What is the Theory of Plate Tectonics? • It states that pieces of

Earth’s lithosphere are in a slow, constant motion, driven by convection currents in the mantle.

• As the plates move, they collide, pull apart, or grind past each other, producing spectacular changes in Earth’s surface. These changes include volcanoes, mountain ranges, and deep ocean trenches.

http://w3.salemstate.edu/~lhanson/gls110/GLS110_BasicConcepts.htm

Plate Boundaries • The places where these lithospheric plates come together are

called plate boundaries

• There are three types: divergent boundaries, convergent

boundaries, and transform boundaries.

• A different type of plate movement occurs along each type of

boundary.

What is a divergent boundary?

• Divergent Boundary: where two

plates move apart

What happens at divergent boundaries?

• #1. If two oceanic plates

move apart, then a mid-

ocean ridge is formed.

EX: Atlantic Mid-Ocean

Ridge

• #2. If two continental

plates move apart, then a

rift valley is formed. EX:

Great Rift Valley in Africa

This happens because… • Molten material fills in the space

left between the two plates to form

new land.

We can see this above water in Iceland!

Hydrotherma vents along mid-ocean ridges!

Smokers

Can things live in this superheated environment?

Tubeworms, palmworms,

scale worms and limpets

thrive in warm, diffusely

flowing vent fluids issuing

from the black smoker

chimney "Finn" on the Juan

de Fuca Ridge

Complex

communities

fueled by the

chemicals

dissolved in

the vent fluids

What is a convergent boundary?

• Convergent

boundary: place

where two plates

come together.

• The result is a

collision where the

density of the plate

determines what

happens.

http://www.divediscover.whoi.edu/images/tectonics-collide.jpg

Convergent Boundary #1 • If an oceanic plate

meets a continental

plate then the

oceanic plate is

subducted and

volcanoes are

formed.

• This happens

because the oceanic

plate is more dense.

Convergent Boundary #2 • If two continental

plates collide (equal

density), mountains

are created.

• EX: Himalayas

Convergent Boundary #3 • If two oceanic plates collide then the

plate that is more dense will subduct

into the mantle through a deep-ocean

trench.

What is a transform boundary?

• A boundary where two plates grind past each other without the production or destruction of lithosphere.

• A fault is created. EX: San Andreas Fault

• Notice subduction zone…

When it comes to the Earth,

it’s like a rug…

http://rst.gsfc.nasa.gov/Sect2/Sect2_6.html

• Over millions of years, the forces of plate

movement can change a flat plain into

landforms such as anticlines and synclines,

folded mountains, fault-block mountains, and

plateaus.

Folding Earth’s Crust • This results in

mountains and

plateaus. EX:

Colorado Plateau

Rockies were never volcanoes.

Divergent Convergent Transform