Download Tectonic Plate Boundaries

Our Amazing Planet
Planet Earth
• Earth’s Layers
Crust
• Earth’s thin outermost layer.
–Continental Crust (land) - thick low
density rock (granite).
–Oceanic Crust (sea floor)- thin dense
rock (basalt)
Mantle
• Earth’s thickest layer made of dense
iron-rich super heated soft rock.
• Where convection currents occur.
Core
• Earth’s innermost layer made of hot,
dense iron and nickel.
–Outer core - Liquid
–Inner core - Solid
Lithosphere
• Earth’s outermost layer
• Includes the crust and solid upper part
of the mantle.
• Divided into huge pieces called
“Tectonic Plates”.
• Move around on top of the
asthenosphere - very hot, soft layer of
the mantel.
Earth’s Tectonic Plates
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
• Similar fossils records
• Similar rocks and minerals
• Similar rock formations and striations
• Similar climatic conditions – Glaciations
Evidence of Pangaea
Continents Fit Together
South America and Africa
Similar Fossil Records
Similar Mountain Ranges
Similar Rocks
Rock Striations Match
Other Evidence - Glaciations
Sea Floor Spreading
• Occurs where tectonic plates spread
apart at Mid Ocean Ridges
• Magma rises from inside the Earth
creating new sea floor.
• New sea floor pushes the existing sea
floor out 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-Atlantic Ridge
Convection Currents
in the Mantle
• Causes Sea Floor
Spreading
– The main cause of
plate tectonics
• Convection Currents
– Hot magma rises
and cooler magma
sinks in the
Earth’s Mantel
Tectonic Plate Boundaries
Convergent Boundaries
• Tectonic plates
collide -
• Forms trenches,
mountains, and
subduction zones
• CTMS – Convergent –
trenches – mountains subduction
Convergent Boundaries
Subduction Zones
Creates trenches in the ocean and
mountains and volcanoes on land
Divergent Boundaries
• Tectonic plates move
apart
• Forms Mid Ocean
Ridges in oceans and
Rift Valleys on land
• East African Rift
• Mid-Atlantic Ridge
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
Transform Boundaries
• Tectonic plates slide
past each
• Forms Fault lines
• San Andreas Fault in California
Volcanoes and Earthquakes
Most Occur at Tectonic Plate Boundaries
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.
Hot Spots
• Areas in the middle of tectonic plates
where magma inside the Earth rises
through the crust and forms volcanoes.
• Like the Hawaiian Islands
Hawaii Islands
Super Volcano
• Yellowstone National park
– Underground volcano caused by
another Hot Spot
• 3 overlapping calderas underground is
believed to have formed from a hot spot
creating Yellowstone’s “Super Volcano”
Yellowstone