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Our Amazing Planet
Planet Earth
• Earth’s Layers
Composition (What it’s made of)
• Fill out the Inner Left side of your “Our
Amazing Planet” foldable using the
following slides.
Crust
• Earth’s thin outermost layer.
–Continental Crust (land) - thick low
density rock (granite).
–Oceanic Crust (sea floor)- thin dense
rock (basalt)
Lithosphere
• Earth’s outermost layer
• Includes the crust and solid upper part
of the mantle.
• Divided into huge pieces called
“Tectonic Plates”.
• “Floats” on top of the asthenosphere very hot, soft layer of the mantle.
Asthenosphere- Upper Mantle
• Earth’s thickest layer made of dense
iron-rich super heated soft rock.
-semisolid layer
• *Layer where convection currents
occur.
Convection Currents
in the Asthenospere
• Causes Sea Floor
Spreading
– The main cause of
plate tectonics
• Convection Currents
– Hot magma rises
and cooler magma
sinks in the
Earth’s upper
Mantle
Core
• Earth’s innermost layer made of hot,
dense iron and nickel.
–Inner core - Solid
–Outer core - Liquid
Earth’s Tectonic Plates
Continental Drift
• Fill in “Our Amazing Planet” Foldable on
back left side.
Continental Drift
– Theory that the Earth’s continents move
over time
– Proposed by Alfred Wegener in the early
1900’s
– Evidence of Continental Drift:
• Continents fit together (South America
and Africa)
• Similar fossils found on different
continents
• Similar rocks and minerals
• Similar climatic conditions
Evidence of Pangaea
Continents Fit Together
Eastern coast of South America and
western coast of Africa
Found Fossils!
Mid-Atlantic Ridge
Mid-Atlantic Ridge
Tectonic Plate Boundaries
Convergent Boundaries
• Tectonic plates that
collide or come
together
• A) When two plates
of equal density
collide they squish
together to form
folded non volcanic
mountains.
Convergent Boundaries
Subduction Zones (a process)
B) Difference in density between oceanic
and continental crust creates trenches
in the ocean and volcanoes on land
Divergent Boundaries
• Tectonic plates move
apart or separate
• Forms Mid Ocean
Ridges in oceans and
Rift Valleys on land
• East African Rift
• Mid-Atlantic Ridge
Sea Floor Spreading
(divergent boundary)
• Occurs where tectonic plates spread
apart at Mid Ocean Ridges
• Magma rises from upper mantle creating
new crust (sea floor) .
• New “younger” sea floor pushes the
existing “older” sea floor out (laterally)
explaining why continents move.
–Evidence that supports the theory of
Continental Drift.
Sea Floor Spreading
New crust is formed at mid-ocean
ridges spreading the sea floor
Mid-Ocean Ridges
• Chain of volcanoes at the middle of the
ocean floor.
• Causes Sea Floor Spreading
• Magma comes up from inside the Earth,
cools and hardens and creates new sea
floor.
• The rock at the mid-ocean ridge is the
youngest and gets older as it moves
farther away from the ridges.
Mid-Atlantic Ridge
Rift Valley
(divergent boundary)
There are only two rift valleys on Earth within
continental crust.
-the Baikal Rift Valley and the East African Rift.
- Tectonic activity splits continental crust much in the
same way it does along mid-ocean ridges. As the sides of
a rift valley move farther apart, the floor sinks lower.
Transform Boundaries
• Tectonic plates slide
past each other.
• Forms Fault lines
• San Andreas Fault in California
• Why not in Texas?
Plate Boundary Foldable
Convergent
“Colliding”
• Forms mountains
• Indo-Australian plate
collides with the Eurasian
plate to from the
Himalayan Mountains
Divergent
“Dividing”
• On land forms rift valleys
• In the ocean forms seafloor spreading
• “Mid-Atlantic Ridge”
Transform
“Sliding”
• Causes earthquakes
• San Andreas Fault
Ring Of Fire
Ring of Fire
• Volcanoes around the Pacific Ocean
caused by tectonic plates colliding into
each other creating subduction zones at
CONVERGENT boundaries.
Volcanoes and Earthquakes
Most Occur at Tectonic Plate Boundaries