Plate Interactions What do you think we might see at a plate boudary? What might we feel?

Plate Boundaries Region where two tectonics plates are in contact. What boundary are we next to? See: Ridges, Trenches, Action felt: volcanoes, earthquakes

1) Divergent Boundaries Plates spread apart As lava surfaces, new crust is formed.   mountain ranges on bottom of the ocean (mid-ocean ridges);  continental rifts on land As tectonic plates move they sometimes move away from each other at divergent plate boundaries. The space left behind opens a large hole between the plates that is either filled with sediment, magma flowing from the mantle, or water. The major difference between different types is what type of plate the divergent boundary is between.  If the boundary is found between two continental plates you are left with a rift valley. This leads to steep mountainsides spreading apart from a widening valley. In the center of the valley either large gaps can form or the area will fill with water from water sources or rain creating rift lakes, much like what can be found in the African Rift Valley. Many lakes have sprung up in the valleys left behind as the plates there move slowly away from each other.  If two oceanic plates begin moving away from each other it creates a mid-oceanic ridge. Continental plates are less dense, and thus float much higher on the mantle. Magma is usually much farther away, so it's rare to find a splitting continental plate seeping magma. On the other hand, oceanic plates are thin and dense, meaning magma is much more likely to flow to the surface at one of these splits. At the Mid-Atlantic Ridge, the boundary between the North American plate and the Eurasian plate, the spreading boundary is constantly seeping hot magma out of the mantle below. This creates a constantly growing mountain chain.  The main difference between these two seismic structures would be what types of plates are creating the diverging zone and what is being created at the divide: a valley that may fill with water or sediment, or a growing mountain chain as magma fills the opening gap.

Divergent Boundaries Eg. Mid-Atlantic ridge Mid-Atlantic -largest mountain range

Divergent Boundaries Eg. Endeavour hydrothermal vents were created as the Juan de Fuca plate moves away from the Pacific plate

Diverging Boundaries Can also occur in middle of continents (continental rifting)

2. Convergent Boundaries - Where two plates collide variable results depending on the plates involved…3 types

a) Continental-Oceanic Plates More dense oceanic plate subducts under less dense Continental crust. Continental crust never subducts because it is less dense than oceanic crust.  Earthquakes  Ocean Trenches  Sometimes volcanoes  Volcanic Island Chains Trench forms Sometimes volcanoes

a) Continental-Oceanic Plates - Features Pockets of magma develop and rise: Continental volcanic arcs form in part by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent. Eg. Andes Mountain Range, Cascades, and the Sierra Nevadas. Trench forms Sometimes volcanoes

Eg. Cascade Mountain Range Mount Garibaldi Mount Meager Although plates move slowly, great forces are involved. Colliding plates may resist the force of convection currents, ridge push and slab pull. Pressure builds as long as the plate remain stuck in place. When te stress is too great, energy released in earthquake.

b) Oceanic-Oceanic Plates Usually one plate subducts beneath the other. Volcanoes Volcanic Island Arcs Ocean Trenches Deep Earthquakes chain of volcanic islands=volcanic island arc subduction zone is the biggest crash scene on Earth. These boundaries mark the collision between two of the planet's tectonic plates. The plates are pieces of crust that slowly move across the planet's surface over millions of years. here two tectonic plates meet at a subduction zone, one bends and slides underneath the other, curving down into the mantle. (The mantle is the hotter layer under the crust.)  Tectonic plates can transport both continental crust and oceanic crust, or they may be made of only one kind of crust. Oceanic crust is denser than continental crust. At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust. (Sometimes, oceanic crust may grow so old and that dense that it collapses and spontaneously forms a subduction zone, scientists think.) 

Eg. Aleutian Islands of Alaska

c) Continental-Continental Plate Convergence Neither plate is dense enough to be pushed down, so the land buckles like a car hood in a car crash (“uplifting”), Subduction does not occur due to similar densities. If the same kind of crust collides, such as continent-continent, the plates may crash together without subducting and crumple together like crashing cars. The massive Himalaya mountain chain was created this way, when India slammed into Asia.

c) Continental-Continental Plate Features Mountain Ranges Eg. Himalayas formed from Indian continent colliding with Asian continent.  Youngest and highest mountain range Continue to increase in elevation by several cm per year  Subduction does not occur due to similar densities. If the same kind of crust collides, such as continent-continent, the plates may crash together without subducting and crumple together like crashing cars. The massive Himalaya mountain chain was created this way, when India slammed into Asia.

3) Transform Boundaries Where two plates grind past each other without destroying the lithosphere. Results in frequent earthquakes and faults (fracture in the crust) No mountains or volcanoes First identified by Canadian geologist, John Tuzo Wilson.

Transform Boundary Eg. San Andreas Fault, California

Practice: Snack Tectonics

Extras

3) Transform Boundaries Mostly occur near ocean ridges Oct 2012, an earthquake of magnitude of 7.7 originated from movement along the Queen Charlotte Fault. the boundary between the Pacific Plate and the Australian Plate, crossing New Zealand the boundary between the Pacific Plate and the North American Plate in California

Check your Understanding Name and draw three main types of tectonic plate boundaries. Why does subduction not occur at some kinds of tectonic plate boundaries? Describe the process that results in a volcanic island arc. Name a mountain range produced by continental- continental plate convergence.

Homework Snack Tectonics Activity

Extra

All 3 types of plate boundaries exist in BC Transform: Pacific Plate grinds past NA Plate at Queen Charlotte Fault (earthquakes) Divergent: Juan de Fuca Ridge sea floor spreading Convergen : Great Earthquakes in BC every 200-800 years. First Nations recount one of the lartgest in the world on Jan 26, 1700. collapse houses of the Cowichan peplel; on Vancouver Island and produced a tsunami that destroyed a village a Pachena Bay . Tsunami travelled across the Pacific Ocean and cuased damage in Japan

Volcanoes of our West Coast: are result of convergence between  Juan de Fuca Plate (oceanic) and North American Plate (continental).

Eg. Cascade Mountain Range Mount Garibaldi Mount Meager Although plates move slowly, great forces are involved. Colliding plates may resist the force of convection currents, ridge push and slab pull. Pressure builds as long as the plate remain stuck in place. When te stress is too great, energy released in earthquake.

Pacific Ring of Fire The Ring of Fire is a string of volcanoes and earthquakes, around the edges of the Pacific Ocean. Roughly 90% of all earthquakes occur along the Ring of Fire, 75% of all active volcanoes on Earth.  The island nation of Japan lies along the western edge of the Ring of Fire, and is one of the most tectonically active places on Earth. As much as 10% of the world’s volcanic activity takes place in Japan.

Plate Boundary Symbols

All 3 types of plate boundaries exist in BC Transform: Pacific Plate grinds past NA Plate at Queen Charlotte Fault (earthquakes) Divergent: Juan de Fuca Ridge sea floor spreading Convergen : Great Earthquakes in BC every 200-800 years. First Nations recount one of the lartgest in the world on Jan 26, 1700. collapse houses of the Cowichan peplel; on Vancouver Island and produced a tsunami that destroyed a village a Pachena Bay . Tsunami travelled across the Pacific Ocean and cuased damage in Japan

Check your Understanding Name and draw three main types of tectonic plate boundaries. Why does subduction not occur at some kinds of tectonic plate boundaries? Describe the process that results in a volcanic island arc. Name a mountain range produced by continental- continental plate convergence.

How can we know how hot it is? https://www.youtube.com/watch?v=mOSpRzW2i_4

How deep can we go? https://www.youtube.com/watch?v=E39GIysMevQ

In your own words describe continental drift hypothesis How did Wegener support his hypothesis ? Why do you think he chose this type of information? Why was the continental drift hypothesis rejected?

Check your Understanding In your own words describe Continental Drift Hypothesis How did Wegener support his hypothesis? Why do you think he chose this type of information? Why was the continental drift hypothesis rejected?

Check your understanding What is the difference between the Theory of Continental Drift and the Theory of Plate Tectonics?

Check your understanding What is the difference between the Theory of Continental Drift and the Theory of Plate Tectonics? Continental Drift was proposed first and only states (but does not explain) the splitting up of Pangaea in the current seven continents. Plate Tectonics explains Continental Drift, and also other geologic features such as volcanoes, earthquakes, mountains etc,