Chapter 10 – Plate Tectonics
Keyterms
Section I - Continental Drift
 Super continent – Landmass formed by all continents (which were once together)
 Continental Drift Theory – Theory that states that the continents once formed a single landmass and slowly
drifted to their present location
 Father of Continental Drift Theory – Alfred Wegener
 Evidences for Continental Drift Theory (4)
o Continents fit like puzzle pieces
o Climatic Evidence – Tropical plants in Antarctica; Evidence of glacier erosion in tropical areas
o Fossil Evidence – Same animals on different continents
o Rock formations – Rifts and mountain ranges start on one continent and continue on the next.
 Fossils – Petrified imprints of dead organisms on rock
 Rock formations – Shapes of rocks (Mountains / Rifts / Valleys)
 Climatic Evidence – Tree rings; ice cores;
 Reason why Continental Drift Theory was initially discarded – Wegener Had enough evidence for it, but no
mechanism (could not explain HOW it happened)
 Mid-Ocean Ridge – Pair of parallel mountain ranges at the center of a growing ocean
 Rift – A crack on the lithosphere that allows magma to rise from the mantle to the surface
 Sediment – Rock debris and remains of dead animals that gather at the ocean bottom over the years
 Oceanic Crust – Dense-magnesium/iron rich piece of the Earth’s lithosphere that is underneath the oceans and
thinner than continents.
 Continental Crust – Less dense silicon/oxygen rich piece of the Earth’s lithosphere that make up the
continents and is thicker than oceanic crust
 Magma – Molten rock underneath or within the geosphere (not touching air/water)
 Lava – Molten rock above the lithosphere (exposed to water/air)
 Sea floor spreading – Process by witch new oceanic lithosphere (sea floor) forms as magma rises to the Earth’s
surface and solidifies at the mid-Ocean ridge.
 Paleomagnetism – the study of the magnetic alignment of magnetic minerals in rock
 Normal magnetic rock polarity – Magnetic minerals in rock aligned towards the North pole
 Reverse magnetic rock polarity –Magnetic minerals in rock aligned towards the South pole
 Magnetic symmetry – Alternating pattern of reversals of magnetic polarity of rocks on one side of the midocean ridge is mirrored on the opposite side
 Geomagnetic reversal time scale – Alternating pattern of reversals of magnetic polarity of rocks on either side
of the mid-ocean ridge, which serves as a timeline of development of the sea floor.
Section II – Theory of Plate Tectonics
 Plate Tectonics – The theory that explains how large pieces of the lithosphere, called plates, move and change
shape
 Lithosphere – the solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle
 Asthenosphere – the solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows
very slowly, which allows tectonic plates to move on top of it
 Oceanic Crust – Dense-magnesium/iron rich piece of the Earth’s lithosphere that is underneath the oceans and
thinner than continents.
 Continental Crust – Less dense silicon/oxygen rich piece of the Earth’s lithosphere that make up the
continents and is thicker than oceanic crust
 How many plates - 15
 How to locate boundaries (2) – Mountain ranges/trenches & earthquakes/volcanoes
 Earthquakes – Sudden movements within pieces of the lithosphere associated with tectonic plate motion
 Volcanoes – Locations where magma rising on cracks on the lithosphere reaches the surface (becomes lava)
 Ring of Fire – Zone of active volcanoes that encircles the Pacific Ocean
 Divergent Boundaries – Boundary between tectonic plates that are moving away from each other
 Mid-Ocean Ridge – Pair of parallel mountain ranges at the center of a growing ocean
 Rift valley – Valley formed in between each of the mountain ranges of the mid-ocean ridge
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Convergent Boundaries – Boundary between tectonic plates that are moving towards each other, or colliding
Subduction zone – Region along a plate boundary where one plate moves under another plate
Mountain Ranges – Series of rock folds in the lithosphere that rise to form a chain of mountains
Rock Faults – Cracks on rocks (i.e. Faults
Rock Folds – Bending of rocks (i.e. Mountains / Valleys)
Island Arc – Chain of volcanic islands formed near convergent boundaries (essentially a mountain range that
rises from the sea floor to the above the water surface)
Transform Boundaries – The boundary between tectonic plates that are sliding past each other horizontally
Fracture zone – Short segments of a mid-ocean ridge connected by transform boundaries
Convection – Heat transfer through movement of heated particles (particles carry the heat as they move)
Convection cell – Heated particles are less dense and rise; They cool down as they rise until they are cold
enough to become denser and sink; As they sink they again approach the heat source and heat up; This restarts
the cycle (best thing to do is to draw a picture)
Mantle convection – Core heats up the bottom of the mesosphere; hot material rises; hot material loses heat by
conduction to the asthenosphere & lithosphere; now colder, the material sinks; Once it sinks all the way down
to the bottom, it is once again heated by the core (best thing to do is to draw a picture)
Ridge Push – Force exerted near the rift of mid-ocean ridges when cooling rock sinks and pushes the rest of the
plate away from the rift
Slab Pull –Force exerted by sinking plate (pulls the rest of the plate with it)
Section 3 – Changing Continents
 Cratons – Large areas of old/stable rock (like most of the continental crust)
 Shields – Rocks within cratons exposed to the surface
 Rifting – The process by with Earth’s crust breaks apart (can occur within continents or oceans)
 Terrane – A piece of lithosphere that has a unique geologic history and that may be a part of a larger piece,
such as a continent (i.e. Sea mounts, attols, large pieces of crust that broke off a continent)
 Accretion – Process by which a terrane becomes part of a continent (Like India merging with Asia)
 Seamounts – Small volcanic islands at the sea floor
 Attols – Small coral islands
 Climate – Long term pattern of atmospheric conditions
 Supercontinent Cycle – The process by which supercontinents form and break apart over millions of years
 Pangaea – The supercontinent that formed 300 million years ago and that began to break up 250 million years
ago
 Panthalassa – The large single ocean that covered Earth’s surface during the time that the supercontinent
Pangea existed
 Gondwanaland – One of the two initial continental pieces that formed from the breaking up of Pangea (what is
now South America, Africa, India, Australia, & Antarctica were part of it)
 Laurasia – One of the two initial continental pieces that formed from the breaking up of Pangea (what is now
Asia, North America, & Europe were part of it)
 How long since last supercontinent – 250 millions years
 Thethys Sea – Ocean formed between Panthalassa & Gondwanaland after the first first rift broke Pangea apart
 Alps – Mountain range formed when the terrain where Italy is collided with Europe
 Ural Mountains – Mountain range formed by collision between Eurasia plate and the plate that carries the
Middle East (Kazakhstania)
 Rocky Mountains – Mountain range formed by the collision between the North American and pacific plates
 Andes – Mountain range formed by the collision between South American and Nazca plate
 Himalayas – Mountain range formed by collision between India’s terrain and Asia