Download Constructive and Destructive Landforms

Two Types of Forces
 Destructive Forces: processes that destroy
landforms.
 2 types: Slow (weathering) and Fast (Erosion)
 Ex. landslides, volcanic eruptions, earthquakes, floods
 Constructive forces: forces that build up an
existing landform or create a new one.
 Caused by: water, gravity, wind and glaciers.
 Ex: deposition, landslides, volcanic eruptions, floods
Weathering
 Weathering is the breaking down of rocks into smaller
pieces.
 Rain, ice, and atmospheric gases cause this.
 Physical/ Mechanical weathering
 Rocks are broken into smaller pieces by physical agents.
 Ice wedging.
 Plant and animal actions.
 Water
 Chemical weathering
 Breaking down of rocks due to the chemical change in
their composition.
 Air and water often cause this.
 Oxidation (rust) and acid rain.
Erosion
 The process that moves rock material at Earth’s surface
and caries it away.
 Movement of the rock particles.
 Causes of erosion…
 Gravity-landslides/rockslides.
 Running water-rivers form canyons
 Groundwater-underground water forms caves/caverns
 Glaciers-rocks are carried under a glacier.
 Wind-rock particles are blown
 Ocean currents-sand is moved along a beach by waves.
Constructive Landform Processes
 Processes that build up Earth’s surface and cause the
land surface to rise.
Deposition
 The process by which eroded material is dropped off or
deposited in a new area.
 Gravity
 Water
 Wind
 Glaciers
 Ocean currents
Volcanic Eruptions
 Volcano: ???
 an opening in the
Earth’s crust through
which steam, lava and
ashes erupt.
 Cause both destructive
and constructive
changes to landforms.
Volcanoes can be constructive, but also
destructive…
Folding and Faulting
 Forces in Earth’s surface caused by the movement of
Earth’s plates squeezes and bends the surface of Earth.
 Folding occurs when the crust is bent upward or
downward.
 Faulting occurs when the crust is actually broken.
Volcanic Activity
 The movement of liquid rock underground and on
earth’s surface.
 Magma is hot liquid rock beneath the Earth’s surface.
 Magma is less dense than solid rock so it rises to the
surface.
 This forms a volcano.
 When volcano’s erupt, they release hot liquid rock
called lava.
 Lava will harden forming new landforms.
Mount St. Helens
Saint Helen’s Before
Saint Helen’s After
Earthquakes
 Earthquakes: the
shaking of Earth’s
surface caused by the
release of energy along
a fault.
San Andreas Fault, California
Volcanoes & Earthquakes
Tectonic Plates, Volcanoes & Earthquakes
Landforms from Erosion
 Canyons/valleys
 Flowing water removes sediment.
 Sea cliffs
 Waves erode rock making steep cliffs.
 Sea caves, arches, and stacks.
Landforms from Deposition
 Flood plains
 Sediments deposited when rivers overflow their banks.
 Deltas and Alluvial Fans
 When a stream flows into a large body of water
(lake/ocean) or onto land, it deposits sediment in a fan
shape.
 Delta-fan shaped pattern in a lake or ocean.
 Alluvial fan-fan shaped pattern on land.
Water Erosion & Deposition
 River Delta- Deposits of
sediment at the mouth
of the Mississippi River
creating new land
called a delta.
 Beaches
 Area of shoreline made up of sediment deposited by
ocean currents and waves.
Landforms from Folding and
Faulting
 Block mountains
 Large areas of Earth are forced upwards in a fault.
 Rift valley
 When two pieces of Earth’s surface are separating from
each other.
 Folded mountains
 When the surface of Earth is bent upward making a
mountain.
Landforms from Volcanic
Activity
 Volcanoes
 Dome mountain
 Magma forces the surface of Earth up into a dome
shaped mountain.
 Plateau
Primetime
 What are two examples of destructive forces?
 What are four examples of constructive forces?
 Give an example where constructive and destructive
forces work together to create a landform.