Plate TectonicsPlate Tectonics

Joy NowakJoy Nowak

What is plate tectonics?What is plate tectonics?

• A plate is a large, rigid slab of rock.• The word tectonics comes from the

Greek root “to build”.• The Earths surface is built of plates.• The theory of plate tectonics states that

the Earths outermost layer is fragmented into twelve or more large and small plates that are moving relative to one another as they ride atop a hotter, more mobile material.

• A plate is a large, rigid slab of rock.• The word tectonics comes from the

Greek root “to build”.• The Earths surface is built of plates.• The theory of plate tectonics states that

the Earths outermost layer is fragmented into twelve or more large and small plates that are moving relative to one another as they ride atop a hotter, more mobile material.

Ocean and continental plates.

Ocean and continental plates.

• Continental plates are thicker but less dense.

• Ocean plates are thinner but more dense.

• Continental plates are thicker but less dense.

• Ocean plates are thinner but more dense.

Earth’s top layersEarth’s top layers

• Top layer is called the lithoshere, which contains the crust and the uppermost part of the rigid mantle.

• Under the lithosphere is the asthenosphere.

• Asthenosphere consists of of a solid but low viscosity which can make it flow like liquid.

• Below the asthenosphere is the deeper mantle which is more rigid.

• Top layer is called the lithoshere, which contains the crust and the uppermost part of the rigid mantle.

• Under the lithosphere is the asthenosphere.

• Asthenosphere consists of of a solid but low viscosity which can make it flow like liquid.

• Below the asthenosphere is the deeper mantle which is more rigid.

Continental driftContinental drift

• The Earth’s plates are in constant motion.

• The continents that we know today were once one super continent known as Pangaea.

• Over time the continent began to split slowly creating seven continents.

• The Earth’s plates are in constant motion.

• The continents that we know today were once one super continent known as Pangaea.

• Over time the continent began to split slowly creating seven continents.

What drives the plates?What drives the plates?

• Harry Hess’ theory is that the plate-driving force is the slow movement of hot, softened mantle that lies below the rigid plates.

• Moving rock beneath the rigid plates is believed to be moving in a circular motion.

• Harry Hess’ theory is that the plate-driving force is the slow movement of hot, softened mantle that lies below the rigid plates.

• Moving rock beneath the rigid plates is believed to be moving in a circular motion.

• The heated rock rises to the surface, spreads, cools, then sinks back to down. This cycle is called convection cell or convective flow which causes plate movement.

• The plates move very slowly on the surface, only about two inches a year on average.

• The heated rock rises to the surface, spreads, cools, then sinks back to down. This cycle is called convection cell or convective flow which causes plate movement.

• The plates move very slowly on the surface, only about two inches a year on average.

Plate boundariesPlate boundaries

• There are three types of plate boundaries and are characterized by the way the plates move relative to each other.

• Each boundary causes different reactions.

• There are three types of plate boundaries and are characterized by the way the plates move relative to each other.

• Each boundary causes different reactions.

Transform boundaries Transform boundaries

• Plates next to each other slide past each other.

• The plates grind past each other on transform faults causing earthquakes.

• The San Andreas fault in California is a transform boundary that has caused many earthquakes.

• Plates next to each other slide past each other.

• The plates grind past each other on transform faults causing earthquakes.

• The San Andreas fault in California is a transform boundary that has caused many earthquakes.

Convergent boundariesConvergent boundaries

• Two plates slide towards each other causing either a subduction zone or a continental collision.

• A subduction zone is when one plate moves underneath the other which can cause Earthquakes, tsunamis, and volcanic activity.

• Continental collision causes the plates to hit each other and raise above the surface causing mountain ranges.

• Two plates slide towards each other causing either a subduction zone or a continental collision.

• A subduction zone is when one plate moves underneath the other which can cause Earthquakes, tsunamis, and volcanic activity.

• Continental collision causes the plates to hit each other and raise above the surface causing mountain ranges.

Divergent boundariesDivergent boundaries

• Occur where to plates slide apart from each other.

• The separating plates move apart and new crust is created by magma pushing up from the mantle.

• The Mid-Atlantic ridge is a submerged mountain range from the Artic Ocean to beyond the southern most tip of Africa. This was caused by divergent boundaries.

• Occur where to plates slide apart from each other.

• The separating plates move apart and new crust is created by magma pushing up from the mantle.

• The Mid-Atlantic ridge is a submerged mountain range from the Artic Ocean to beyond the southern most tip of Africa. This was caused by divergent boundaries.

SourcesSources

• http://en.wikipedia.org/wiki/Plate_tectonics

• This Dynamic Earth: The Story of Plate Tectonics by W. Jacquelyne Kious and Robert I. Tilling (online book through usgs.org)

• http://pubs.usgs.gov/gip/dynamic/understanding.html#anchor6715825

• http://en.wikipedia.org/wiki/Plate_tectonics

• This Dynamic Earth: The Story of Plate Tectonics by W. Jacquelyne Kious and Robert I. Tilling (online book through usgs.org)

• http://pubs.usgs.gov/gip/dynamic/understanding.html#anchor6715825

• http://volcano.und.edu/vwdocs/vwlessons/lessons/Plates/Plates11.html

• http://www.windows.ucar.edu/tour/link=/teacher_resources/teach_snacktectonics.html

• http://www.astronomynotes.com/solarsys/plates-collide.png

• http://volcano.und.edu/vwdocs/vwlessons/lessons/Plates/Plates11.html

• http://www.windows.ucar.edu/tour/link=/teacher_resources/teach_snacktectonics.html

• http://www.astronomynotes.com/solarsys/plates-collide.png