Transcript Landforms and Oceans

Constructive and
Destructive Forces
that effect Earth’s
Landforms
Weathering
Weathering is the process that breaks down rocks
at or near the surface of the earth.
 Weathering can be either physical or chemical.
 These processes cause the surface of the earth to
dissolve, decompose, and break into smaller pieces.
Weathering cont….
 Water is an important cause of weathering.
 Plants cause weathering when roots break apart rock. (physical)
 Changes in temperature can break rock, as well as ice forming
inside cracks in the rock causing it to break even more.
 Anything that causes rocks to wear down or break apart is a cause
of weathering.
Erosion
•Erosion is the movement of sediments
and soil by wind, water, ice, and gravity.
Deposition
Deposition is the dropping, or depositing, of sediments
(soil, sand and minerals) by water, wind, or ice.
 Deposition builds up new land on Earth’s surface, like a delta
at the end of a river or the pile up of a sand dune in the
desert.
 Shells on the beach are deposition by ocean waves.
FORCES
Constructive
Destructive
• Processes that create
• Processes that destroy
landforms (deposition,
landslides, volcanic
eruptions, floods)
landforms (weathering,
erosion, landslides,
volcanic eruptions,
earthquakes, floods)
Earthquakes
 Earthquakes are vibrations on Earth’s surface caused by sudden
movement in Earth, often along a fault, a break in Earth’s
surface.
 Some earthquakes cause little damage and some cause a lot of
damage.
 Large earthquakes can cause landslides.
 Earthquakes under the ocean can cause huge waves, called
tsunamis that destroy land and cause great damage if they
come ashore.
Tsunami
These earthquakes created faults.
Who can tell me what a fault is?
Volcanic eruptions
•Volcanoes are mountains with openings in Earth’s crust
through which magma, gases, and ash reach Earth’s surface.
•Volcanoes can change Earth’s surface.
•When the magma erupts from the volcano the top of the
mountain can be changed, either built up or exploded off.
•The lava and ash can destroy forests and bury fields.
Volcanoes cont…
•Volcanic eruptions can even change Earth’s weather
patterns.
•Volcanic eruptions also occur under the oceans; these
volcanoes that are built up are called seamounts.
•If the seamount rises above the ocean surface it is
called a volcanic island (for example Hawaii or Japan).
Cooled magma creates
solid landmasses
Landslides
Landslides are mass movements of land due to gravity.
 Landslides can cause buildings to fall, or power and gas
lines to break.
 Landslides even occur on the continental slope in the
ocean.
Tsunamis
 Sometimes giant sea waves, called tsunamis,
are caused by underwater earthquakes,
volcanic eruptions, or landslides.
Floods
Floods occur when a large amount of water covers
land that is usually dry.
 When the flood occurs, rapid erosion can take place and move
soil and sediments away.
 When the flood recedes (goes away), new sediment (dirt) is left
behind and can build up rich soil deposits.
Constructive vs. Destructive
Constructive
Processes that
create landforms
Destructive
Processes that destroy
landforms
EXAMPLES:
*Deposition
*Landslides
*volcanic eruptions
*Floods
EXAMPLES:
*Weathering
*Erosion
*Landslides
*Volcanic eruptions
*Earthquakes
*Floods
Deposition is a process that…
A. Dissolves sediment
B. Breaks down rock to form sediment
C. Removes sediment from landforms
D. Drops sediment to form landforms
Where do deltas form?
A. In desert areas
B. At river mouths
C. On the banks of rivers
D. In valleys formed by glaciers
A river overflows due to excessive rains, and floods
surrounding areas. After the rain stops, the water
returns to the river’s original path. However, the
surrounding land is now covered with new soil. This is
an example of….
A. deposition of sediment – a
destructive force
B. deposition of sediment – a constructive
force
C. erosion – a destructive force
D. erosion – a constructive force
Volcanoes can create new
land when they release…
A. Lava
B. Water
C. Gas
D. Mud
What is weathering?
A. A type of climate
B. The transport of sediment
C. The breakdown of rock
D. The aging of rock
Tsunamis are caused by…
A. hurricanes
B. a very large high tide
C. underwater earthquakes
D. the migration of whales
How do earthquakes change
the land?
A. They transport sediment.
B. They form cracks in the surface.
C. They release ash and lava.
D. They cause chemical weathering.
Which is an example of deposition?
A. acids that eat into rock
B. wind building up sand dunes
C. rivers wearing down mountains
D. plant roots breaking apart rock
Which is not a type of physical
weathering?
A. Roots breaking rock
B. Ice Breaking rock
C. Wind and water
D. Chemical Changes
What does erosion do?
A. breaks down rock physically
B. moves broken pieces of rock
C. changes rock chemically
D. change sediment into rock