Earth Changes
Do you know what’s inside the earth?
Do you know how many layers make up our earth?
Let’s Journey to the Center of the Earth!
First Stop:
The Crust
Earth’s thinnest
layer
5 – 70 km thick
Made up of basalt
and granite
Even oceans sit on
the crust!
The crust is broken
into many
pieces called
tectonic plates (but
more about them
later)
Next Stop: The Mantle
A rocky layer under the crust.
The crust actually floats on the mantle.
The mantle is the thickest layer of the earth.
The mantle is solid, but very hot making it soft like melted candy.
This melted candy like part of the mantle is called magma
Convection (heat) currents
carry heat from inner mantle to the cooler outer mantle.
Third Stop:
Outer Core
Made mostly of
molted iron and nickel
Molted means that
something is so hot it
is liquid!
Movement of these
melted metals causes
earth’s magnetic field.
Final Destination: Inner Core
Hottest layer of earth!
Also made of iron and nickel.
No longer liquid because of great pressure.
Tectonic Plates
The cracked pieces of the
earth’s crust!
12 major plates make up
the earth’s crust.
They float on the mantle
and are constantly moving!
Sometimes these plates
crash into each other!
Plate Boundaries
The edges of plates – like a puzzle
German scientist, Alfred Wegener, hypothesized that
200,000,000 years ago, Earth’s continents formed one
large land mass or supercontinent called Pangaea
One vast
(really big)
landmass
or
continent!
By the way,
do you
know the
continents
?
Eventually, because of the tectonic plate movement, this
supercontinent broke apart and is still moving today. This is the
Continental Drift Theory!
Back to plate movement…….
Collision of Tectonic Plates
When plates collide, things happen…..
New landforms are produced like mountains and valleys!
Volcanoes erupt!
Earthquakes occur!
4 Types of Plate Boundaries
Convergent
3 major types of plate boundaries!
Subduction
Divergent Boundaries
Plates separate – move away from each other.
Divergent Boundaries
Effects: volcanoes, mid ocean ridges, rifts (valleys)
and sea floor spreading
Convergent Boundaries
Plates collide into each other – they move toward each other
Convergent Boundaries
Effects: Mountains, volcanoes, and trenches.
Subduction Boundaries
One convergent plate slides under another plate
Transform Boundaries
Two plates slide past each other, but sometimes not so
easily!
When the plates get stuck, they cause an earthquake.
Note: Other boundaries can also sometimes cause earthquakes.
Let’s Review Plate Boundaries
Convergent
Now back to the hot stuff!
Volcanoes!
Types of plate collisions
that cause volcanoes:
Convergent/Subduction
and Divergent
Some volcanoes ooze
and others erupt with a
big bang!
When the mantle’s
magma reaches earth’s
surface, it is called lava.
Ring of Fire
A ring of volcanoes located around the Pacific Ocean
75% of earth’s land volcanoes can be found here!
Over 450 volcanoes!
Basic Structure
3 Major Types of Volcanoes
Composite Cone (Strato volcanoes)
Cinder Cone
Shield Cone
Rocking and Rolling!
Earthquakes
Can you guess which type of plate collision causes earthquakes?
It’s the Transform Plate’s “Fault!”
Earthquake - a violent shaking of the ground caused by the sudden snap
and release of energy in the earth’s crust due to the sliding movement
of two transform plates.
Fault – the location where 2 transform plates meet
In the USA, there is a large fault in California – San Andreas Fault
Where there are faults – there can be earthquakes!
Epicenter
Location on Earth directly above where the earthquake starts.
You don’t want to be here when it happens!
Measuring
Earthquakes
Richter Scale
calculates
how much
energy is
released
during an
earthquake
Seismograph
A machine that can detect released energy from the earth.
Measures the earthquake’s energy.
The World’s first seismograph
Made in China in 132 A.D.
Occur when the earthquake is in the crust under the ocean
Whether or not the earth likes it….
I wonder whether
It weathers!
or not it will be bad
weather
tomorrow?
That’s so
lame Ms.
Sims!
Weathering – the breaking down of rocks
Weathering
the breaking down of rocks into silt, sand, clay, and
other tiny pieces called sediment.
Erosion
The movement of rocks or soil
(sediment) from one place to
another
by wind, water, ice or gravity.
Three types of weathering
1. Physical or Mechanical – When wind, water, ice, or gravity breaks rocks into smaller pieces.
2. Chemical – When a substance changes the molecules and atoms.
Example: when acid rain changes the color of rocks.
3. Biological – When plants or animals effect the landscape.
Example: lichens and color/overgrazing, leaving soil open to erosion by wind, tree roots
breaking apart rocks.
Acid Rain
Lichens
Overgrazing
4 main agents/reasons of
physical weathering
1.
2.
3.
4.
Water
Wind
Ice
Gravity
Water can carve out canyons
Ocean waves can wear away cliffs
Rain can seep into rocks eventually breaking them apart
Flowing water can break down rocks into tiny pieces known as
SEDIMENT
Wind
Wind carries sediment which then acts like a sand
blaster to rock surfaces.
Wind causes sediment to shift, sometimes making
sand dunes.
This is rock, not sand!
ICE
Glaciers are large
masses of ice
When glaciers move,
they carry sediment
with them and
deposit the sediment
into a new location.
Freeze-Thaw Cycle
Gravity
The Story of the Loose Rock…
Once upon a time
I was a large rock,
but then one day
I fell.
I broke into pieces.
I was carried off by
the wind,
then erosion,
then water.
Now, I’m not half the rock I used
to be!
The End.
Mass Movement!
The downhill shifting of rocks, soil, and sediment due to gravity
Example: mudslide
Deposition
Dumping of a load of sediment to a new location.
When the deposition occurs at the mouth of a river it is called a DELTA.
The End