Transcript Changes in the Earth`s Surface

What’s Wrong With This Picture?
Take a minute to write
down a list of what you
think is wrong with these
statues!
Changes in the Earth’s
Surface
Chapter 1.3
Weathering & Erosion
(Forces that change the Earth
over a period of time….)
Weathering
 Weathering:
Breakdown of rock at or
near the earth’s surface into smaller
pieces.
*2 Kinds of Weathering:
*Mechanical Weathering
*Chemical Weathering
Mechanical Weathering
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Rock is broken/weakened
physically
Frost Wedging: water freezes
to ice in cracked rock, the ice
expands and creates a bigger
crack.
Seeds taking root in cracked
rock.
Over time these types of
weathering can cause huge
parts of mountainside to
break and fall away!!
Chemical Weathering
 Mechanical
weathering changes the
structure of a rock, CHEMICAL
weathering alters the rock’s chemical
makeup
 Can change one kind of rock into
another
 Water and Carbon Dioxide (air, soil)when mixed =Carbonic acid
Chemical Change
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The acidic water seeps into
cracks (i.e.Limestone) and
dissolves rock.
Acid Rain: Chemicals in the
polluted air combine with
water vapor and fall as acid
rain.
Acid rain destroys forests,
pollutes water, & eats away at
the surfaces of buildings
Limestone Caves
Erosion


Movement of weathered
materials such as gravel, soil,
and sand.
3 Common Causes of Erosion:
*Water
*Wind
*Glaciers
Water
Largest canyons/deepest valleys created in part
by moving water (rain, rivers, streams,
oceans)
 Water = Greatest cause of erosion.
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Water carries sediment (small particles of
soil/sand/gravel) which helps grind away
surface rocks in the water’s path!
Sediment is eventually deposited (i.e.
Mississippi River carries 159 million tons of
sediment per year!)
Water Erosion-Devastating Effects
FLOODING: Can occur when:
 heavy, intense rainfall
 run-off from a deep snow
cover
 over-saturated soil, when
the ground can't hold
anymore water.
*Flooding causes erosion of
the land and other physical
characteristics.
*Flooding also destroys
private/public property and
endangers lives.
New Orleans
Wave Action = Erosion
Historic New England Floods
http://www.pbs.org/wgbh/amex/hurricane38/sfeature/
sf_footage.html (Video Clip)
Houses were built on shifting sand, too close to the
sea. Bridges were too flimsy, roads too low. When the
September hurricane struck it brought massive
flooding, one resident said, "It was your worst
nightmare coming true.“
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In the storm's aftermath, city streets became surreal
junkyards full of debris, traveled by looters in
rowboats. Entire beach communities disappeared.
Thousands of livestock were killed. New England lost
275 million trees, including a third of Vermont's sugar
maples. And hundreds of people died.
WIND
2nd Major Cause of
Erosion (esp. in areas
with little water).
 Loess
 Sandstorms
 Dust Bowl 1930’s

(Video Clip)
http://www.livinghistoryf
arm.org/farminginthe3
0s/water_02.html
Glaciers
 Glaciers:
Huge, slow-moving sheets
of ice (form over years of unmelted
snow pressed together, thaw slightly,
and then turn to ice)
 When
glaciers move they carry dirt,
rocks, and boulders. The glacier
wears away the terrain in its path.
Glaciers: The Impact
 Glaciers
move (slide forward) due to
their great weight carve U-shaped
 Basins
of the Great Lakes
 Moraines: ridge-like piles of rocks
and debris left behind melted
glaciers.
 Long ridges of land (Long Island)
Icebergs