Features of Plate Tectonics

Science 10

Layers of the EarthCrust• outer layer – thinner under oceans than under

continents• Broken into plates

Mantle• Thickest layer – upper mantle is partly liquid–

lower mantle is solid rock with Mg and Fe

• Mantle convection occurs in liquid upper mantle

• outer core – liquid Fe and Ni• inner core – solid Fe and Ni – 5000-6000oC

• The crust and part of the upper mantle make up the lithosphere, which is broken into tectonic plates

• The rest of the upper mantle is called the asthenosphere – this is where mantle convection occurs…. These currents are what cause the tectonic plates to move

• Earth’s outer layer made up of separate, rigid slabs called plates

• These plates move at speeds of between 2 cm and 10 cm per year -move due to “convection currents”

Push and PullRidge Push• As magma reaches the surface and cools, it

pushes older material to the side

Slab pull• As a tectonic plate moves beneath a less

dense plate (known as subduction), the plate pulls the rest of the plate with it

Plate Boundaries

• Are regions where two plates interact

• There are 3 main types

Divergent Boundaries• Plates move/pull away from each other

• Example: Mid Atlantic Ridge

• Features include Oceanic/Spreading Ridge (ocean) or Rift Valley (on land)

Convergent Boundaries

• Plates move towards each other and collide.

• 3 possible scenarios:a) Oceanic-continentalb) Ocean-oceanicc) Continental-continental

Oceanic-Continental Convergence

• Oceanic plate slides beneath continental plate because it is oceanic is more dense

• Features include: underwater valleys (trench) and volcanoes (volcanic belt)

• Example location: West Coast of North America

Oceanic-Oceanic• Older, cooler oceanic plate will slide beneath other

plate

• Features include: volcanic island arc

• Example locations: Japan, Indonesia, island of Alaska

Continental-Continental• 2 similar continental plates collide

• Features: Large mountain ranges

• Example locations: Himalayas

Transform Boundaries

• Plates slide past each other

• Features: Breaks in rock called faults and earthquakes

• Example location: California’s San Andreas Fault