Transcript So even though the two mountain areas are very similar landforms

Land has many different shapes.
 A natural land shape or feature is called
a landform.
 When you describe the landforms
around your town you are describing
topography.
 Topography is all the kinds of different
landform in a certain area.
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These are the Rocky
Mountains.
This is a tall, jagged
peak mountain that
rises thousands of
feet above the
Surrounding land.
The Appalachian
Mountains in this
picture are lower
and more rounded.
They are still
thousands of feet
tall, but are much
lower than the rocky mountains.
So even though the two
mountain areas are very similar
landforms, their topographies
are very different!
The topography of volcanoes
differs in another way.
Volcanoes usually occur as
individual mountains, not in
ranges. They may have steep
sides or rounded slopes.
Hills are landforms that
are like mountains, but
not as high.
Most hills have
rounded slopes.
 Not
all landforms have slopes.
 A plain is a large, flat landform
with little relief.
 Relief is the difference in
elevation between high and
low places.
Glaciers are large
sheets of ice.
 As they move, they
change the land
beneath and
around them.
 Moraines are long,
low hills formed by
glaciers.
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As moving ice
scrapes the land
beneath it, rocks
and other
materials are
picked up and
carried away.
 This material is
deposited
somewhere else,
when the glacier
melts.
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Q. How can you tell a
moraine from a hill
Moraines have rock, sand,
and clay.
These things are deposited
together.
Other landforms made by
glaciers are glacial
grooves.
Glacial grooves are scrapes
and scratches in the rock
made as the glacier
moves along land.
Landforms of sand are
easily shaped by wind
and water.
 These landforms are
known as sand dunes.
 Wind can change a
sand dunes shape or
even it’s entire
location.
 Sand dunes can move
as much as 100 ft. in
one year.
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Water also reshapes
beaches, forming
barrier islands and san
spits extending out
into the water from the
ends of many islands.
 Sand spits and barrier
islands are long,
narrow piles of sand
that help protect the
mainland from the
wave erosion.
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A mesa is a tall, flat-topped
rock feature, that forms
when water and wind
erodes the surrounding rock.
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Canyons are deep valleys
with steep sides. They are
found throughout the
Southwest. The water and
wind has carved the land
away. The Grand Canyon is
an example.
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Over time, sand wears away rock by
breaking it into smaller pieces.
This process is known as weathering.
Step 1: Weathered rock (sand) is carried
away by wind.
Step 2: The pieces keep moving as long as
the wind is blowing.
Step 3: The wind stops and the sand falls to
the ground.
Step 4: These piles grow.
Step 5: They slowly become sand dunes.
Are found in many places:
deserts, beaches,
lakeshores, etc.
 Some desert dunes are as
high as a 30-story building.
 All dunes help protect
land during storms.
 However, dunes can
cause damage to
buildings and roads if
pushed by strong winds.
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Moving water can change
Earth’s surface by carrying
soil and small pieces of
rock away from landforms.
Moving water can dig a
canyon or change the
path of a river.
A rapidly flowing river
erodes its banks and its
bottom.
Eroding banks makes the
river wider.
Eroding the bottom makes
the river deeper.
The moving water
then carries sediment
downstream.
 When the water slows
down, sediment is
deposited.
 Deposits on a river
bank, makes it
narrower.
 Deposits in the
bottom make the river
shallower.
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Moving wind and water has
energy.
The faster it moves, the more
energy it has.
But, all moving water, even a
gentle rain, can erode some
sediment.
When rain falls on bare soil, it
splashes away soil.
As it runs downhill, it gains speed
and energy.
Over time, water erosion can
leave gullies, or ditches in the
ground.
Ocean waves also
cause erosion.
 Waves carry away
broken bits of rock and
sand.
 Piece by piece, cliffs get
steeper.
 When cliffs eventually
overhang, the entire cliff
can collapse into the
oceans.
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Ocean waves change
landforms in another
way, also.
 Each wave also brings
more sand to the
beach.
 This is deposition.
 As the water slows
down, it loses energy
and the larger pieces of
sediment fall out and
settle to the bottom.
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Flooding can deposit
sediment near a river.
When you have heavy rains,
rivers flood their banks.
When the rain stops, the
water returns, but the
sediment it carried is
deposited on the land.
This sediment is rich in
nutrients for plants.
These areas are called flood
plains and are great for
farmers, but awful for living.
Rivers deposit sediment at
the mouth, the place
where it empties into the
ocean.
 The flow of water slows as
the river reaches the
ocean.
 Much sediment is
deposited, forming a delta.
 A delta is an area of new
land at the mouth of the
river.
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Ground water can weather
and erode soft rocks.
Underground erosion
causes caves to form.
If the roof of the cave
collapses, under the weight,
it creates a large hole.
These holes are Sink Holes.
Most sinkholes are found
where limestone is
common.
Gravity also helps
land-changing
processes to occur.
 Landslides happen
very suddenly,
especially after heavy
rains or earthquakes.
 A land slide is when
soil, mud, and rock
move quickly down a
slope.
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Ice can change landforms by
weathering rocks.
Rocks have tiny cracks and
holes
When it rains, these fill with
water.
If it is cold the water freezes,
and expands, making cracks
bigger.
The next time it rains, more
water gets in, and the process
continues.
Over time, the rocks are broken
into smaller pieces, until there is
only a pile of sand.
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Ice can also change
landforms as glaciers.
Glaciers can shape
landforms by erosion and
deposition.
Glaciers follow river
valleys down a mountain.
As a glacier moves, it
changes the V-shaped
valley into a U-shaped
valley.
Glaciers deposit the
sediment when they melt.
New York is an island
formed from the
deposition of a glacier.
Plants can cause
weathering and erosion.
 When a seed germinates
on a rock, the roots grow
in small cracks.
 As the roots grow they
cause the cracks to
grow.
 Some plants even
release chemicals into
the soil.
 These chemicals help
weather rock by
dissolving certain
minerals.
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Plants also preserve and
protect Earth’s
landforms.
 Roots hold soil and sand
in place, and prevent
erosion by wind and
water.
 Farmers often plant
cover crops, to help
return nutrients to the
soil and stop erosion.
 At the beaches, plans
keep sand dunes from
blowing away.
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The center of the Earth is 4000 miles
down.
 The Earth has 4 layers 1. crust
 2. mantle
 3. outer core
 4. inner core.
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The Crust is solid rock.
 The Mantle is also a
lot of solid rock, but
there is also soft rock,
like melted candy.
 The Outer Core is
liquid iron (not rock),
and is liquid.
 The Inner Core is iron
and nickel, and is
solid due to great
pressure.
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The Earth’s crust is
divided into plates.
Plates are puzzle
pieces that fit
together.
There are 10 major
plates.
Plates “float” on the
mantle.
As the rock flows, the
plates move.
This causes changes in
the Earth.
When 2 plates
move past each
other, energy is
released and the
ground shakes.
 An earthquake is
movement of the
ground caused by
a sudden release
of energy in
Earth’s crust.
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The place within the crust
where the energy is released
is called the focus.
The greatest damage will
occur directly above the
focus.
The point on the Earth’s
surface that is directly
above the focus is called
the epicenter.
Earth quakes are caused by
3 types of plate movement:
1. plates pushing together
2.plates sliding past each
other
3. plates pulling apart
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Earthquakes occur along a fault, or break in
the crust.
Most faults are found near the edges of
plates.
Faults develop as plate movement bends
and cracks the crust.
Earthquakes caused by pushing plates are
strong.
Earthquakes caused by pulling plates are
weak.
Earthquakes are measured by their
magnitude, or amount of energy released.
It is reported on the Richter Scale.
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An earthquake
measuring 2.0
is too small to
be felt.
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An earthquake
measuring 6.0
or more can
cause a lot of
damage.
Melted rock beneath the
surface of the Earth is magma.
 Magma forms in places where
plates push against or pull away
from each other.
 Magma is less dense than solid
rock, so it pushes upward.
 A vent is an opening in the crust
where magma can come out.
 When magma reaches the air, it
is called lava.
 A volcano is a mountain made
of lava, ash, or other materials
from eruptions.
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Composite Volcanoeswide with steep slopes.
Made of alternating
layers of lava and ash.
(Mt. St. Helens)
Shield Volcanoes-broad
with gentle slopes. Form
from lava that easily
vents. (Hawaiian Islands)
Cinder Cone Volcanoestall and narrow, steep
slopes. Made of rock,
ash and other materials.
Are not made of lava.
(Paricutin)
Mountains are the
tallest landforms.
 They form where the
crust is crumpled and
pushed up.
 The edge of the denser
plate sinks, and the less
dense plate pushes up.
 If they are the same
density they both push
up.
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