun guy!
Lichens, mosses, fungi,
and enzymes on tree
roots can decompose
rock
CaCO3 + 2 CH3COOH => Ca(CH3COO)2 + CO2 + H2O
Calcium
Carbonate
(chalk)
+
Acetic Acid
(vinegar)
=>
Calcium
acetate
(That white stuff on
the blue)
+
Carbon
Dioxide
(The bubbles you saw
in the beginning of the
experiment)
+
Water
(The reason the chalk looks
wet)
The Great Chalk Experiment
*N TICE* You can’t get something
from nothing!
http://www.yteach.co.uk/page.php/resources/view_all?id=limestone_chalk_marble_rock_water_dissolution_carbonate_mortar_cement_concrete_page_1&from=search
Remember
this?
"Cleopatra's Needle”:
Obelisk built in 1443 BCE.
It was erected first at
Heliopolis, Egypt, and
moved to Alexandria in 12
BCE by the Romans.
Later, presented to the City
of New York by the Khedive
of Egypt in 1879, and
erected in Central Park
early in 1881.
Pink granite; 69 ft. x 8 ft. 21
meters high and weighs
about 180 tons.)
Hmmmm….
Why are they different?
Chemical weathering of chalk bedrock in England.
Sinkholes: http://youtu.be/tQvv8YFCGsY
Infiltration
happens
http://www.teachersdomain.org/asset/ket09_vid_karst/
What is Erosion?
WIND
-
gravity
Glaciers
http://youtu.be/XAYhNHhxN0A
Coastal
processes
Rivers
The MOVEMENT of (weathered) sediment by wind, water,
ice or gravity which wears away or lowers Earth’s land
surfaces. *Erosion is NOT weathering!
What is the
result of
weathering
and erosion?
A mature soil profile
Sediment
Transported soil- was brought by an agent of erosion.
Residual soil- weathered native bedrock
What is Deposition ?
Deposition is the geological process in which
sediments, soil and rocks are added to a landform
or land mass.
+
When wind, waves, glaciers, and gravity lose carrying power,
particles are dropped onto the surface of the land.
When the river meets the sea= delta
When running water meets a shallower slope, it drops the
heaviest particles first.
Horizontal Sorting
x
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0604/es0604page01.cfm?chapter_no=visualization
When the river meets the land= alluvial fan
Why is the
surrounding
area so fertile?
Factors affecting deposition in
still water:
1. Particle size- larger particles will settle faster.
2. Particle shape- round particles will settle faster
than flat ones.
3. Particle density- higher density particles settle
first.
Vertical Sorting:
The number
of layers tells
how many
depositional
events
occurred.
http://hmxearthscience.com/Warehouse/geology/surface_processes/animation
s/settling.swf
Types of sorting
When Weathering and Erosion (-)
=
Deposition (+)
the landscape is in
DYNAMIC EQUILIBRIUM
The End!
How are your notes?