Transcript Section Nine Earth Science Landforms and Changes to

Section Nine
Earth Science
Landforms and Changes to
Earth’s Surface
Landforms
The surface of Earth is covered with a variety of different types of
landforms.
valley
mountains
island
desert
canyon
delta
plain
coastline
volcano
Changes to Earth’s Surface
• The surface of Earth is
always changing.
Changes can be slow
or fast.
• Changes can break
down or wear away
landforms.
• Changes can also build
up or create new land.
Weathering
•
•
•
•
Weathering is the
process by which rocks
are broken down into
smaller pieces.
Weathering is mainly
caused by wind, water and
ice.
Plants, temperature
changes, and animals can
cause weathering too.
Weathering is a slow
process and the result of
weathering is smoother
rocks or rock formations
gradually getting smaller.
Erosion and Deposition
• Erosion is the
movement of rocks,
soil, and sand to a
new place.
• Erosion is caused by
wind, water, ice and
gravity.
• After the Earth
materials are moved
by erosion, they are
dropped in a new
spot, which is called
deposition.
Land Formed by Erosion and
Deposition.
• As rivers flow, they pick
up and carry a great deal
of soil, rocks and sand.
• At the mouth (end) the
river will normally slow
down, widen, and empty
into a larger body of
water like a gulf or
ocean. When this
happens it deposits all of
the materials it was
carrying.
• This deposition forms
new land called a delta.
Land Changed by Erosion
and Deposition.
• Glaciers are ice masses.
They move like a slow
flowing river.
• Underneath a glacier
where the ice meets the
ground, large amounts of
soil and rock are crushed
and ground apart.
• Glaciers transport
(move) and deposit the
materials beneath them
in new places.
• Glaciers also carve away
the land beneath them
making valleys.
Formation of Caves
• A cave is a natural
opening usually in
rock. Caves form when
water seeps into the
ground and wears
away rock beneath the
surface.
• The water that seeps
through can carry
minerals that slowly
build up and create
stalactites from cave
ceilings or stalagmites
on cave floors.
Tectonic Plate Movement
• Sections of the Earth
called plates float
and move on top of
the mantle of the
Earth.
• The plates are
always moving and
sometimes their
movements cause
earthquakes or
volcanoes.
Earthquakes
• The edges where the
plates touch is called a
fault.
• As plates move, they
sometimes slide or rub
against each other.
• If they can’t slide easily,
pressure will build up in
the spots where they
touch.
• When one plate finally
pushes past another, the
pressure is released and
the ground shakes
causing an earthquake.
Volcanoes
• Volcanoes occur mainly in
areas where one plate
pushes under another.
• When a volcano erupts,
magma (molten rock)
pushes its way up to the
Earth’s surface.
• Magma on the Earth’s
surface is called lava.
• Lava will cool and create
new land around the
volcano’s crater.
Changes to Earth’s
Surface Questions
1. Rivers carry a great deal of sediment (rocks, sand, and soil) as they flow.
When a river enters a larger body of water it slows and can drop the
sediment. What landform is likely to be created from the sediment?
A.
B.
C.
D.
canyon
delta
island
coast
2. What is most responsible for this sea arch?
A.
B.
C.
D.
Plate tectonics
Earthquakes
Erosion
Deposition
3. How do plants most commonly break large rocks into smaller pieces?
A. Plant leaves conduct heat from the sun which they pass to surrounding
rocks.
B. Plant roots grow into cracks in rocks.
C. Seed from plants fall into rocks and release acids
D. Stems of plants surround and squeeze rocks.
4. When volcanoes erupt magma flows out of the crater onto to the
Earth’s surface as lava. What is a likely to happen to the Earth’s surface
after a volcanic eruption?
A. New land is formed when the lava cools and hardens.
B. There is no change to the Earth’s surface.
C. The land surrounding the volcano will be lower than before.
D. The lava will help enrich the soil so the trees and plants
grow better..
5. Which of the following can be caused by weathering?
A.
B.
C.
D.
cracks forming in a boulder
rocks melting to form magma
glaciers forming on a mountainside
pebbles combining to form a large rock
Answers and Explanations
1. B – when a river deposits rocks, soil, and sand as it
enters a body of water, the deposited materials will most
likely form a delta.
2. C – the waves are most responsible for causing the
erosion that wears away the rock in the sea arch
3. B – the most common way that plants break apart rocks
happens when the roots of plants grow into cracks in the
rocks
4. A – the most likely result of volcanic eruptions is the
build up of new land
5. A – weathering is the breaking apart of rocks, and when
rocks (like boulders) heat up from the sun shining on them
and cool down at night, they can begin to form cracks
which can cause them to weather (break apart)