Constructive & Destructive Forces - Fifth Grade · •Magma – Below ground, Higher temp. •Lava...
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Transcript of Constructive & Destructive Forces - Fifth Grade · •Magma – Below ground, Higher temp. •Lava...
Intro:
• Constructive Forces
– Processes that create landforms.
• Destructive Forces
– Processes that destroy landforms.
Intro:
• Constructive Forces
– Volcanoes
– Deposition
– Landslides
– Floods
• Destructive Forces
_Weathering/Erosion
– Volcanoes
– Landslides
– Earthquakes
– Floods
Weathering:
• Process that breaks down rock &
other substances at the Earth’s
surface
• Temperature, water, wind, and plants
all contribute to weathering
Physical Weathering:
• Rock is physically broken into
smaller pieces.
• Small pieces have same
composition as the original rock.
• Very slow
Chemical Weathering:
• Breaks down rock through chemical
changes
• Rock particles have different mineral
make-up than original rock
Erosion:
• Process by which natural forces move
weathered rock & soil from one place to
another (by wind, water, waves, ice, &
gravity)
• Sediment
• Material moved by weathering/erosion
Deposition:
• Deposition is the dropping, or depositing,
of sediments 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 of a sand dune in the desert.
• Shells on the beach are deposition by
ocean waves.
Earthquakes:
• Earth is made of layers.
• The crust is the thinnest layer.
• The crust is made up of giant slabs of
rock called plates.
• When plates move, earthquakes may
occur.
Earthquakes:
• Earthquakes are movements in
Earth’s crust that are caused by a
sudden shift of Earth’s plates.
• Destructive force
• Mountains and volcanoes form as
plates move.
Where Earthquakes Happen:
• Most earthquakes occur near the
edges of Earth’s plates.
• There is an area around the Pacific
Ocean where some of Earth’s plates
meet.
• It is here that most earthquakes
happen.
What causes an earthquake:
• Plates are always moving.
• Sometimes, they move slowly.
• At other times, the motion is sudden.
• The energy released by the sudden
motion of plates shakes the crust.
• It can set a large earthquake in
motion.
What is a Tsunami?
A tsunami – is a giant ocean wave.
• Tsunamis are usually caused by
earthquakes on the ocean floor.
• A few are caused by underwater
landslides and volcanoes.
• Can move faster than 700 m/hr.
Volcanoes:
• Destructive AND Constructive
• Weak spot in the crust where molten
material from the mantle comes to the
surface
• Magma – Below ground, Higher temp.
• Lava – magma that reaches the
surface
What is a volcano?
• A volcano is a mountain that builds up
around an opening in the Earth’s
crust.
• Sometimes, melted rock, gases, and
pieces of rock are forced out of the
volcano.
• This is called an eruption.
Where do volcanoes begin?
• When Earth’s plates move, sometimes they bump into each other.
• As a result, one plate is pushed down deeper inside the Earth.
• When this happens, magma is pushed to the surface.
• This can cause a volcanic eruption.
Locations of Volcanoes:
• There are many volcanoes along the
edge of the Pacific Plate.
• Ring of Fire – Major belt of volcanoes
that encircles most of the Pacific
Ocean
Parts of a Volcano
Crater – bowl shaped
area that forms around a
central vent
Vent – opening
through which
molten rock & gas
escape
Side Vent Pipe – long tube
through which
magma moves
from the magma
chamber to the
surface
Magma
Chamber
beneath a
volcano where
magma
collects
Effects of Volcanic Eruptions:
• The lava and ash can destroy forests
and bury fields.
• Volcanic eruptions can even change
Earth’s weather patterns.
Volcanic Eruptions on the
Ocean Floor:
• Volcanic eruptions, called seamounts,
can 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.)
Types of Volcanic Eruptions:
2. Explosive –
- Thick & sticky magma plugs up the
pipe where pressure builds up
- Breaks lava into pieces that quickly
cool & harden
- Ash, cinders (pebbles), & bombs hurled out
- Mt. Saint Helens
Volcano All-Stars:
• Mt. Saint Helens –
- Washington state
- Erupted May 18, 1980
- Leveled trees for 25 miles (Pyroclastic
flow)
Mass Movement:
• Caused by gravity
• Process that moves sediment downhill
• 4 types
– Landslide - Slump
– Mudslide - Creep
Landslide:
• 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.
Flood:
• A large amount of water covers the
land. It can cause rapid erosion
(destructive), but also deposition
(constructive).