Download Weathering and Erosion

True or False: The Earth’s surface
has stayed the same for thousands of
years.
The Earth’s surface is always
changing!
▪ Weathering is the wearing down of rocks on Earth’s surface by wind,
water, and ice.
Here are some ways that weathering can occur…
1. Cool nights and hot days can cause rocks to crack open.
2. Water may seep into the cracks of rocks.
▪
If the water freezes, then the water expands, causing the cracks to be
larger and breaks the rocks apart.
▪
When the water melts and freezes again, it’s starts the whole process
over again.
3. Rain and running water can also break down rock into smaller
particles.
http://www.pbs.org/wgbh/nova/earth/how-caves-form.html
▪
Running water smoothes rock creating round stones and pebbles.
You can find these types of rock in streams and rivers.
4. Wind carrying sand and other particles can also wear down rocks
over time
Running water
Rain weathering
Running water
and wind
Wind
Rocks in a stream or river
that have been weathered
❖ What are some types of weathering that can wear down rock?
❖ Why do you think this process is called “WEATHERING”?
❖ Can you think of any examples of “weathering” that you can see
in your own community?
▪ Erosion- is the process by which weathered rock is moved away by wind, water, or
ice to a new location.
• As the wind blows, it picks up small particles of
sand/sediment and blasts large rocks with the
abrasive particles, cutting and shaping the rock.
• Wind is one of the most active agents of
erosion, especially in beaches, fields, and
deserts.
• Loose materials on the ground in these areas are
easily picked up by wind and can land anywhere.
• Water flowing in streams and rivers can also
break up rock and soil.
• The water in the streams and rivers then carry
these materials – known as sediment – to
another location.
http://www.bbc.co.uk/schools/riversandcoasts/coasts/change_coast/index.shtml
Sediment is sand pebbles, and other particles
moved by erosion and left in a new location
➢
• A fast-flowing river can gradually cut
through layers of rock, even creating a
beautiful canyon, like the Grand
Canyon.
➢Canyon- is a deep narrow valley
with steep sides often with a stream
running through it.
• The eroding rock has been carried
by the river to a new location.
Examples
of Erosion
http://www.classzone.com/books/earth_science/terc/con
tent/visualizations/es1205/es1205page01.cfm?chapter_no=
visualization
• Glaciers are rivers of ice.
•They form in places where there are very
cold winters and cool summers.
•The snow that falls in the winter does not
melt during the summer.
•Instead, the snow turns into ice.
✓New snow then falls on top of this ice.
✓As the layers of snow build up, the weight
of the snow increases, which then pushes
on the layers below causing glaciers.
•Glaciers move very slow, and as they
move, they scrape the Earth’s surface.
•Glaciers pick up loose rock, they can dig
holes, wear down mountains, and move rock
and soil.
•Glaciers can move millions of tons
of material, including boulders.
• To reduce soil erosion from water, wind, and rain, farmers
often plant trees, crops, or grass.
•The roots of the plant help hold the soil together against
wind and rain.
•Farmers also plow the land on hills in horizontal rows to
prevent fast-running rain water from falling straight
downwards and washing away topsoil.
❖ What is a glacier?
Life of a Glacier
http://www.pbs.org/wgbh/nova/vinson/glac-flash.html
❖ How do glaciers cause erosion?
❖ What examples of erosion can you find in your own
community?
Examples
of Erosion
http://www.classzone.com/books/earth_science/terc/con
tent/visualizations/es1205/es1205page01.cfm?chapter_no=
visualization
❑ Deposition- is the process by which the new rocks, soil, and other sediment moved
by erosion are left or deposited in a new place.
❑ Dunes are hills of sand most commonly found
on beaches and in dry inland areas where lakes
once existed.
❑ Winds blow the sand, creating hills with crests
or ridges.
❑ Deserts, like the Sahara in North Africa have
giant dunes made of wind-blown sand.
❑ Some dunes have been known to move such
as 50 feet a year.
❑ Waves carry sand and other sediment to the
shoreline, where they are deposited.
❑ This helps to create the many beautiful
beaches found throughout the world.
❑ Hurricanes can also destroy the beaches
carrying sediment to other locations and
depositing them elsewhere.
❑ Delta- is a area that forms where a river flows
into an ocean, sea, or lake.
❑ The river carries soil and other
sediment.
❑ Once the river reaches the
ocean or sea, its current stops.
❑The sediment it is carrying is
deposited at its mouth. This causes
the delta to gradually build up,
extending the land in a typical
triangle shape.
❑ Sometimes, spring rains cause a river,
creek, or stream to flood the area around it.
❑ When this occurs, the river leaves
behind a layer of mud and other
sediments.
❑ Gradually, these build up the floor of the
flood plain.
❑ The flood will leave deposits of mud on
the ground when it retreats.
❑ A glacial Moraine is material moved
by a glacier and then left when the
glacier retreats.
❑ It consists of the rocks, gravel, sand,
and soil scraped by the glacier form the
Earth’s surface.
❑ This material may have been carried
by the glacier on its surface or
underneath.
✓ Earth’s surface features are always changing.
✓ There are 3 important processes that SLOWLY change
Earth’s surface features:
1. Weathering
2. Erosion
3. Deposition
✓These processes are caused by the actions of water, wind, and
ice.
✓ Weathering- is the wearing down of rocks on the Earth’s
surface by wind, water, and ice.
✓ Weathering can be caused by water or ice seeping into the
cracks in rocks.
o Over time these cracks expand.
o The water in the cracks then freezes and eventually, the
rock breaks open.
✓ Rain and running water also help to break down rocks into
smaller particles.
✓ Erosion- is the process in which rock, soil, and sand are
broken down and moved away.
• Wind- can wear down rock and blow away sand and soil.
• Water- Streams and rivers break up rocks and soil and
carry then to a different location.
• Ice- Glaciers cause erosion by scraping the ground along its
path.
✓ Deposition- is the processes by which rocks, soil, and
other sediment are deposited in new places.
• Dunes- Hills of sand found in dry inland areas.
• Beach- Area of shoreline where waves have deposited
sand and sediment from the ocean.
• Deltas- Area formed by sediment where a river flow into an
ocean, sea, or lake.
• Flood Plain- Area built by layers of mud and sediment from
a flooding river.
•Glacial Moraine- Material left when a glacier retreats.